| Rfc | 5190 |
|---|
| Title | Definitions of Managed Objects for Middlebox Communication |
|---|
| Author | J.
Quittek, M. Stiemerling, P. Srisuresh |
|---|
| Date | March 2008 |
|---|
| Format: | TXT,
HTML |
|---|
| Status: | PROPOSED STANDARD |
|---|
|
Network Working Group J. Quittek
Request for Comments: 5190 M. Stiemerling
Category: Standards Track NEC
P. Srisuresh
Kazeon Systems
March 2008
Definitions of Managed Objects for Middlebox Communication
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
This memo defines a portion of the Management Information Base (MIB)
for use with network management protocols in the Internet community.
In particular, it describes a set of managed objects that allow
configuring middleboxes, such as firewalls and network address
translators, in order to enable communication across these devices.
The definitions of managed objects in this documents follow closely
the MIDCOM semantics defined in RFC 5189.
Table of Contents
1. Introduction ....................................................4
2. The Internet-Standard Management Framework ......................4
3. Overview ........................................................4
3.1. Terminology ................................................5
4. Realizing the MIDCOM Protocol with SNMP .........................6
4.1. MIDCOM Sessions ............................................6
4.1.1. Authentication and Authorization ....................6
4.2. MIDCOM Transactions ........................................7
4.2.1. Asynchronous Transactions ...........................7
4.2.2. Configuration Transactions ..........................8
4.2.3. Monitoring Transactions ............................11
4.2.4. Atomicity of MIDCOM Transactions ...................12
4.2.4.1. Asynchronous MIDCOM Transactions ..........12
4.2.4.2. Session Establishment and
Termination Transactions ..................12
4.2.4.3. Monitoring Transactions ...................13
4.2.4.4. Lifetime Change Transactions ..............13
4.2.4.5. Transactions Establishing New
Policy Rules ..............................14
4.2.5. Access Control .....................................14
4.3. Access Control Policies ...................................14
5. Structure of the MIB Module ....................................15
5.1. Transaction Objects .......................................16
5.1.1. midcomRuleTable ....................................17
5.1.2. midcomGroupTable ...................................19
5.2. Configuration Objects .....................................20
5.2.1. Capabilities .......................................20
5.2.2. midcomConfigFirewallTable ..........................21
5.3. Monitoring Objects ........................................22
5.3.1. midcomResourceTable ................................22
5.3.2. midcomStatistics ...................................24
5.4. Notifications .............................................25
6. Recommendations for Configuration and Operation ................26
6.1. Security Model Configuration ..............................26
6.2. VACM Configuration ........................................27
6.3. Notification Configuration ................................28
6.4. Simultaneous Access .......................................28
6.5. Avoiding Idempotency Problems .............................29
6.6. Interface Indexing Problems ...............................29
6.7. Applicability Restrictions ................................30
7. Usage Examples for MIDCOM Transactions .........................30
7.1. Session Establishment (SE) ................................31
7.2. Session Termination (ST) ..................................31
7.3. Policy Reserve Rule (PRR) .................................31
7.4. Policy Enable Rule (PER) after PRR ........................33
7.5. Policy Enable Rule (PER) without Previous PRR .............34
7.6. Policy Rule Lifetime Change (RLC) .........................35
7.7. Policy Rule List (PRL) ....................................35
7.8. Policy Rule Status (PRS) ..................................35
7.9. Asynchronous Policy Rule Event (ARE) ......................36
7.10. Group Lifetime Change (GLC) ..............................36
7.11. Group List (GL) ..........................................36
7.12. Group Status (GS) ........................................37
8. Usage Examples for Monitoring Objects ..........................37
8.1. Monitoring NAT Resources ..................................37
8.2. Monitoring Firewall Resources .............................38
9. Definitions ....................................................38
10. Security Considerations .......................................85
10.1. General Security Issues ..................................85
10.2. Unauthorized Middlebox Configuration .....................86
10.3. Unauthorized Access to Middlebox Configuration ...........87
10.4. Unauthorized Access to MIDCOM Service Configuration ......88
11. Acknowledgements ..............................................88
12. IANA Considerations ...........................................88
13. Normative References ..........................................88
14. Informative References ........................................90
1. Introduction
This memo defines a portion of the Management Information Base (MIB)
for use with network management protocols in the Internet community.
In particular, it describes a set of managed objects that allow
controlling middleboxes.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. The Internet-Standard Management Framework
For a detailed overview of the documents that describe the current
Internet-Standard Management Framework, please refer to section 7 of
RFC 3410 [RFC3410].
Managed objects are accessed via a virtual information store, termed
the Management Information Base or MIB. MIB objects are generally
accessed through the Simple Network Management Protocol (SNMP).
Objects in the MIB are defined using the mechanisms defined in the
Structure of Management Information (SMI). This memo specifies a MIB
module that is compliant to the SMIv2, which is described in STD 58,
RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580
[RFC2580].
3. Overview
The managed objects defined in this document serve for controlling
firewalls and Network Address Translators (NATs). As defined in
[RFC3234], firewalls and NATs belong to the group of middleboxes. A
middlebox is a device on the datagram path between source and
destination, which performs other functions than just IP routing. As
outlined in [RFC3303], firewalls and NATs are potential obstacles to
packet streams, for example, if dynamically negotiated UDP or TCP
port numbers are used, as in many peer-to-peer communication
applications.
As one possible solution for this problem, the IETF MIDCOM working
group defined a framework [RFC3303], requirements [RFC3304], and
protocol semantics [RFC5189] for communication between applications
and middleboxes acting as firewalls, NATs, or a combination of both.
The MIDCOM architecture and framework define a model in which trusted
third parties can be delegated to assist middleboxes in performing
their operations, without requiring application intelligence being
embedded in the middleboxes. This trusted third party is referred to
as the MIDCOM agent. The MIDCOM protocol is defined between a MIDCOM
agent and a middlebox.
The managed objects defined in this document can be used for
dynamically configuring middleboxes on the datagram path to permit
datagrams traversing the middleboxes. This way, applications can,
for example, request pinholes at firewalls and address bindings at
NATs.
Besides managed objects for controlling the middlebox operation, this
document also defines managed objects that provide information on
middlebox resource usage (such as firewall pinholes, NAT bindings,
NAT sessions, etc.) affected by requests.
Since firewalls and NATs are critical devices concerning network
security, security issues of middlebox communication need to be
considered very carefully.
3.1. Terminology
The terminology used in this document is fully aligned with the
terminology defined in [RFC5189] except for the term 'MIDCOM agent'.
For this term, there is a conflict between the MIDCOM terminology and
the SNMP terminology. The roles of entities participating in SNMP
communication are called 'manager' and 'agent' with the agent acting
as server for requests from the manager. This use of the term
'agent' is different from its use in the MIDCOM framework: The SNMP
manager corresponds to the MIDCOM agent and the SNMP agent
corresponds to the MIDCOM middlebox, also called MIDCOM server. In
order to avoid confusion in this document specifying a MIB module, we
replace the term 'MIDCOM agent' with 'MIDCOM client'. Whenever the
term 'agent' is used in this document, it refers to the SNMP agent.
Figure 1 sketches the entities of MIDCOM in relationship to SNMP
manager and SNMP agent.
+---------+ MIDCOM +-----------+
| MIDCOM |<~ ~ ~ ~ ~ ~ ~ ~>| MIDCOM |
| Client | Transaction | middlebox |
| | | (server) |
+---------+ +-----------+
^ ^
| |
v v
+---------+ +-----------+
| SNMP | SNMP | SNMP |
| Manager |<===============>| Agent |
+---------+ Protocol +-----------+
Figure 1: Mapping of MIDCOM to SNMP
4. Realizing the MIDCOM Protocol with SNMP
In order to realize middlebox communication as described in
[RFC5189], several aspects and properties of the MIDCOM protocol need
to be mapped to SNMP capabilities and expressed in terms of the
Structure of Management Information version 2 (SMIv2).
Basic concepts to be mapped are MIDCOM sessions and MIDCOM
transactions. For both, access control policies need to be
supported.
4.1. MIDCOM Sessions
SNMP has no direct support for sessions. Therefore, they need to be
modeled. A MIDCOM session is stateful and has a context that is
valid for several transactions. For SNMP, a context is valid for a
single transaction only, for example, covering just a single
request/reply pair of messages.
Properties of sessions that are utilized by the MIDCOM semantics and
not available in SNMP need to be modeled. Particularly, the
middlebox needs to be able to authenticate MIDCOM clients, authorize
access to policy rules, and send notification messages concerning
policy rules to MIDCOM clients participating in a session. In the
MIDCOM-MIB module, authentication and access control are performed on
a per-message basis using an SNMPv3 security model, such as the
User-based Security Model (USM) [RFC3414], for authentication, and
the View-based Access Control Model (VACM) [RFC3415] for access
control. Sending notifications to MIDCOM clients is controlled by
access control models such as VACM and a mostly static configuration
of objects in the SNMP-TARGET-MIB [RFC3413] and the SNMP-
NOTIFICATION-MIB [RFC3413].
This session model is static except that the MIDCOM client can switch
on and off the generation of SNMP notifications that the middlebox
sends. Recommended configurations of VACM and the SNMP-TARGET-MIB
and the SNMP-NOTIFICATION-MIB that can serve for modeling a session
are described in detail in section 6.
4.1.1. Authentication and Authorization
MIDCOM sessions are required for providing authentication,
authorization, and encryption for messages exchanged between a MIDCOM
client and a middlebox. SNMPv3 provides these features on a per-
message basis instead of a per-session basis applying a security
model and an access control model, such as USM and VACM. Per-message
security mechanisms can be considered as overhead compared to per-
session security mechanisms, but it certainly satisfies the security
requirements of middlebox communication.
For each authenticated MIDCOM client, access to the MIDCOM-MIB,
particularly to policy rules, should be configured as part of the
VACM configuration of the SNMP agent.
4.2. MIDCOM Transactions
[RFC5189] defines the MIDCOM protocol semantics in terms of
transactions and transaction parameters. Transactions are grouped
into request-reply transactions and asynchronous transactions.
SNMP offers simple transactions that in general cannot be mapped
one-to-one to MIDCOM transactions. This section describes how the
MIDCOM-MIB module implements MIDCOM transactions using SNMP
transactions. The concerned MIDCOM transactions are asynchronous
transactions and request-reply transactions. Within the set of
request-reply transactions, we distinguish configuration transactions
and monitoring transactions, because they are implemented in slightly
different ways by using SNMP transactions.
The SNMP terminology as defined in [RFC3411] does not use the concept
of transactions, but of SNMP operations. For the considerations in
this section, we use the terms SNMP GET transaction and SNMP SET
transaction. An SNMP GET transaction consists of an SNMP Read Class
operation and an SNMP Response Class operation. An SNMP SET
transaction consists of an SNMP Write Class operation and an SNMP
Response Class operation.
4.2.1. Asynchronous Transactions
Asynchronous transactions can easily be modeled by SNMP Notification
Class operations. An asynchronous transaction contains a
notification message with one to three parameters. The message can
be realized as an SNMP Notification Class operation with the
parameters implemented as managed objects contained in the
notification.
+--------------+ notification +------------+
| MIDCOM client|<--------------| middlebox |
+--------------+ message +------------+
MIDCOM asynchronous transaction
+--------------+ SNMP +------------+
| SNMP manager |<--------------| SNMP agent |
+--------------+ notification +------------+
Implementation of MIDCOM asynchronous transaction
Figure 2: MIDCOM asynchronous transaction
mapped to SNMP Notification Class operation
One of the parameters is the transaction identifier that should be
unique per middlebox. It does not have to be unique for all
notifications sent by the particular SNMP agent, but for all sent
notifications that are defined by the MIDCOM-MIB module.
Note that SNMP notifications are usually sent as unreliable UDP
packets and may be dropped before they reach their destination. If a
MIDCOM client is expecting an asynchronous notification on a specific
transaction, it would be the job of the MIDCOM client to poll the
middlebox periodically and monitor the transaction in case
notifications are lost along the way.
4.2.2. Configuration Transactions
All request-reply transactions contain a request message, a reply
message, and potentially also a set of notifications. In general,
they cannot be modeled by just having a single SNMP message per
MIDCOM message, because some of the MIDCOM messages carry a large set
of parameters that do not necessarily fit into an SNMP message
consisting of a single UDP packet only.
For configuration transactions, the MIDCOM request message can be
modeled by one or more SNMP SET transactions. The action of sending
the MIDCOM request to the middlebox is realized by writing the
parameters contained in the message to managed objects at the SNMP
agent. If necessary, the SNMP SET transaction includes creating
these managed objects. If not all parameters of the MIDCOM request
message can be set by a single SNMP SET transaction, then more than
one SET transaction is used; see Figure 3. Completion of the last of
the SNMP transactions indicates that all required parameters are set
and that processing of the MIDCOM request message can start at the
middlebox.
Please note that a single SNMP SET transaction consists of an SNMP
SET request message and an SNMP SET reply message. Both are sent as
unreliable UDP packets and may be dropped before they reach their
destination. If the SNMP SET request message or the SNMP reply
message is lost, then the SNMP manager (the MIDCOM client) needs to
take action, for example, by just repeating the SET transaction or by
first checking the success of the initial write transaction with an
SNMP GET transaction and then only repeating the SNMP SET transaction
if necessary.
+--------------+ request +------------+
| MIDCOM client|-------------->| middlebox |
+--------------+ message +------------+
MIDCOM request message
+--------------+ +------------+
| | SNMP SET | |
| |-------------->| |
| | message | |
| | | |
| | SNMP SET | |
| |<--------------| |
| | reply message | |
| SNMP manager | | SNMP agent |
| | SNMP SET | |
| |- - - - - - - >| |
| | message | |
| | | |
| | SNMP SET | |
| |< - - - - - - -| |
| | reply message | |
| | | |
| | . . . | |
+--------------+ +------------+
Implementation of MIDCOM request message
by one or more SNMP SET transactions
Figure 3: MIDCOM request message
mapped to SNMP SET transactions
The MIDCOM reply message can be modeled in two ways. The first way
is an SNMP Notification Class operation optionally followed by one or
more SNMP GET transactions as shown in Figure 4. The MIDCOM server
informs the MIDCOM client about the end of processing the request by
sending an SNMP notification. If possible, the SNMP notification
carries all reply parameters. If this is not possible, then the SNMP
manager has to perform additional SNMP GET transactions as long as
necessary to receive all of the reply parameters.
+--------------+ reply +------------+
| MIDCOM client|<--------------| middlebox |
+--------------+ message +------------+
MIDCOM reply message
+--------------+ +------------+
| | SNMP | |
| |<--------------| |
| | notification | |
| | | |
| | SNMP GET | |
| |-------------->| |
| | message | |
| SNMP manager | | SNMP agent |
| | SNMP GET | |
| |<--------------| |
| | reply message | |
| | | |
| | SNMP GET | |
| |- - - - - - - >| |
| | message | |
| | | |
| | SNMP GET | |
| |< - - - - - - -| |
| | reply message | |
| | | |
| | . . . | |
+--------------+ +------------+
Implementation of MIDCOM reply message
by an SNMP notification
and one or more SNMP GET transactions
Figure 4: MIDCOM reply message
mapped to SNMP notification and optional GET transactions
The second way replaces the SNMP Notification Class operation by a
polling operation of the SNMP manager. The manager polls status
information at the SNMP agent using SNMP GET transactions until it
detects the end of the processing of the request. Then it uses one
or more SNMP GET transactions to receive all of the reply parameters.
Note that this second way requires more SNMP operations, but is more
reliable than the first way using an SNMP Notification Class
operation.
4.2.3. Monitoring Transactions
The realization of MIDCOM monitoring transactions in terms of SNMP
transactions is simpler. The request message is very short and just
specifies a piece of information that the MIDCOM client wants to
retrieve.
+--------------+ request +------------+
| |-------------->| |
| | message | |
| MIDCOM client| | middlebox |
| | reply | |
| |<--------------| |
+--------------+ message +------------+
MIDCOM monitoring transaction
+--------------+ +------------+
| | SNMP GET | |
| |-------------->| |
| | message | |
| | | |
| | SNMP GET | |
| |<--------------| |
| | reply message | |
| SNMP manager | | SNMP agent |
| | SNMP GET | |
| |- - - - - - - >| |
| | message | |
| | | |
| | SNMP GET | |
| |< - - - - - - -| |
| | reply message | |
| | | |
| | . . . | |
+--------------+ +------------+
Implementation of MIDCOM monitoring transaction
by one or more SNMP GET messages
Figure 5: MIDCOM monitoring transaction
mapped to SNMP GET transactions
Since monitoring is a strength of SNMP, there are sufficient means to
realize MIDCOM monitoring transactions simpler than MIDCOM
configuration transactions.
All MIDCOM monitoring transactions can be realized as a sequence of
SNMP GET transactions. The number of SNMP GET transactions required
depends on the amount of information to be retrieved.
4.2.4. Atomicity of MIDCOM Transactions
Given the realizations of MIDCOM transactions by means of SNMP
transactions, atomicity of the MIDCOM transactions is not fully
guaranteed anymore. However, this section shows that atomicity
provided by the MIB module specified in section 9 is still sufficient
for meeting the MIDCOM requirements specified in [RFC3304].
4.2.4.1. Asynchronous MIDCOM Transactions
There are two asynchronous MIDCOM transactions: Asynchronous Session
Termination (AST) and Asynchronous Policy Rule Event (ARE). The very
static realization of MIDCOM sessions in the MIDCOM-MIB, as described
by section 4.1, does not anymore support the asynchronous termination
of a session. Therefore, the AST transaction is not modeled. For
the ARE, atomicity is maintained, because it is modeled by a single
atomic SNMP notification transaction.
In addition, the MIDCOM-MIB supports an Asynchronous Group Event
transaction, which is an aggregation of a set of ARE transactions.
Also, this MIDCOM transaction is implemented by a single SNMP
transaction.
4.2.4.2. Session Establishment and Termination Transactions
The MIDCOM-MIB models MIDCOM sessions in a very static way. The only
dynamic actions within these transactions are enabling and disabling
the generation of SNMP notifications at the SNMP agent.
For the Session Establishment (SE) transaction, the MIDCOM client
first reads the middlebox capabilities. It is not relevant whether
or not this action is atomic because a dynamic change of the
middlebox capabilities is not to be expected. Therefore, also non-
atomic implementations of this action are acceptable.
Then, the MIDCOM agent needs to enable the generation of SNMP
notifications at the middlebox. This can be realized by writing to a
single managed object in the SNMP-NOTIFICATION-MIB [RFC3413]. But
even other implementations are acceptable, because atomicity is not
required for this step.
For the Session Termination (ST) transaction, the only required
action is disabling the generation of SNMP notifications at the
middlebox. As for the SE transaction, this action can be realized
atomically by using the SNMP-NOTIFICATION-MIB, but also other
implementations are acceptable because atomicity is not required for
this action.
4.2.4.3. Monitoring Transactions
Potentially, the monitoring transactions Policy Rule List (PRL),
Policy Rule Status (PRS), Group List (GL), and Group Status (GS) are
not atomic, because these transactions may be implemented by more
than one SNMP GET operation.
The problem that might occur is that while the monitoring transaction
is performed, the monitored items may change. For example, while
reading a long list of policies, new policies may be added and
already read policies may be deleted. This is not in line with the
protocol semantics. However, it is not in direct conflict with the
MIDCOM requirement requesting the middlebox state to be stable and
known by the MIDCOM client, because the middlebox notifies the MIDCOM
client on all changes to its state that are performed during the
monitoring transaction by sending notifications.
If the MIDCOM client receives such a notification while performing a
monitoring transaction (or shortly after completing it), the MIDCOM
client can then either repeat the monitoring transaction or integrate
the result of the monitoring transaction with the information
received via notifications during the transaction. In both cases,
the MIDCOM client will know the state of the middlebox.
4.2.4.4. Lifetime Change Transactions
For the policy Rule Lifetime Change (RLC) transaction and the Group
Lifetime Change (GLC) transaction, atomicity is maintained. They
both have very few parameters for the request message and the reply
message. The request parameters can be transmitted by a single SNMP
SET request message, and the reply parameters can be transmitted by a
single SNMP notification message. In order to prevent idempotency
problems by retransmitting an SNMP request after a lost SNMP reply,
it is RECOMMENDED that either snmpSetSerialNo (see [RFC3418]) is
included in the corresponding SNMP SET request or the value of the
SNMP retransmission timer be lower than the smallest requested
lifetime value. The same recommendation applies to the smallest
requested value for the midcomRuleStorageTime. MIDCOM client
implementations MAY completely avoid this problem by configuring
their SNMP stack such that no retransmissions are sent.
4.2.4.5. Transactions Establishing New Policy Rules
Analogous to the monitoring transactions, the atomicity may not be
given for Policy Reserve Rule (PRR) and Policy Enable Rule (PER)
transactions. Both transactions are potentially implemented using
more than one SNMP SET operation and GET operation for obtaining
transaction reply parameters. The solution for this loss of
atomicity is the same as for the monitoring transactions.
There is an additional atomicity problem for PRR and PER. If
transferring request parameters requires more than a single SET
operation, then there is the potential problem that multiple MIDCOM
clients sharing the same permissions are able to access the same
policy rule. In this case, a client could alter request parameters
already set by another client before the first client could complete
the request. However, this is acceptable since usually only one
agent is creating a policy rule and filling it subsequently. It can
also be assumed that in most cases where clients share permissions,
they act in a more or less coordinated way avoiding such
interferences.
All atomicity problems caused by using multiple SNMP SET transactions
for implementing the MIDCOM request message can be avoided by
transferring all request parameters with a single SNMP SET
transaction.
4.2.5. Access Control
Since SNMP does not offer per-session authentication and
authorization, authentication and authorization are performed per
SNMP message sent from the MIDCOM client to the middlebox.
For each transaction, the MIDCOM client has to authenticate itself as
an authenticated principal, such as a USM user. Then, the
principal's access rights to all resources affected by the
transaction are checked. Access right control is realized by
configuring the access control mechanisms, such as VACM, at the SNMP
agent.
4.3. Access Control Policies
Potentially, a middlebox has to control access for a large set of
MIDCOM clients and to a large set of policy rules configuring
firewall pinholes and NAT bindings. Therefore, it can be beneficial
to use access control policies for specifying access control rules.
Generating, provisioning, and managing these policies are out of
scope of this MIB module.
However, if such an access control policy system is used, then the
SNMP agent acts as a policy enforcement point. An access control
policy system must transform all active policies into configurations
of, for example, the SNMP agent's View-based Access Control Model
(VACM).
The mechanisms of access control models, such as VACM, allow an
access control policy system to enforce MIDCOM client authentication
rules and general access control of MIDCOM clients to middlebox
control.
The mechanisms of VACM can be used to enforce access control of
authenticated clients to MIDCOM-MIB policy rules based on the concept
of ownership. For example, an access control policy can specify that
MIDCOM-MIB policy rules owned by user A cannot be accessed at all by
user B, can be read by user C, and can be read and modified by user
D.
Further access control policies can control access to concrete
middlebox resources. These are enforced, when a MIDCOM request is
processed. For example, an authenticated MIDCOM client may be
authorized to request new MIDCOM policies to be established, but only
for certain IP address ranges. The enforcement of this kind of
policies may not be realizable using available SNMP mechanisms, but
needs to be performed by the individual MIB module implementation.
5. Structure of the MIB Module
The MIB module defined in section 9 contains three kinds of managed
objects:
- Transaction objects
Transaction objects are required for implementing the MIDCOM
protocol requirements defined in [RFC3304] and the MIDCOM
protocol semantics defined in [RFC5189].
- Configuration objects
Configuration objects can be used for retrieving middlebox
capability information (mandatory) and for setting parameters of
the implementation of transaction objects (optional).
- Monitoring objects
The optional monitoring objects provide information about used
resources and about MIDCOM transaction statistics.
The transaction objects are organized in two tables: the
midcomRuleTable and the midcomGroupTable. Entity relationships of
entries of these tables and the midcomResourceTable from the
monitoring objects are illustrated by Figure 6.
+--------------------+
| midcomRuleEntry |
| indexed by |
| midcomRuleOwner |
| midcomGroupIndex |
| midcomRuleIndex |
+--------------------+
1...n | | 1
| |
1 | | 1
+--------------------+ +---------------------+
| midcomGroupEntry | | midcomResourceEntry |
| indexed by | | indexed by |
| midcomRuleOwner | | midcomRuleOwner |
| midcomGroupIndex | | midcomGroupIndex |
+--------------------+ | midcomRuleIndex |
+---------------------+
| | |
| | |
v v v
NAT Firewall other
MIB MIB MIB
Figure 6: Entity relationships of table entries
A MIDCOM client can create and delete entries in the midcomRuleTable.
Entries in the midcomGroupTable are generated automatically as soon
as there is an entry in the midcomRuleTable using the
midcomGroupIndex. The midcomGroupTable can be used as shortcut for
accessing all member rules with a single transaction. MIDCOM clients
can group policy rules for various purposes. For example, they can
assign a unique value for the midcomGroupIndex to all rules belonging
to a single application or an application session served by the
MIDCOM agent.
The midcomResourceTable augments the midcomRuleTable by information
on the relationship of entries of the midcomRuleTable to resources
listed in other MIB modules, such as the NAT-MIB [RFC4008].
5.1. Transaction Objects
The transaction objects are structured according to the MIDCOM
semantics described in [RFC5189] into two subtrees, one for policy
rule control and one for policy rule group control.
5.1.1. midcomRuleTable
The midcomRuleTable contains information about policy rules including
policy rules to be established, policy rules for which establishing
failed, established policy rules, and terminated policy rules.
Entries in this table are indexed by the combination of
midcomRuleOwner, midcomGroupIndex, and midcomRuleIndex. The
midcomRuleOwner is the owner of the rule; the midcomGroupIndex is the
index of the group of which the policy rule is a member.
midcomRuleOwner is of type SnmpAdminString, a textual convention that
allows for use of the SNMPv3 View-based Access Control Model (VACM
[RFC3415]) and allows a management application to identify its
entries.
Entries in this table are created by writing to midcomRuleRowStatus.
Entries are removed when both their midcomRuleLifetime and
midcomRuleStorageTime are timed out by counting down to 0. A MIDCOM
client can explicitly remove an entry by setting midcomRuleLifetime
and midcomRuleStorageTime to 0.
The table contains the following columnar objects:
o midcomRuleIndex
The index of this entry must be unique in combination with the
midcomRuleOwner and the midcomGroupIndex of the entry.
o midcomRuleAdminStatus
For establishing a new policy rule, a set of objects in this
entry needs to be written first. These objects are the request
parameters. Then, by writing either reserve(1) or enable(2) to
this object, the MIDCOM-MIB implementation is triggered to start
processing the parameters and tries to establish the specified
policy rule.
o midcomRuleOperStatus
This read-only object indicates the current status of the entry.
The entry may have an initializing state, it may have a transient
state while processing requests, it may have an error state after
a request was rejected, it may have a state where a policy rule
is established, or it may have a terminated state.
o midcomRuleStorageType
This object indicates whether or not the policy rule is stored as
volatile, non-volatile, or permanent. Depending on the MIDCOM-
MIB implementation, this object may be writable.
o midcomRuleStorageTime
This object indicates how long the entry will still exist after
entering an error state or a termination state.
o midcomRuleError
This object is a string indicating the reason for entering an
error state.
o midcomRuleInterface
This object indicates the IP interface for which enforcement of a
policy rule is requested or performed, respectively.
o midcomRuleFlowDirection
This object indicates a flow direction for which a policy enable
rule was requested or established, respectively.
o midcomRuleMaxIdleTime
This object indicates the maximum idle time of the policy rule in
seconds. If no packet to which the policy rule applies passes
the middlebox for the time specified by midcomRuleMaxIdleTime,
then the policy rule enters a termination state.
o midcomRuleTransportProtocol
This object indicates a transport protocol for which a policy
reserve rule or policy enable rule was requested or established,
respectively.
o midcomRulePortRange
This object indicates a port range for which a policy reserve
rule or policy enable rule was requested or established,
respectively.
o midcomRuleLifetime
This object indicates the remaining lifetime of an established
policy rule. The MIDCOM client can change the remaining lifetime
by writing to it.
Beyond the listed objects, the table contains 10 further objects
describing address parameters. They include the IP version, IP
address, prefix length and port number for the internal address (A0),
inside address (A1), outside address (A2), and external address (A3).
These objects serve as parameters specifying a request or an
established policy, respectively.
A0, A1, A2, and A3 are address tuples defined according to the MIDCOM
semantics [RFC5189]. Each of them identifies either a communication
endpoint at an internal or external device or an allocated address at
the middlebox.
+----------+ +----------+
| internal | A0 A1 +-----------+ A2 A3 | external |
| endpoint +----------+ middlebox +----------+ endpoint |
+----------+ +-----------+ +----------+
Figure 7: Address tuples A0 - A3
- A0 - internal endpoint: Address tuple A0 specifies a communication
endpoint of a device within the internal network, with respect to
the middlebox.
- A1 - middlebox inside address: Address tuple A1 specifies a
virtual communication endpoint at the middlebox within the
internal network. A1 is the destination address for packets
passing from the internal endpoint to the middlebox and is the
source for packets passing from the middlebox to the internal
endpoint.
- A2 - middlebox outside address: Address tuple A2 specifies a
virtual communication endpoint at the middlebox within the
external network. A2 is the destination address for packets
passing from the external endpoint to the middlebox and is the
source for packets passing from the middlebox to the external
endpoint.
- A3 - external endpoint: Address tuple A3 specifies a communication
endpoint of a device within the external network, with respect to
the middlebox.
The MIDCOM-MIB requires the MIDCOM client to specify address tuples
A0 and A3. This might be a problem for applications that are not
designed in a firewall-friendly way. An example is an FTP
application that uses the PORT command (instead of the recommended
PASV command). The problem only occurs when the middlebox offers
twice-NAT functionality, and it can be fixed following
recommendations for firewall-friendly communication.
5.1.2. midcomGroupTable
The midcomGroupTable has an entry per existing policy rule group.
Entries in this table are created automatically when creating member
entries in the midcomRuleTable. Entries are automatically removed
from this table when the last member entry is removed from the
midcomRuleTable. Entries cannot be created or removed explicitly by
the MIDCOM client.
Entries are indexed by the midcomRuleOwner of the rules that belong
to the group and by a specific midcomGroupIndex. This allows each
midcomRuleOwner to maintain its own independent group namespace.
An entry of the table contains the following objects:
o midcomGroupIndex
The index of this entry must be unique in combination with the
midcomRuleOwner of the entry.
o midcomGroupLifetime
This object indicates the maximum of the remaining lifetimes of
all established policy rules that are members of the group. The
MIDCOM client can change the remaining lifetime of all member
policies by writing to this object.
5.2. Configuration Objects
The configuration subtree contains middlebox capability and
configuration information. Some of the contained objects are
(optionally) writable and can also be used for configuring the
middlebox service.
The capabilities subtree contains some general capability information
and detailed information per supported IP interface. The
midcomConfigFirewallTable can be used to configure how the MIDCOM-MIB
implementation creates firewall rules in its firewall modules.
Note that typically, configuration objects are not intended to be
written by MIDCOM clients. In general, write access to these objects
needs to be restricted more strictly than write access to transaction
objects.
5.2.1. Capabilities
Information on middlebox capabilities, i.e., capabilities of the
MIDCOM-MIB implementation, is provided by the midcomCapabilities
subtree of managed objects. The following objects are defined:
o midcomConfigMaxLifetime
This object indicates the maximum lifetime that this middlebox
allows policy rules to have.
o midcomConfigPersistentRules
This is a boolean object indicating whether or not the middlebox
is capable of storing policy rules persistently.
Further capabilities are provided by the midcomConfigIfTable per
IP interface. This table contains just two objects. The first
one is a BITS object called midcomConfigIfBits containing the
following bit values:
o ipv4 and ipv6
These two bit values provide information on which IP versions are
supported by the middlebox at the indexed interface.
o addressWildcards and portWildcards
These two bit values provide information on wildcarding supported
by the middlebox at the indexed interface.
o firewall and nat
These two bit values provide information on availability of
firewall and NAT functionality at the indexed interface.
o portTranslation, protocolTranslation, and twiceNat
These three bit values provide information on the kind of NAT
functionality available at the indexed interface.
o inside
This bit indicates whether or not the indexed interface is an
inside interface with respect to NAT functionality.
The second object, called midcomConfigIfEnabled, indicates whether
the middlebox capabilities described by midcomConfigIfBits are
available or not available at the indexed IP interface.
The midcomConfigIfTable uses index 0 for indicating capabilities that
are available for all interfaces.
5.2.2. midcomConfigFirewallTable
The midcomConfigFirewallTable serves for configuring how policy rules
created by MIDCOM clients are realized as firewall rules of a
firewall implementation. Particularly, the priority used for
MIDCOM-MIB policy rules can be configured. For a single firewall
implementation at a particular IP interface, all MIDCOM-MIB policy
rules are realized as firewall rules with the same priority. Also, a
firewall rule group name can be configured. The table is indexed by
the IP interface index.
An entry of the table contains the following objects:
o midcomConfigFirewallGroupId
This object indicates the firewall rule group to which all
firewall rules of the MIDCOM server are assigned.
o midcomConfigFirewallPriority
This object indicates the priority assigned to all firewall rules
of the MIDCOM server.
5.3. Monitoring Objects
The monitoring objects are structured into two subtrees: the resource
subtree and the statistics subtree. The resource subtree provides
information about which resources are used by which policy rule. The
statistics subtree provides statistics about the usage of transaction
objects.
5.3.1. midcomResourceTable
Information about resource usage per policy rule is provided by the
midcomResourceTable. Each entry in the midcomResourceTable describes
resource usage of exactly one policy rule.
Resources are NAT resources and firewall resources, depending on the
type of middlebox. Used NAT resources include NAT bindings and NAT
sessions. NAT address mappings are not covered. For firewalls,
firewall filter rules are considered as resources.
The values provided by the following objects on NAT binds and NAT
sessions may refer to the detailed resource usage description in the
NAT-MIB module [RFC4008].
The values provided by the following objects on firewall rules may
refer to more detailed firewall resource usage descriptions in other
MIB modules.
Entries in the midcomResourceTable are only valid if the
midcomRuleOperStatus object of the corresponding entry in the
midcomRuleTable has a value of either reserved(7) or enabled(8).
An entry of the table contains the following objects:
o midcomRscNatInternalAddrBindMode
This object indicates whether the binding of the internal address
is an address NAT binding or an address-port NAT binding.
o midcomRscNatInternalAddrBindId
This object identifies the NAT binding for the internal address
in the NAT engine.
o midcomRscNatExternalAddrBindMode
This object indicates whether the binding of the external address
is an address NAT binding or an address-port NAT binding.
o midcomRscNatExternalAddrBindId
This object identifies the NAT binding for the external address
in the NAT engine.
o midcomRscNatSessionId1
This object links to the first NAT session associated with one of
the above NAT bindings.
o midcomRscNatSessionId2
This object links to the optional second NAT session associated
with one of the above NAT bindings.
o midcomRscFirewallRuleId
This object indicates the firewall rule for this policy rule.
The MIDCOM-MIB module does not require a middlebox to implement
further specific middlebox (NAT, firewall, etc.) MIB modules as, for
example, the NAT-MIB module [RFC4008].
The resource identifiers in the midcomResourceTable may be vendor
proprietary in the cases where the middlebox does not implement the
NAT-MIB [RFC4008] or a firewall MIB. The MIDCOM-MIB module affects
NAT binding and sessions, as well as firewall pinholes. It is
intentionally not specified in the MIDCOM-MIB module how these NAT
and firewall resources are allocated and managed, since this depends
on the MIDCOM-MIB implementation and middlebox's capabilities.
However, the midcomResourceTable is useful for understanding which
resources are affected by which MIDCOM-MIB transaction.
The midcomResourceTable is beneficial to the middlebox administrator
in that the table lists all MIDCOM transactions and the middlebox
specific resources to which these transactions refer. For instance,
multiple MIDCOM clients might end up using the same NAT bind, yet
each MIDCOM client might define a Lifetime parameter and
directionality for the bind that is specific to the transaction.
MIDCOM-MIB implementations are responsible for impacting underlying
middlebox resources so as to satisfy the sometimes overlapping
requirements on the same resource from multiple MIDCOM clients.
Managing these resources is not a trivial task for MIDCOM-MIB
implementers. It is possible that different MIDCOM-MIB policy rules
owned by different MIDCOM clients share a NAT binding or a firewall
rule. Then common properties, for example, the lifetime of the
resource, need to be managed such that all clients are served well
and changes to these resources need to be communicated to all
affected clients. Also, dependencies between resources, for example,
the precedence order of firewall rules, need to be considered
carefully in order to avoid that different policy rules --
potentially owned by different clients -- influence each other.
MIDCOM clients may use the midcomResourceTable of the MIDCOM-MIB
module in conjunction with the NAT-MIB module [RFC4008] to determine
which resources of the NAT are used for MIDCOM. The NAT-MIB module
stores the configured NAT bindings and sessions, and MIDCOM clients
can use the information of the midcomResourceTable to sort out those
NAT resources that are used by the MIDCOM-MIB module.
5.3.2. midcomStatistics
The statistics subtree contains a set of non-columnar objects that
provide 'MIDCOM protocol statistics', i.e., statistics about the
usage of transaction objects.
o midcomCurrentOwners
This object indicates the number of different values for
midcomRuleOwner for all current entries in the midcomRuleTable.
o midcomOwnersTotal
This object indicates the summarized number of all different
values that occurred for midcomRuleOwner in the midcomRuleTable
current and in the past.
o midcomTotalRejectedRuleEntries
This object indicates the total number of failed attempts to
create an entry in the midcomRuleTable.
o midcomCurrentRulesIncomplete
This object indicates the total number of policy rules that have
not been fully loaded into a table row of the midcomRuleTable.
o midcomTotalIncorrectReserveRules
This object indicates the total number of policy reserve rules
that were rejected because the request was incorrect.
o midcomTotalRejectedReserveRules
This object indicates the total number of policy reserve rules
that were failed while being processed.
o midcomCurrentActiveReserveRules
This object indicates the number of currently active policy
reserve rules in the midcomRuleTable.
o midcomTotalExpiredReserveRules
This object indicates the total number of expired policy reserve
rules.
o midcomTotalTerminatedOnRqReserveRules
This object indicates the total number of policy reserve rules
that were terminated on request.
o midcomTotalTerminatedReserveRules
This object indicates the total number of policy reserve rules
that were terminated, but not on request.
o midcomTotalIncorrectEnableRules
This object indicates the total number of policy enable rules
that were rejected because the request was incorrect.
o midcomTotalRejectedEnableRules
This object indicates the total number of policy enable rules
that were failed while being processed.
o midcomCurrentActiveEnableRules
This object indicates the number of currently active policy
enable rules in the midcomRuleTable.
o midcomTotalExpiredEnableRules
This object indicates the total number of expired policy enable
rules.
o midcomTotalTerminatedOnRqEnableRules
This object indicates the total number of policy enable rules
that were terminated on request.
o midcomTotalTerminatedEnableRules
This object indicates the total number of policy enable rules
that were terminated, but not on request.
5.4. Notifications
For informing MIDCOM clients about state changes of MIDCOM-MIB
implementations, three notifications can be used. They notify the
MIDCOM client about state changes of individual policy rules or of
groups of policy rules. Different notifications are used for
different kinds of transactions.
For asynchronous transactions, unsolicited notifications are used.
The only asynchronous transaction that needs to be modeled by the
MIDCOM-MIB is the Asynchronous Policy Rule Event (ARE). The ARE may
be caused by the expiration of a policy rule lifetime, the expiration
of the idle time, or an internal change in policy rule lifetime by
the MIDCOM-MIB implementation for whatever reason.
For configuration transactions, solicited notifications are used.
This concerns the Policy Reserve Rule (PRR) transaction, the Policy
Enable Rule (PER) transaction, the Policy Rule Lifetime Change (RLC)
transaction, and the Group Lifetime Change (GLC) transaction.
The separation between unsolicited and solicited notifications gives
the implementer of a MIDCOM client some freedom to make design
decisions on how to model the MIDCOM reply message as described at
the end of section 4.2.2. Depending on the choice, processing of
solicited notifications may not be required. In such a case,
delivery of solicited notification may be disabled, for example, by
an appropriate configuration of the snmpNotifyFilterTable such that
solicited notifications are filtered differently to unsolicited
notifications.
o midcomUnsolicitedRuleEvent
This notification can be generated for indicating the change of a
policy rule's state or lifetime. It is used for performing the
ARE transaction.
o midcomSolicitedRuleEvent
This notification can be generated for indicating the requested
change of a policy rule's state or lifetime. It is used for
performing PRR, PER, and RLC transactions.
o midcomSolicitedGroupEvent
This notification can be generated for indicating the requested
change of a policy rule group's lifetime. It is used for
performing the GLC transaction.
6. Recommendations for Configuration and Operation
Configuring MIDCOM-MIB security is highly sensitive for obvious
reasons. This section gives recommendations for securely configuring
the SNMP agent acting as MIDCOM server. In addition, recommendations
for avoiding idempotency problems are given and restrictions of
MIDCOM-MIB applicability to a special set of applications are
discussed.
6.1. Security Model Configuration
Since controlling firewalls and NATs is highly sensitive, it is
RECOMMENDED that SNMP Command Responders implementing the MIDCOM-MIB
module use the authPriv security level for all users that may access
managed objects of the MIDCOM-MIB module.
6.2. VACM Configuration
Entries in the midcomRuleTable and the midcomGroupTable provide
information about existing firewall pinholes and/or NAT sessions.
They also could be used for manipulating firewall pinholes and/or NAT
sessions. Therefore, access control to these objects is essential
and should be restrictive.
It is RECOMMENDED that SNMP Command Responders instantiating an
implementation of the MIDCOM-MIB module use VACM for controlling
access to managed objects in the midcomRuleTable and the
midcomGroupTable.
It is further RECOMMENDED that individual MIDCOM clients, acting as
SNMP Command Generators, only have access to an entry in the
midcomRuleTable, the midcomResourceTable, or the midcomGroupTable, if
they created the entry directly in the midcomRuleTable or indirectly
in the midcomGroupTable and midcomResourceTable. Exceptions to this
recommendation are situations where access by multiple MIDCOM clients
to managed objects is explicitly required. One example is fail-over
for MIDCOM agents where the stand-by MIDCOM agent needs the same
access rights to managed objects as the currently active MIDCOM
agent. Another example is a supervisor MIDCOM agent that monitors
activities of other MIDCOM agents and/or may be used by network
management systems to modify entries in tables of the MIDCOM-MIB.
For this reason, all three tables listed above have the
midcomRuleOwner as initial index. It is RECOMMENDED that MIDCOM
clients acting as SNMP Command Generator have access to the
midcomRuleTable and the midcomGroupTable restricted to entries with
the initial index matching either their SNMP securityName or their
VACM groupName. It is RECOMMENDED that they do not have access to
entries in these tables with initial indices other than their SNMP
securityName or their VACM groupName. It is RECOMMENDED that this
VACM configuration is applied to read access, write access, and
notify access for all objects in the midcomRuleTable and the
midcomGroupTable.
Note that less restrictive access rights MAY be granted to other
users, for example, to a network management application, that
monitors MIDCOM policy rules.
6.3. Notification Configuration
For each MIDCOM client that has access to the midcomRuleTable, a
notification target SHOULD be configured at a Command Responder
instantiating an implementation of the MIDCOM-MIB. It is RECOMMENDED
that such a configuration be retrievable from the Command Responder
via the SNMP-TARGET-MIB [RFC3413].
For each entry of the snmpTargetAddrTable that is related to a MIDCOM
client, there SHOULD be an individual corresponding entry in the
snmpTargetParamsTable.
An implementation of the MIDCOM-MIB SHOULD also implement the SNMP-
NOTIFICATION-MIB [RFC3413]. An instance of an implementation of the
MIDCOM-MIB SHOULD have an individual entry in the
snmpNotifyFilterProfileTable for each MIDCOM client that has access
to the midcomRuleTable.
An instance of an implementation of the MIDCOM-MIB SHOULD allow
MIDCOM clients to start and stop the generation of notifications
targeted at themselves. This SHOULD be realized by giving the MIDCOM
clients write access to the snmpNotifyFilterTable. If appropriate
entries of the snmpNotifyFilterTable are established in advance, then
this can be achieved by granting MIDCOM clients write access only to
the columnar object snmpNotifyFilterType.
It is RECOMMENDED that VACM be configured such that each MIDCOM agent
can only access entries in the snmpTargetAddrTable, the
snmpTargetParamsTable, the snmpNotifyFilterProfileTable, and the
snmpFilterTable that concern that particular MIDCOM agent.
Typically, read access to the snmpTargetAddrTable, the
snmpTargetParamsTable, and the snmpNotifyFilterProfileTable is
sufficient. Write access may be required for objects of the
snmpFilterTable.
6.4. Simultaneous Access
Situations with two MIDCOM clients simultaneously modifying the same
policy rule should be avoided. For each entry in the
midcomRuleTable, there should be only one client at a time that
modifies it. If two MIDCOM clients share the same midcomRuleOwner
index of the midcomRuleTable, then conflicts can be avoided, for
example, by
- scheduling access times, as, for example, in the fail-over case;
- using different midcomGroupIndex values per client; or
- using non-overlapping intervals for values of the
midcomRuleIndex per client.
6.5. Avoiding Idempotency Problems
As already discussed in section 4.2.4.4, the following recommendation
is given for avoiding idempotency problems.
In general, idempotency problems can be solved by including
snmpSetSerialNo (see [RFC3418]) in SNMP SET requests.
In case this feature is not used, it is RECOMMENDED that the value of
the SNMP retransmission timer of a MIDCOM client (acting as SNMP
Command Generator) is lower than the smallest requested value for any
rule lifetime or rule idle time in order to prevent idempotency
problems with setting midcomRuleLifetime and midcomRuleMaxIdleTime
when retransmitting an SNMP SET request after a lost SNMP reply.
MIDCOM client implementations MAY completely avoid this problem by
configuring their SNMP stack such that no retransmissions are sent.
Similar considerations apply to MIDCOM-MIB implementations acting as
Notification Originator when sending a notification
(midcomUnsolicitedRuleEvent, midcomSolicitedRuleEvent or
midcomSolicitedGroupEvent) containing the remaining lifetime of a
policy rule or a policy rule group, respectively.
6.6. Interface Indexing Problems
A well-known problem of MIB modules is indexing IP interfaces after a
re-initialization of the managed device. The index for interfaces
provided by the ifTable (see IF-MIB in [RFC2863]) may change during
re-initialization, for example, when physical interfaces are added or
removed.
The MIDCOM-MIB module uses the interface index for indicating at
which interface which policy rule is (or is to be) applied. Also,
this index is used for indicating how policy rules are prioritized at
certain interfaces. The MIDCOM-MIB module specification requires
that information provided is always correct. This implies that after
re-initialization, interface index values of policy rules or firewall
configurations may have changed even though they still refer to the
same interface as before the re-initialization.
MIDCOM client implementations need to be aware of this potential
behavior. It is RECOMMENDED that before writing the value or using
the value of indices that depend on the ifTable the MIDCOM client
checks if the middlebox has been re-initialized recently.
MIDCOM-MIB module implementations MUST track interface changes of IP
interface indices in the ifTable. This implies that after a re-
initialization of a middlebox, a MIDCOM-MIB implementation MUST make
sure that each instance of an interface index in the MIDCOM-MIB
tables still points to the same interface as before the re-
initialization. For any instance for which this is not possible, all
affected entries in tables of the MIDCOM-MIB module MUST be either
terminated, disabled, or deleted, as specified in the DESCRIPTION
clause of the respective object. This concerns all objects in the
MIDCOM-MIB module that are of type InterfaceIndexOrZero.
6.7. Applicability Restrictions
As already discussed in section 5.1.1, the MIDCOM-MIB requires the
MIDCOM client to specify address tuples A0 and A3. This can be a
problem for applications that do not have this information available
when they need to configure the middlebox. For some applications,
there are usage scenarios where address information is only available
for a single address realm, A0 and A1 in the private realm or A2 and
A3 in the public realm. An example is an FTP application using the
PORT command (instead of the PASV command). The problem occurs when
the middlebox offers twice-NAT functionality.
7. Usage Examples for MIDCOM Transactions
This section presents some examples that explain how a MIDCOM client
acting as SNMP manager can use the MIDCOM-MIB module defined in this
memo. The purpose of these examples is to explain the steps that are
required to perform MIDCOM transactions. For each MIDCOM transaction
defined in the MIDCOM semantics [RFC5189], a sequence of SNMP
operations that realizes the transaction is described.
The examples described below are recommended procedures for MIDCOM
clients. Clients may choose to operate differently.
For example, they may choose not to receive solicited notifications
on completion of a transaction, but to poll the MIDCOM-MIB instead
until the transaction is completed. This can be achieved by
performing step 2 of the SE transaction (see below) differently. The
MIDCOM agent then creates an entry in the snmpNotifyFilterTable such
that only the midcomUnsolicitedRuleEvent may pass the filter and is
sent to the MIDCOM client. In this case, the PER, PRR, and RLC
transactions require a polling loop wherever in the example below the
MIDCOM client waits for a notification.
7.1. Session Establishment (SE)
The MIDCOM-MIB realizes most properties of MIDCOM sessions in a very
static way. Only the generation of notifications targeted at the
MIDCOM client is enabled by the client for session establishment.
1. The MIDCOM client checks the middlebox capabilities by reading
objects in the midcomCapabilitiesGroup.
2. The MIDCOM client enables generation of notifications on events
concerning the policy rules controlled by the client. If the
SNMP-NOTIFICATION-MIB is supported as recommended by section 6.3
of this document, then the agent just has to change the value of a
object snmpNotifyFilterType in the corresponding entry of the
snmpNotifyFilterTable from included(1) to excluded(2).
7.2. Session Termination (ST)
For terminating a session, the MIDCOM client just disables the
generation of notifications for this client.
1. The MIDCOM client disables generation of notifications on events
concerning the policy rules controlled by the client. If the
SNMP-NOTIFICATION-MIB is supported as recommended by section 6.3
of this document, then the agent just has to change the value of a
object snmpNotifyFilterType in the corresponding entry of the
snmpNotifyFilterTable from included(1) to excluded(2).
7.3. Policy Reserve Rule (PRR)
This example explains steps that may be performed by a MIDCOM client
to establish a policy reserve rule.
1. The MIDCOM client creates a new entry in the midcomRuleTable by
writing to midcomRuleRowStatus. The chosen value for index object
midcomGroupIndex determines the group membership of the created
rule. Note that choosing an unused value for midcomGroupIndex
creates a new entry in the midcomGroupTable.
2. The MIDCOM client sets the following objects in the new entry of
the midcomRuleTable to specify all request parameters of the PRR
transaction:
- midcomRuleMaxIdleTime
- midcomRuleInterface
- midcomRuleTransportProtocol
- midcomRulePortRange
- midcomRuleInternalIpVersion
- midcomRuleExternalIpVersion
- midcomRuleInternalIpAddr
- midcomRuleInternalIpPrefixLength
- midcomRuleInternalPort
- midcomRuleLifetime
Note that several of these parameters have default values that can
be used.
3. The MIDCOM client sets the midcomRuleAdminStatus objects in the
new row of the midcomRuleTable to reserve(1).
4. The MIDCOM client awaits a midcomSolicitedRuleEvent notification
concerning the new policy rule in the midcomRuleTable. Waiting
for the notification is timed out after a pre-selected maximum
waiting time. In case of a timeout while waiting for the
notification or if the client does not use notifications, the
MIDCOM client retrieves the status of the midcomRuleEntry by one
or more SNMP GET operations.
5. After receiving the midcomSolicitedRuleEvent notification, the
MIDCOM client checks the lifetime value carried by the
notification. If it is greater than 0, the MIDCOM client reads
all positive reply parameters of the PRR transaction:
- midcomRuleOutsideIpAddr
- midcomRuleOutsidePort
- midcomRuleMaxIdleTime
- midcomRuleLifetime
If the lifetime equals 0, then the MIDCOM client reads the
midcomRuleOperStatus and the midcomRuleError in order to analyze
the failure reason.
6. Optionally, after receiving the midcomSolicitedRuleEvent
notification with a lifetime value greater than 0, the MIDCOM
client may check the midcomResourceTable for the middlebox
resources allocated for this policy reserve rule. Note that PRR
does not necessarily allocate any middlebox resource visible in
the NAT-MIB module or in a firewall MIB module, since it does a
reservation only. If, however, the PRR overlaps with already
existing PERs, then the PRR may be related to middlebox resources
visible in other MIB modules.
7.4. Policy Enable Rule (PER) after PRR
This example explains steps that may be performed by a MIDCOM client
to establish a policy enable rule after a corresponding policy
reserve rule was already established.
1. The MIDCOM client sets the following objects in the row of the
established PRR in the midcomRuleTable to specify all request
parameters of the PER transaction:
- midcomRuleMaxIdleTime
- midcomRuleExternalIpAddr
- midcomRuleExternalIpPrefixLength
- midcomRuleExternalPort
- midcomRuleFlowDirection
Note that several of these parameters have default values that can
be used.
2. The MIDCOM client sets the midcomRuleAdminStatus objects in the
row of the established PRR in the midcomRuleTable to enable(1).
3. The MIDCOM client awaits a midcomSolicitedRuleEvent notification
concerning the new row in the midcomRuleTable. Waiting for the
notification is timed out after a pre-selected maximum waiting
time. In case of a timeout while waiting for the notification or
if the client does not use notifications, the MIDCOM client
retrieves the status of the midcomRuleEntry by one or more SNMP
GET operations.
4. After receiving the midcomSolicitedRuleEvent notification, the
MIDCOM client checks the lifetime value carried by the
notification. If it is greater than 0, the MIDCOM client reads
all positive reply parameters of the PER transaction:
- midcomRuleInsideIpAddr
- midcomRuleInsidePort
- midcomRuleMaxIdleTime
If the lifetime equals 0, then the MIDCOM client reads the
midcomRuleOperStatus and the midcomRuleError in order to analyze
the failure reason.
5. Optionally, after receiving the midcomSolicitedRuleEvent
notification with a lifetime value greater than 0, the MIDCOM
client may check the midcomResourceTable for the allocated
middlebox resources for this policy enable rule.
7.5. Policy Enable Rule (PER) without Previous PRR
This example explains steps that may be performed by a MIDCOM client
to establish a policy enable rule for which no PRR transaction has
been performed before.
1. Identical to step 1 for PRR (section 7.3).
2. Identical to step 2 for PRR (section 7.3).
3. The MIDCOM client sets the following objects in the new row of the
midcomRuleTable to specify all request parameters of the PER
transaction:
- midcomRuleInterface
- midcomRuleFlowDirection
- midcomRuleTransportProtocol
- midcomRulePortRange
- midcomRuleInternalIpVersion
- midcomRuleExternalIpVersion
- midcomRuleInternalIpAddr
- midcomRuleInternalIpPrefixLength
- midcomRuleInternalPort
- midcomRuleExternalIpAddr
- midcomRuleExternalIpPrefixLength
- midcomRuleExternalPort
- midcomRuleLifetime
Note that several of these parameters have default values that can
be used.
4. The MIDCOM client sets the midcomRuleAdminStatus objects in the
new row of the midcomRuleTable to enable(1).
5. Identical to step 4 for PRR (section 7.3).
6. After receiving the midcomSolicitedRuleEvent notification, the
MIDCOM client checks the lifetime value carried by the
notification. If it is greater than 0, the MIDCOM client reads
all positive reply parameters of the PRR transaction:
- midcomRuleInsideIpAddr
- midcomRuleInsidePort
- midcomRuleOutsideIpAddr
- midcomRuleOutsidePort
- midcomRuleMaxIdleTime
If the lifetime equals 0, then the MIDCOM client reads the
midcomRuleOperStatus and the midcomRuleError in order to analyze
the failure reason.
7. Optionally, after receiving the midcomSolicitedRuleEvent
notification with a lifetime value greater than 0, the MIDCOM
client may check the midcomResourceTable for the allocated
middlebox resources for this policy enable rule.
7.6. Policy Rule Lifetime Change (RLC)
This example explains steps that may be performed by a MIDCOM client
to change the lifetime of a policy rule. Changing the lifetime to 0
implies terminating the policy rule.
1. The MIDCOM client issues a SET request for writing the desired
lifetime to the midcomRuleLifetime object in the corresponding row of
the midcomRuleTable. This does not have any effect if the lifetime
is already expired.
2. The MIDCOM client awaits a midcomSolicitedRuleEvent notification
concerning the corresponding row in the midcomRuleTable. Waiting for
the notification is timed out after a pre-selected maximum waiting
time. In case of a timeout while waiting for the notification or if
the client does not use notifications, the MIDCOM client retrieves
the status of the midcomRuleEntry by one or more SNMP GET operations.
3. After receiving the midcomSolicitedRuleEvent notification MIDCOM
client checks the lifetime value carried by the notification.
7.7. Policy Rule List (PRL)
The SNMP agent can browse the list of policy rules by browsing the
midcomRuleTable. For each observed row in this table, the SNMP agent
should check the midcomRuleOperStatus in order to find out if the row
contains information about an established policy rule or of a rule
that is under construction or already terminated.
7.8. Policy Rule Status (PRS)
The SNMP agent can retrieve all status information and properties of
a policy rule by reading the managed objects in the corresponding row
of the midcomRuleTable.
7.9. Asynchronous Policy Rule Event (ARE)
There are two different triggers for the ARE. It may be triggered by
the expiration of a policy rule's lifetime or the expiration of the
idle time. But beyond this, the MIDCOM-MIB implementation may
terminate a policy rule at any time. In all cases, two steps are
required for performing this transaction:
1. The MIDCOM-MIB implementation sends a midcomUnsolicitedRuleEvent
notification containing a lifetime value of 0 to the MIDCOM client
owning the rule.
2. If the midcomRuleStorageTime object in the corresponding row of
the midcomRuleTable has a value of 0, then the MIDCOM-MIB
implementation removes the row from the table. Otherwise, it sets
in this row the midcomRuleLifetime object to 0 and changes the
midcomRuleOperStatus object. If the event was triggered by policy
lifetime expiration, then the midcomRuleOperStatus is set to
timedOut(9); otherwise, it is set to terminated(11).
7.10. Group Lifetime Change (GLC)
This example explains steps that may be performed by a MIDCOM client
to change the lifetime of a policy rule group. Changing the lifetime
to 0 implies terminating all member policies of the group.
1. The MIDCOM client issues a SET request for writing the desired
lifetime to the midcomGroupLifetime object in the corresponding
row of the midcomGroupTable.
2. The MIDCOM client waits for a midcomSolicitedGroupEvent
notification concerning the corresponding row in the
midcomGroupTable. Waiting for the notification is timed out after
a pre-selected maximum waiting time. In case of a timeout while
waiting for the notification or if the client does not use
notifications, the MIDCOM client retrieves the status of the
midcomGroupEntry by one or more SNMP GET operations.
3. After receiving the midcomSolicitedRuleEvent notification, the
MIDCOM client checks the lifetime value carried by the
notification.
7.11. Group List (GL)
The SNMP agent can browse the list of policy rule groups by browsing
the midcomGroupTable. For each observed row in this table, the SNMP
agent should check the midcomGroupLifetime in order to find out if
the group does contain established policies.
7.12. Group Status (GS)
The SNMP agent can retrieve all member policies of a group by
browsing the midcomRuleTable using the midcomGroupIndex of the
particular group. For retrieving the remaining lifetime of the
group, the SNMP agent reads the midcomGroupLifetime object in the
corresponding row of the midcomGroupTable.
8. Usage Examples for Monitoring Objects
This section presents some examples that explain how a MIDCOM client
can use the midcomResourceTable to correlate policy rules with the
used middlebox resources. One example is given for middleboxes
implementing the NAT-MIB and another one is given for firewalls.
8.1. Monitoring NAT Resources
When a rule in the midcomRuleTable is executed, it directly impacts
the middlebox resources. The midcomResourceTable provides the
information on the relationships between the MIDCOM-MIB policy rules
and the middlebox resources used for enforcing these rules.
A MIDCOM-MIB policy rule will cause the creation or modification of
up to two NAT bindings and up to two NAT sessions. Two NAT bindings
are impacted in the case of a session being subject to twice-NAT.
Two NAT bindings may also be impacted when midcomRulePortRange is set
to pair(2) in the policy rule. In the majority of cases, where
traditional NAT is implemented, only a single NAT binding may be
adequate. Note, however, that this BindId is set to 0 if the
middlebox is implementing symmetric NAT function. Two NAT sessions
are created or modified only when the midcomRulePortRange is set to
pair(2) in the policy rule.
When support for the NAT-MIB module is also available at the
middlebox, the parameters in the combination of the midcomRuleTable
and the midcomResourceTable for a given rule can be used to index the
corresponding BIND and NAT session resources effected in the NAT-MIB.
These parameters are valuable to monitor the impact on the NAT
module, even when the NAT-MIB module is not implemented at the
middlebox.
The impact of MIDCOM rules on the NAT resources is important because
a MIDCOM rule not only can create BINDs and NAT sessions, but also is
capable of modifying the NAT objects that already exist. For
example, FlowDirection and MaxIdleTime parameters in a MIDCOM rule
directly affect the TranslationEntity and MaxIdleTime of the
associated NAT bind object. Likewise, MaxIdleTime in a MIDCOM rule
has a direct impact on the MaxIdleTime of the associated NAT session
object. The lifetime parameter in the MIDCOM rule directly impacts
the lifetime of all the impacted NAT BIND and NAT session objects.
8.2. Monitoring Firewall Resources
When a MIDCOM-MIB policy rule is established at a middlebox with
firewall capabilities, this may lead to the creation of one or more
new firewall rules. Note that in general a single firewall rule per
MIDCOM-MIB policy rule will be sufficient. For each policy rule, a
MIDCOM client can explore the corresponding firewall filter rule by
reading the midcomResourceEntry in the midcomResourceTable that
corresponds to the midcomRuleEntry describing the rule. The
identification of the firewall filter rule is stored in object
midcomRscFirewallRuleId. The value of midcomRscFirewallRuleId may
correspond directly to any firewall filter rule number or to an entry
in a locally available firewall MIB module.
9. Definitions
The following MIB module imports from [RFC2578], [RFC2579],
[RFC2580], [RFC2863], [RFC3411], [RFC4001], and [RFC4008].
MIDCOM-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, OBJECT-TYPE,
NOTIFICATION-TYPE, Unsigned32,
Counter32, Gauge32, mib-2
FROM SNMPv2-SMI -- RFC 2578
TEXTUAL-CONVENTION, TruthValue,
StorageType, RowStatus
FROM SNMPv2-TC -- RFC 2579
MODULE-COMPLIANCE, OBJECT-GROUP,
NOTIFICATION-GROUP
FROM SNMPv2-CONF -- RFC 2580
SnmpAdminString
FROM SNMP-FRAMEWORK-MIB -- RFC 3411
InetAddressType, InetAddress,
InetPortNumber,
InetAddressPrefixLength
FROM INET-ADDRESS-MIB -- RFC 4001
InterfaceIndexOrZero
FROM IF-MIB -- RFC 2863
NatBindIdOrZero
FROM NAT-MIB; -- RFC 4008
midcomMIB MODULE-IDENTITY
LAST-UPDATED "200708091011Z" -- August 09, 2007
ORGANIZATION "IETF Middlebox Communication Working Group"
CONTACT-INFO
"WG charter:
http://www.ietf.org/html.charters/midcom-charter.html
Mailing Lists:
General Discussion: midcom@ietf.org
To Subscribe: midcom-request@ietf.org
In Body: subscribe your_email_address
Co-editor:
Juergen Quittek
NEC Europe Ltd.
Kurfuersten-Anlage 36
69115 Heidelberg
Germany
Tel: +49 6221 4342-115
Email: quittek@nw.neclab.eu
Co-editor:
Martin Stiemerling
NEC Europe Ltd.
Kurfuersten-Anlage 36
69115 Heidelberg
Germany
Tel: +49 6221 4342-113
Email: stiemerling@nw.neclab.eu
Co-editor:
Pyda Srisuresh
Kazeon Systems, Inc.
1161 San Antonio Rd.
Mountain View, CA 94043
U.S.A.
Tel: +1 408 836-4773
Email: srisuresh@yahoo.com"
DESCRIPTION
"This MIB module defines a set of basic objects for
configuring middleboxes, such as firewalls and network
address translators, in order to enable communication
across these devices.
Managed objects defined in this MIB module are structured
in three kinds of objects:
- transaction objects required according to the MIDCOM
protocol requirements defined in RFC 3304 and according
to the MIDCOM protocol semantics defined in RFC 3989,
- configuration objects that can be used for retrieving or
setting parameters of the implementation of transaction
objects,
- optional monitoring objects that provide information
about used resource and statistics
The transaction objects are organized in two subtrees:
- objects modeling MIDCOM policy rules in the
midcomRuleTable
- objects modeling MIDCOM policy rule groups in the
midcomGroupTable
Note that typically, configuration objects are not intended
to be written by MIDCOM clients. In general, write access
to these objects needs to be restricted more strictly than
write access to objects in the transaction subtrees.
Copyright (C) The Internet Society (2008). This version
of this MIB module is part of RFC 5190; see the RFC
itself for full legal notices."
REVISION "200708091011Z" -- August 09, 2007
DESCRIPTION "Initial version, published as RFC 5190."
::= { mib-2 171 }
--
-- main components of this MIB module
--
midcomNotifications OBJECT IDENTIFIER ::= { midcomMIB 0 }
midcomObjects OBJECT IDENTIFIER ::= { midcomMIB 1 }
midcomConformance OBJECT IDENTIFIER ::= { midcomMIB 2 }
-- Transaction objects required according to the MIDCOM
-- protocol requirements defined in RFC 3304 and according to
-- the MIDCOM protocol semantics defined in RFC 3989
midcomTransaction OBJECT IDENTIFIER ::= { midcomObjects 1 }
-- Configuration objects that can be used for retrieving
-- middlebox capability information (mandatory) and for
-- setting parameters of the implementation of transaction
-- objects (optional)
midcomConfig OBJECT IDENTIFIER ::= { midcomObjects 2 }
-- Optional monitoring objects that provide information about
-- used resource and statistics
midcomMonitoring OBJECT IDENTIFIER ::= { midcomObjects 3 }
--
-- Transaction Objects
--
-- Transaction objects are structured according to the MIDCOM
-- protocol semantics into two groups:
-- - objects modeling MIDCOM policy rules in the midcomRuleTable
-- - objects modeling MIDCOM policy rule groups in the
-- midcomGroupTable
--
-- Policy rule subtree
--
-- The midcomRuleTable lists policy rules
-- including policy reserve rules and policy enable rules.
--
midcomRuleTable OBJECT-TYPE
SYNTAX SEQUENCE OF MidcomRuleEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"This table lists policy rules.
It is indexed by the midcomRuleOwner, the
midcomGroupIndex, and the midcomRuleIndex.
This implies that a rule is a member of exactly
one group and that group membership cannot
be changed.
Entries can be deleted by writing to
midcomGroupLifetime or midcomRuleLifetime
and potentially also to midcomRuleStorageTime."
::= { midcomTransaction 3 }
midcomRuleEntry OBJECT-TYPE
SYNTAX MidcomRuleEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"An entry describing a particular MIDCOM policy rule."
INDEX { midcomRuleOwner, midcomGroupIndex, midcomRuleIndex }
::= { midcomRuleTable 1 }
MidcomRuleEntry ::= SEQUENCE {
midcomRuleOwner SnmpAdminString,
midcomRuleIndex Unsigned32,
midcomRuleAdminStatus INTEGER,
midcomRuleOperStatus INTEGER,
midcomRuleStorageType StorageType,
midcomRuleStorageTime Unsigned32,
midcomRuleError SnmpAdminString,
midcomRuleInterface InterfaceIndexOrZero,
midcomRuleFlowDirection INTEGER,
midcomRuleMaxIdleTime Unsigned32,
midcomRuleTransportProtocol Unsigned32,
midcomRulePortRange INTEGER,
midcomRuleInternalIpVersion InetAddressType,
midcomRuleExternalIpVersion InetAddressType,
midcomRuleInternalIpAddr InetAddress,
midcomRuleInternalIpPrefixLength InetAddressPrefixLength,
midcomRuleInternalPort InetPortNumber,
midcomRuleExternalIpAddr InetAddress,
midcomRuleExternalIpPrefixLength InetAddressPrefixLength,
midcomRuleExternalPort InetPortNumber,
midcomRuleInsideIpAddr InetAddress,
midcomRuleInsidePort InetPortNumber,
midcomRuleOutsideIpAddr InetAddress,
midcomRuleOutsidePort InetPortNumber,
midcomRuleLifetime Unsigned32,
midcomRuleRowStatus RowStatus
}
midcomRuleOwner OBJECT-TYPE
SYNTAX SnmpAdminString (SIZE (0..32))
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The manager who owns this row in the midcomRuleTable.
This object SHOULD uniquely identify an authenticated
MIDCOM client. This object is part of the table index to
allow for the use of the SNMPv3 View-based Access Control
Model (VACM, RFC 3415)."
::= { midcomRuleEntry 1 }
midcomRuleIndex OBJECT-TYPE
SYNTAX Unsigned32 (1..4294967295)
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The value of this object must be unique in
combination with the values of the objects
midcomRuleOwner and midcomGroupIndex in this row."
::= { midcomRuleEntry 3 }
midcomRuleAdminStatus OBJECT-TYPE
SYNTAX INTEGER {
reserve(1),
enable(2),
notSet(3)
}
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The value of this object indicates the desired status of
the policy rule. See the definition of midcomRuleOperStatus
for a description of the values.
When a midcomRuleEntry is created without explicitly setting
this object, its value will be notSet(3).
However, a SET request can only set this object to either
reserve(1) or enable(2). Attempts to set this object to
notSet(3) will always fail with an 'inconsistentValue'
error. Note that this error code is SNMP specific. If the
MIB module is used with other protocols than SNMP, errors
with similar semantics specific to those protocols should
be returned.
When the midcomRuleAdminStatus object is set, then the
MIDCOM-MIB implementation will try to read the respective
relevant objects of the entry and try to achieve the
corresponding midcomRuleOperStatus.
Setting midcomRuleAdminStatus to value reserve(1) when
object midcomRuleOperStatus has a value of reserved(7)
does not have any effect on the policy rule.
Setting midcomRuleAdminStatus to value enable(2) when
object midcomRuleOperStatus has a value of enabled(8)
does not have any effect on the policy rule.
Depending on whether the midcomRuleAdminStatus is set to
reserve(1) or enable(2), several objects must be set in
advance. They serve as parameters of the policy rule to be
established.
When object midcomRuleAdminStatus is set to reserve(1),
then the following objects in the same entry are of
relevance:
- midcomRuleInterface
- midcomRuleTransportProtocol
- midcomRulePortRange
- midcomRuleInternalIpVersion
- midcomRuleExternalIpVersion
- midcomRuleInternalIpAddr
- midcomRuleInternalIpPrefixLength
- midcomRuleInternalPort
- midcomRuleLifetime
MIDCOM-MIB implementation may also consider the value
of object midcomRuleMaxIdleTime when establishing
a reserve rule.
When object midcomRuleAdminStatus is set to enable(2),
then the following objects in the same entry are of
relevance:
- midcomRuleInterface
- midcomRuleFlowDirection
- midcomRuleMaxIdleTime
- midcomRuleTransportProtocol
- midcomRulePortRange
- midcomRuleInternalIpVersion
- midcomRuleExternalIpVersion
- midcomRuleInternalIpAddr
- midcomRuleInternalIpPrefixLength
- midcomRuleInternalPort
- midcomRuleExternalIpAddr
- midcomRuleExternalIpPrefixLength
- midcomRuleExternalPort
- midcomRuleLifetime
When retrieved, the object returns the last set value.
If no value has been set, it returns the default value
notSet(3)."
DEFVAL { notSet }
::= { midcomRuleEntry 4 }
midcomRuleOperStatus OBJECT-TYPE
SYNTAX INTEGER {
newEntry(1),
setting(2),
checkingRequest(3),
incorrectRequest(4),
processingRequest(5),
requestRejected(6),
reserved(7),
enabled(8),
timedOut(9),
terminatedOnRequest(10),
terminated(11),
genericError(12)
}
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The actual status of the policy rule. The
midcomRuleOperStatus object may have the following values:
- newEntry(1) indicates that the entry in the
midcomRuleTable was created, but not modified yet.
Such an entry needs to be filled with values specifying
a request first.
- setting(2) indicates that the entry has been already
modified after generating it, but no request was made
yet.
- checkingRequest(3) indicates that midcomRuleAdminStatus
has recently been set and that the MIDCOM-MIB
implementation is currently checking the parameters of
the request. This is a transient state. The value of
this object will change to either incorrectRequest(4)
or processingRequest(5) without any external
interaction. A MIDCOM-MIB implementation MAY return
this value while checking request parameters.
- incorrectRequest(4) indicates that checking a request
resulted in detecting an incorrect value in one of the
objects containing request parameters. The failure
reason is indicated by the value of midcomRuleError.
- processingRequest(5) indicates that
midcomRuleAdminStatus has recently been set and that
the MIDCOM-MIB implementation is currently processing
the request and trying to configure the middlebox
accordingly. This is a transient state. The value of
this object will change to either requestRejected(6),
reserved(7), or enabled(8) without any external
interaction. A MIDCOM-MIB implementation MAY return
this value while processing a request.
- requestRejected(6) indicates that a request to establish
a policy rule specified by the entry was rejected. The
reason for rejection is indicated by the value of
midcomRuleError.
- reserved(7) indicates that the entry describes an
established policy reserve rule.
These values of MidcomRuleEntry are meaningful
for a reserved policy rule:
- midcomRuleMaxIdleTime
- midcomRuleInterface
- midcomRuleTransportProtocol
- midcomRulePortRange
- midcomRuleInternalIpVersion
- midcomRuleExternalIpVersion
- midcomRuleInternalIpAddr
- midcomRuleInternalIpPrefixLength
- midcomRuleInternalPort
- midcomRuleOutsideIpAddr
- midcomRuleOutsidePort
- midcomRuleLifetime
- enabled(8) indicates that the entry describes an
established policy enable rule.
These values of MidcomRuleEntry are meaningful
for an enabled policy rule:
- midcomRuleFlowDirection
- midcomRuleInterface
- midcomRuleMaxIdleTime
- midcomRuleTransportProtocol
- midcomRulePortRange
- midcomRuleInternalIpVersion
- midcomRuleExternalIpVersion
- midcomRuleInternalIpAddr
- midcomRuleInternalIpPrefixLength
- midcomRuleInternalPort
- midcomRuleExternalIpAddr
- midcomRuleExternalIpPrefixLength
- midcomRuleExternalPort
- midcomRuleInsideIpAddr
- midcomRuleInsidePort
- midcomRuleOutsideIpAddr
- midcomRuleOutsidePort
- midcomRuleLifetime
- timedOut(9) indicates that the lifetime of a previously
established policy rule has expired and that the policy
rule is terminated for this reason.
- terminatedOnRequest(10) indicates that a previously
established policy rule was terminated by an SNMP
manager setting the midcomRuleLifetime to 0 or
setting midcomGroupLifetime to 0.
- terminated(11) indicates that a previously established
policy rule was terminated by the MIDCOM-MIB
implementation for a reason other than lifetime
expiration or an explicit request from a MIDCOM client.
- genericError(12) indicates that the policy rule
specified by the entry is not established due to
an error condition not listed above.
The states timedOut(9), terminatedOnRequest(10), and
terminated(11) are referred to as termination states.
The states incorrectRequest(4), requestRejected(6),
and genericError(12) are referred to as error states.
The checkingRequest(3) and processingRequest(5)
states are transient states, which will lead to either
one of the error states or the reserved(7) state or the
enabled(8) state. MIDCOM-MIB implementations MAY return
these values when checking or processing requests."
DEFVAL { newEntry }
::= { midcomRuleEntry 5 }
midcomRuleStorageType OBJECT-TYPE
SYNTAX StorageType
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"When retrieved, this object returns the storage
type of the policy rule. Writing to this object can
change the storage type of the particular row from
volatile(2) to nonVolatile(3) or vice versa.
Attempts to set this object to permanent will always
fail with an 'inconsistentValue' error. Note that this
error code is SNMP specific. If the MIB module is used
with other protocols than SNMP, errors with similar
semantics specific to those protocols should be
returned.
If midcomRuleStorageType has the value permanent(4),
then all objects in this row whose MAX-ACCESS value
is read-create must be read-only."
DEFVAL { volatile }
::= { midcomRuleEntry 6 }
midcomRuleStorageTime OBJECT-TYPE
SYNTAX Unsigned32
UNITS "seconds"
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The value of this object specifies how long this row
can exist in the midcomRuleTable after the
midcomRuleOperStatus switched to a termination state or
to an error state. This object returns the remaining
time that the row may exist before it is aged out.
After expiration or termination of the context, the value
of this object ticks backwards. The entry in the
midcomRuleTable is destroyed when the value reaches 0.
The value of this object may be set in order to increase
or reduce the remaining time that the row may exist.
Setting the value to 0 will destroy this entry as soon as
the midcomRuleOperStatus switched to a termination state
or to an error state.
Note that there is no guarantee that the row is stored as
long as this object indicates. At any time, the MIDCOM-
MIB implementation may decide to remove a row describing
a terminated policy rule before the storage time of the
corresponding row in the midcomRuleTable reaches the
value of 0. In this case, the information stored in this
row is not available anymore.
If object midcomRuleStorageType indicates that the policy
rule has the storage type permanent(4), then this object has
a constant value of 4294967295."
DEFVAL { 0 }
::= { midcomRuleEntry 7 }
midcomRuleError OBJECT-TYPE
SYNTAX SnmpAdminString
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"This object contains a descriptive error message if
the transition into the operational status reserved(7)
or enabled(8) failed. Implementations must reset the
error message to a zero-length string when a new
attempt to change the policy rule status to reserved(7)
or enabled(8) is started.
RECOMMENDED values to be returned in particular cases
include
- 'lack of IP addresses'
- 'lack of port numbers'
- 'lack of resources'
- 'specified NAT interface does not exist'
- 'specified NAT interface does not support NAT'
- 'conflict with already existing policy rule'
- 'no internal IP wildcarding allowed'
- 'no external IP wildcarding allowed'
The semantics of these error messages and the corresponding
behavior of the MIDCOM-MIB implementation are specified
in sections 2.3.9 and 2.3.10 of RFC 3989."
REFERENCE
"RFC 3989, sections 2.3.9 and 2.3.10"
DEFVAL { ''H }
::= { midcomRuleEntry 8 }
midcomRuleInterface OBJECT-TYPE
SYNTAX InterfaceIndexOrZero
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"This object indicates the IP interface for which
enforcement of a policy rule is requested or performed,
respectively.
The interface is identified by its index in the ifTable
(see IF-MIB in RFC 2863). If the object has a value of 0,
then no particular interface is indicated.
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule.
If object midcomRuleOperStatus of the same entry has the
value newEntry(1) or setting(2), then this object can be
written by a manager in order to request its preference
concerning the interface at which it requests NAT service.
The default value of 0 indicates that the manager does not
have a preferred interface or does not have sufficient
topology information for specifying one. Writing to this
object in any state other than newEntry(1) or setting(2)
will always fail with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value reserved(7) or enabled(8), then this object indicates
the interface at which NAT service for this rule is
performed. If NAT service is not required for enforcing
the policy rule, then the value of this object is 0. Also,
if the MIDCOM-MIB implementation cannot indicate an
interface, because it does not have this information or
because NAT service is not offered at a particular single
interface, then the value of the object is 0.
Note that the index of a particular interface in the
ifTable may change after a re-initialization of the
middlebox, for example, after adding another interface to
it. In such a case, the value of this object may change,
but the interface referred to by the MIDCOM-MIB MUST still
be the same. If, after a re-initialization of the
middlebox, the interface referred to before
re-initialization cannot be uniquely mapped anymore to a
particular entry in the ifTable, then the value of object
midcomRuleOperStatus of the same entry MUST be changed to
terminated(11).
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7), or
enabled(8), then the value of this object is irrelevant."
DEFVAL { 0 }
::= { midcomRuleEntry 9 }
midcomRuleFlowDirection OBJECT-TYPE
SYNTAX INTEGER {
inbound(1),
outbound(2),
biDirectional(3)
}
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"This parameter specifies the direction of enabled
communication, either inbound(1), outbound(2), or
biDirectional(3).
The semantics of this object depends on the protocol
the rule relates to. If the rule is independent of
the transport protocol (midcomRuleTransportProtocol
has a value of 0) or if the transport protocol is UDP,
then the value of midcomRuleFlowDirection indicates
the direction of packets traversing the middlebox.
In this case, value inbound(1) indicates that packets
are traversing from outside to inside, value outbound(2)
indicates that packets are traversing from inside to
outside. For both values, inbound(1) and outbound(2)
packets can traverse the middlebox only unidirectional.
A bidirectional flow is indicated by value
biDirectional(3).
If the transport protocol is TCP, the packet flow is
always bidirectional, but the value of
midcomRuleFlowDirection indicates that:
- inbound(1): bidirectional TCP packet flow.
First packet, with TCP SYN flag set, must arrive
at an outside interface of the middlebox.
- outbound(2): bidirectional TCP packet flow.
First packet, with TCP SYN flag set, must arrive
at an inside interface of the middlebox.
- biDirectional(3): bidirectional TCP packet flow.
First packet, with TCP SYN flag set, may arrive
at an inside or an outside interface of the middlebox.
This object is used as input to a request for
establishing a policy enable rule as well as for
indicating the properties of an established policy rule.
If object midcomRuleOperStatus of the same entry has a
value of either newEntry(1), setting(2), or reserved(7),
then this object can be written by a manager in order to
specify a requested direction to be enabled by a policy
rule. Writing to this object in any state other than
newEntry(1), setting(2), or reserved(7) will always fail
with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value enabled(8), then this object indicates the enabled
flow direction.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7), or
enabled(8), then the value of this object is irrelevant."
DEFVAL { outbound }
::= { midcomRuleEntry 10 }
midcomRuleMaxIdleTime OBJECT-TYPE
SYNTAX Unsigned32
UNITS "seconds"
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"Maximum idle time of the policy rule in seconds.
If no packet to which the policy rule applies passes the
middlebox for the specified midcomRuleMaxIdleTime, then
the policy rule enters the termination state timedOut(9).
A value of 0 indicates that the policy does not require
an individual idle time and that instead, a default idle
time chosen by the middlebox is used.
A value of 4294967295 ( = 2^32 - 1 ) indicates that the
policy does not time out if it is idle.
This object is used as input to a request for
establishing a policy enable rule as well as for
indicating the properties of an established policy rule.
If object midcomRuleOperStatus of the same entry has a
value of either newEntry(1), setting(2), or reserved(7),
then this object can be written by a manager in order to
specify a maximum idle time for the policy rule to be
requested. Writing to this object in any state others
than newEntry(1), setting(2), or reserved(7) will always
fail with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value enabled(8), then this object indicates the maximum
idle time of the policy rule. Note that even if a maximum
idle time greater than zero was requested, the middlebox
may not be able to support maximum idle times and set the
value of this object to zero when entering state
enabled(8).
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7), or
enabled(8), then the value of this object is irrelevant."
DEFVAL { 0 }
::= { midcomRuleEntry 11 }
midcomRuleTransportProtocol OBJECT-TYPE
SYNTAX Unsigned32 (0..255)
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The transport protocol.
Valid values for midcomRuleTransportProtocol
other than zero are defined at:
http://www.iana.org/assignments/protocol-numbers
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule.
If object midcomRuleOperStatus of the same entry has a
value of either newEntry(1) or setting(2), then this
object can be written by a manager in order to specify a
requested transport protocol. If translation of an IP
address only is requested, then this object must have the
default value 0. Writing to this object in any state
other than newEntry(1) or setting(2) will always fail
with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value reserved(7) or enabled(8), then this object
indicates which transport protocol is enforced by this
policy rule. A value of 0 indicates a rule acting on IP
addresses only.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7), or
enabled(8), then the value of this object is irrelevant."
DEFVAL { 0 }
::= { midcomRuleEntry 12 }
midcomRulePortRange OBJECT-TYPE
SYNTAX INTEGER {
single(1),
pair(2)
}
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The range of port numbers.
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule. It is relevant to the
operation of the MIDCOM-MIB implementation only if the
value of object midcomTransportProtocol in the same entry
has a value other than 0.
If object midcomRuleOperStatus of the same entry has the
value newEntry(1) or setting(2), then this object can be
written by a manager in order to specify the requested
size of the port range. With single(1) just a single
port number is requested, with pair(2) a consecutive pair
of port numbers is requested with the lower number being
even. Requesting a consecutive pair of port numbers may
be used by RTP [RFC3550] and may even be required to
support older RTP applications.
Writing to this object in any state other than
newEntry(1), setting(2) or reserved(7) will always fail
with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has a
value of either reserved(7) or enabled(8), then this
object will have the value that it had before the
transition to this state.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7), or
enabled(8), then the value of this object is irrelevant."
DEFVAL { single }
::= { midcomRuleEntry 13}
midcomRuleInternalIpVersion OBJECT-TYPE
SYNTAX InetAddressType
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"IP version of the internal address (A0) and the inside
address (A1). Allowed values are ipv4(1), ipv6(2),
ipv4z(3), and ipv6z(4).
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule.
If object midcomRuleOperStatus of the same entry has the
value newEntry(1) or setting(2), then this object can be
written by a manager in order to specify the IP version
required at the inside of the middlebox. Writing to this
object in any state other than newEntry(1) or setting(2)
will always fail with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value reserved(7) or enabled(8), then this object
indicates the internal/inside IP version.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7), or
enabled(8), then the value of this object is irrelevant."
DEFVAL { ipv4 }
::= { midcomRuleEntry 14 }
midcomRuleExternalIpVersion OBJECT-TYPE
SYNTAX InetAddressType
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"IP version of the external address (A3) and the outside
address (A2). Allowed values are ipv4(1) and ipv6(2).
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule.
If object midcomRuleOperStatus of the same entry has the
value newEntry(1) or setting(2), then this object can be
written by a manager in order to specify the IP version
required at the outside of the middlebox. Writing to
this object in any state other than newEntry(1) or
setting(2) will always fail with an 'inconsistentValue'
error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value reserved(7) or enabled(8), then this object
indicates the external/outside IP version.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7) or
enabled(8), then the value of this object is irrelevant."
DEFVAL { ipv4 }
::= { midcomRuleEntry 15 }
midcomRuleInternalIpAddr OBJECT-TYPE
SYNTAX InetAddress
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The internal IP address (A0).
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule.
If object midcomRuleOperStatus of the same entry has the
value newEntry(1) or setting(2), then this object can be
written by a manager in order to specify the internal IP
address for which a reserve policy rule or a enable policy
rule is requested to be established. Writing to this
object in any state other than newEntry(1) or setting(2)
will always fail with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value reserved(7) or enabled(8), then this object will
have the value which it had before the transition to this
state.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7) or
enabled(8), then the value of this object is irrelevant."
::= { midcomRuleEntry 16 }
midcomRuleInternalIpPrefixLength OBJECT-TYPE
SYNTAX InetAddressPrefixLength
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The prefix length of the internal IP address used for
wildcarding. A value of 0 indicates a full wildcard;
in this case, the value of midcomRuleInternalIpAddr is
irrelevant. If midcomRuleInternalIpVersion has a value
of ipv4(1), then a value > 31 indicates no wildcarding
at all. If midcomRuleInternalIpVersion has a value
of ipv4(2), then a value > 127 indicates no wildcarding
at all. A MIDCOM-MIB implementation that does not
support IP address wildcarding MUST implement this object
as read-only with a value of 128. A MIDCOM that does
not support wildcarding based on prefix length MAY
restrict allowed values for this object to 0 and 128.
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule.
If object midcomRuleOperStatus of the same entry has the
value newEntry(1) or setting(2), then this object can be
written by a manager in order to specify the prefix length
of the internal IP address for which a reserve policy rule
or an enable policy rule is requested to be established.
Writing to this object in any state other than newEntry(1)
or setting(2) will always fail with an 'inconsistentValue'
error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value reserved(7) or enabled(8), then this object will
have the value which it had before the transition to this
state.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7), or
enabled(8), then the value of this object is irrelevant."
DEFVAL { 128 }
::= { midcomRuleEntry 17 }
midcomRuleInternalPort OBJECT-TYPE
SYNTAX InetPortNumber
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The internal port number. A value of 0 is a wildcard.
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule. It is relevant to the
operation of the MIDCOM-MIB implementation only if the
value of object midcomTransportProtocol in the same entry
has a value other than 0.
If object midcomRuleOperStatus of the same entry has the
value newEntry(1) or setting(2), then this object can be
written by a manager in order to specify the internal port
number for which a reserve policy rule or an enable policy
rule is requested to be established. Writing to this
object in any state other than newEntry(1) or setting(2)
will always fail with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value reserved(7) or enabled(8), then this object will
have the value that it had before the transition to this
state.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7), or
enabled(8), then the value of this object is irrelevant."
DEFVAL { 0 }
::= { midcomRuleEntry 18 }
midcomRuleExternalIpAddr OBJECT-TYPE
SYNTAX InetAddress
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The external IP address (A3).
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule.
If object midcomRuleOperStatus of the same entry has the
value newEntry(1), setting(2), or reserved(7), then this
object can be written by a manager in order to specify the
external IP address for which an enable policy rule is
requested to be established. Writing to this object in
any state other than newEntry(1), setting(2), or reserved(7)
will always fail with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value enabled(8), then this object will have the value
that it had before the transition to this state.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7), or
enabled(8), then the value of this object is irrelevant."
::= { midcomRuleEntry 19 }
midcomRuleExternalIpPrefixLength OBJECT-TYPE
SYNTAX InetAddressPrefixLength
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The prefix length of the external IP address used for
wildcarding. A value of 0 indicates a full wildcard;
in this case, the value of midcomRuleExternalIpAddr is
irrelevant. If midcomRuleExternalIpVersion has a value
of ipv4(1), then a value > 31 indicates no wildcarding
at all. If midcomRuleExternalIpVersion has a value
of ipv4(2), then a value > 127 indicates no wildcarding
at all. A MIDCOM-MIB implementation that does not
support IP address wildcarding MUST implement this object
as read-only with a value of 128. A MIDCOM that does
not support wildcarding based on prefix length MAY
restrict allowed values for this object to 0 and 128.
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule.
If object midcomRuleOperStatus of the same entry has the
value newEntry(1), setting(2), or reserved(7), then this
object can be written by a manager in order to specify the
prefix length of the external IP address for which an
enable policy rule is requested to be established.
Writing to this object in any state other than
newEntry(1), setting(2), or reserved(7) will always fail
with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value enabled(8), then this object will have the value
that it had before the transition to this state.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7), or
enabled(8), then the value of this object is irrelevant."
DEFVAL { 128 }
::= { midcomRuleEntry 20 }
midcomRuleExternalPort OBJECT-TYPE
SYNTAX InetPortNumber
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The external port number. A value of 0 is a wildcard.
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule. It is relevant to the
operation of the MIDCOM-MIB implementation only if the
value of object midcomTransportProtocol in the same entry
has a value other than 0.
If object midcomRuleOperStatus of the same entry has the
value newEntry(1), setting(2) or reserved(7), then this
object can be written by a manager in order to specify the
external port number for which an enable policy rule is
requested to be established. Writing to this object in
any state other than newEntry(1), setting(2) or reserved(7)
will always fail with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has the
value enabled(8), then this object will have the value
which it had before the transition to this state.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7) or
enabled(8), then the value of this object is irrelevant."
DEFVAL { 0 }
::= { midcomRuleEntry 21 }
midcomRuleInsideIpAddr OBJECT-TYPE
SYNTAX InetAddress
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The inside IP address at the middlebox (A1).
The value of this object is relevant only if
object midcomRuleOperStatus of the same entry has
a value of either reserved(7) or enabled(8)."
::= { midcomRuleEntry 22 }
midcomRuleInsidePort OBJECT-TYPE
SYNTAX InetPortNumber
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The inside port number at the middlebox.
A value of 0 is a wildcard.
The value of this object is relevant only if
object midcomRuleOperStatus of the same entry has
a value of either reserved(7) or enabled(8)."
::= { midcomRuleEntry 23 }
midcomRuleOutsideIpAddr OBJECT-TYPE
SYNTAX InetAddress
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The outside IP address at the middlebox (A2).
The value of this object is relevant only if
object midcomRuleOperStatus of the same entry has
a value of either reserved(7) or enabled(8)."
::= { midcomRuleEntry 24 }
midcomRuleOutsidePort OBJECT-TYPE
SYNTAX InetPortNumber
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The outside port number at the middlebox.
A value of 0 is a wildcard.
The value of this object is relevant only if
object midcomRuleOperStatus of the same entry has
a value of either reserved(7) or enabled(8)."
::= { midcomRuleEntry 25 }
midcomRuleLifetime OBJECT-TYPE
SYNTAX Unsigned32
UNITS "seconds"
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"The remaining lifetime in seconds of this policy rule.
Lifetime of a policy rule starts when object
midcomRuleOperStatus in the same entry enters either
state reserved(7) or state enabled(8).
This object is used as input to a request for establishing
a policy rule as well as for indicating the properties of
an established policy rule.
If object midcomRuleOperStatus of the same entry has a
value of either newEntry(1) or setting(2), then this
object can be written by a manager in order to specify
the requested lifetime of a policy rule to be established.
If object midcomRuleOperStatus of the same entry has a
value of either reserved(7) or enabled(8), then this
object indicates the (continuously decreasing) remaining
lifetime of the established policy rule. Note that when
entering state reserved(7) or enabled(8), the MIDCOM-MIB
implementation can choose a lifetime shorter than the one
requested.
Unlike other parameters of the policy rule, this parameter
can still be written in state reserved(7) and enabled(8).
Writing to this object is processed by the MIDCOM-MIB
implementation by choosing a lifetime value that is
greater than 0 and less than or equal to the minimum of
the requested value and the value specified by object
midcomConfigMaxLifetime:
0 <= lt_granted <= MINIMUM(lt_requested, lt_maximum)
where:
- lt_granted is the actually granted lifetime by the
MIDCOM-MIB implementation
- lt_requested is the requested lifetime of the MIDCOM
client
- lt_maximum is the value of object
midcomConfigMaxLifetime
SNMP SET requests to this object may be rejected or the
value of the object after an accepted SET operation may be
less than the value that was contained in the SNMP SET
request.
Successfully writing a value of 0 terminates the policy
rule. Note that after a policy rule is terminated, still
the entry will exist as long as indicated by the value of
midcomRuleStorageTime.
Writing to this object in any state other than
newEntry(1), setting(2), reserved(7), or enabled(7)
will always fail with an 'inconsistentValue' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
If object midcomRuleOperStatus of the same entry has a
value other than newEntry(1), setting(2), reserved(7), or
enabled(8), then the value of this object is irrelevant."
DEFVAL { 180 }
::= { midcomRuleEntry 26 }
midcomRuleRowStatus OBJECT-TYPE
SYNTAX RowStatus
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"A control that allows entries to be added and removed from
this table.
Entries can also be removed from this table by setting
objects midcomRuleLifetime and midcomRuleStorageTime of
an entry to 0.
Attempts to set a row notInService(2) where the value
of the midcomRuleStorageType object is permanent(4) or
readOnly(5) will result in an 'notWritable' error.
Note that this error code is SNMP specific. If the MIB
module is used with other protocols than SNMP, errors with
similar semantics specific to those protocols should be
returned.
The value of this object has no effect on whether other
objects in this conceptual row can be modified."
::= { midcomRuleEntry 27 }
--
-- Policy rule group subtree
--
-- The midcomGroupTable lists all current policy rule groups.
--
midcomGroupTable OBJECT-TYPE
SYNTAX SEQUENCE OF MidcomGroupEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"This table lists all current policy rule groups.
Entries in this table are created or removed
implicitly when entries in the midcomRuleTable are
created or removed, respectively. A group entry
in this table only exists as long as there are
member rules of this group in the midcomRuleTable.
The table serves for listing the existing groups and
their remaining lifetimes and for changing lifetimes
of groups and implicitly of all group members.
Groups and all their member policy rules can only be
deleted by deleting all member policies in the
midcomRuleTable.
Setting midcomGroupLifetime will result in setting
the lifetime of all policy members to the same value."
::= { midcomTransaction 4 }
midcomGroupEntry OBJECT-TYPE
SYNTAX MidcomGroupEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"An entry describing properties of a particular
MIDCOM policy rule group."
INDEX { midcomRuleOwner, midcomGroupIndex }
::= { midcomGroupTable 1 }
MidcomGroupEntry ::= SEQUENCE {
midcomGroupIndex Unsigned32,
midcomGroupLifetime Unsigned32
}
midcomGroupIndex OBJECT-TYPE
SYNTAX Unsigned32 (1..4294967295)
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The index of this group for the midcomRuleOwner.
A group is identified by the combination of
midcomRuleOwner and midcomGroupIndex.
The value of this index must be unique per
midcomRuleOwner."
::= { midcomGroupEntry 2 }
midcomGroupLifetime OBJECT-TYPE
SYNTAX Unsigned32
UNITS "seconds"
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"When retrieved, this object delivers the maximum
lifetime in seconds of all member rules of this group,
i.e., of all rows in the midcomRuleTable that have the
same values for midcomRuleOwner and midcomGroupIndex.
Successfully writing to this object modifies the
lifetime of all member policies. Successfully
writing a value of 0 terminates all member policies
and implicitly deletes the group as soon as all member
entries are removed from the midcomRuleTable.
Note that after a group's lifetime is expired or is
set to 0, still the corresponding entry in the
midcomGroupTable will exist as long as terminated
member policy rules are stored as entries in the
midcomRuleTable.
Writing to this object is processed by the MIDCOM-MIB
implementation by choosing a lifetime value that is
greater than 0 and less than or equal to the minimum of
the requested value and the value specified by object
midcomConfigMaxLifetime:
0 <= lt_granted <= MINIMUM(lt_requested, lt_maximum)
where:
- lt_granted is the actually granted lifetime by the
MIDCOM-MIB implementation
- lt_requested is the requested lifetime of the MIDCOM
client
- lt_maximum is the value of object
midcomConfigMaxLifetime
SNMP SET requests to this object may be rejected or the
value of the object after an accepted SET operation may be
less than the value that was contained in the SNMP SET
request."
::= { midcomGroupEntry 3 }
--
-- Configuration Objects
--
-- Configuration objects that can be used for retrieving
-- middlebox capability information (mandatory) and for
-- setting parameters of the implementation of transaction
-- objects (optional).
--
-- Note that typically configuration objects are not intended
-- to be written by MIDCOM clients. In general, write access
-- to these objects needs to be restricted more strictly than
-- write access to transaction objects.
--
--
-- Capabilities subtree
--
-- This subtree contains objects to which MIDCOM clients should
-- have read access.
--
midcomConfigMaxLifetime OBJECT-TYPE
SYNTAX Unsigned32
UNITS "seconds"
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"When retrieved, this object returns the maximum lifetime,
in seconds, that this middlebox allows policy rules to
have."
::= { midcomConfig 1 }
midcomConfigPersistentRules OBJECT-TYPE
SYNTAX TruthValue
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"When retrieved, this object returns true(1) if the
MIDCOM-MIB implementation can store policy rules
persistently. Otherwise, it returns false(2).
A value of true(1) indicates that there may be
entries in the midcomRuleTable with object
midcomRuleStorageType set to value nonVolatile(3)."
::= { midcomConfig 2 }
midcomConfigIfTable OBJECT-TYPE
SYNTAX SEQUENCE OF MidcomConfigIfEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"This table indicates capabilities of the MIDCOM-MIB
implementation per IP interface.
The table is indexed by the object midcomConfigIfIndex.
For indexing a single interface, this object contains
the value of the ifIndex object that is associated
with the interface. If an entry with
midcomConfigIfIndex = 0 occurs, then bits set in
objects of this entry apply to all interfaces for which
there is no entry in this table with the interface's
index."
::= { midcomConfig 3 }
midcomConfigIfEntry OBJECT-TYPE
SYNTAX MidcomConfigIfEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"An entry describing the capabilities of a middlebox
with respect to the indexed IP interface."
INDEX { midcomConfigIfIndex }
::= { midcomConfigIfTable 1 }
MidcomConfigIfEntry ::= SEQUENCE {
midcomConfigIfIndex InterfaceIndexOrZero,
midcomConfigIfBits BITS,
midcomConfigIfEnabled TruthValue
}
midcomConfigIfIndex OBJECT-TYPE
SYNTAX InterfaceIndexOrZero
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The index of an entry in the midcomConfigIfTable.
For values different from zero, this object
identifies an IP interface by containing the same
value as the ifIndex object associated with the
interface.
Note that the index of a particular interface in the
ifTable may change after a re-initialization of the
middlebox, for example, after adding another interface to
it. In such a case, the value of this object may change,
but the interface referred to by the MIDCOM-MIB MUST still
be the same. If, after a re-initialization of the
middlebox, the interface referred to before
re-initialization cannot be uniquely mapped anymore to a
particular entry in the ifTable, then the value of object
midcomConfigIfEnabled of the same entry MUST be changed to
false(2).
If the object has a value of 0, then values
specified by further objects of the same entry
apply to all interfaces for which there is no
explicit entry in the midcomConfigIfTable."
::= { midcomConfigIfEntry 1 }
midcomConfigIfBits OBJECT-TYPE
SYNTAX BITS {
ipv4(0),
ipv6(1),
addressWildcards(2),
portWildcards(3),
firewall(4),
nat(5),
portTranslation(6),
protocolTranslation(7),
twiceNat(8),
inside(9)
}
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"When retrieved, this object returns a set of bits
indicating the capabilities (or configuration) of
the middlebox with respect to the referenced IP interface.
If the index equals 0, then all set bits apply to all
interfaces.
If the ipv4(0) bit is set, then the middlebox supports
IPv4 at the indexed IP interface.
If the ipv6(1) bit is set, then the middlebox supports
IPv6 at the indexed IP interface.
If the addressWildcards(2) bit is set, then the
middlebox supports IP address wildcarding at the indexed
IP interface.
If the portWildcards(3) bit is set, then the
middlebox supports port wildcarding at the indexed
IP interface.
If the firewall(4) bit is set, then the middlebox offers
firewall functionality at the indexed interface.
If the nat(5) bit is set, then the middlebox offers
network address translation service at the indexed
interface.
If the portTranslation(6) bit is set, then the middlebox
offers port translation service at the indexed interface.
This bit is only relevant if nat(5) is set.
If the protocolTranslation(7) bit is set, then the
middlebox offers protocol translation service between
IPv4 and IPv6 at the indexed interface. This bit is only
relevant if nat(5) is set.
If the twiceNat(8) bit is set, then the middlebox offers
twice network address translation service at the indexed
interface. This bit is only relevant if nat(5) is set.
If the inside(9) bit is set, then the indexed interface is
an inside interface with respect to NAT functionality.
Otherwise, it is an outside interface. This bit is only
relevant if nat(5) is set. An SNMP agent supporting both
the MIDCOM-MIB module and the NAT-MIB module SHOULD ensure
that the value of this object is consistent with the values
of corresponding objects in the NAT-MIB module."
::= { midcomConfigIfEntry 2 }
midcomConfigIfEnabled OBJECT-TYPE
SYNTAX TruthValue
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"The value of this object indicates the availability of
the middlebox service described by midcomConfigIfBits
at the indexed IP interface.
By writing to this object, the MIDCOM support for the
entire IP interface can be switched on or off. Setting
this object to false(2) immediately stops middlebox
support at the indexed IP interface. This implies that
all policy rules that use NAT or firewall resources at
the indexed IP interface are terminated immediately.
In this case, the MIDCOM agent MUST send
midcomUnsolicitedRuleEvent to all MIDCOM clients that
have access to one of the terminated rules."
DEFVAL { true }
::= { midcomConfigIfEntry 3 }
--
-- Firewall subtree
--
-- This subtree contains the firewall configuration table
--
midcomConfigFirewallTable OBJECT-TYPE
SYNTAX SEQUENCE OF MidcomConfigFirewallEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"This table lists the firewall configuration per IP interface.
It can be used for configuring how policy rules created by
MIDCOM clients are realized as firewall rules of a firewall
implementation. Particularly, the priority used for MIDCOM
policy rules can be configured. For a single firewall
implementation at a particular IP interface, all MIDCOM
policy rules are realized as firewall rules with the same
priority. Also, a firewall rule group name can be
configured.
The table is indexed by the object midcomConfigFirewallIndex.
For indexing a single interface, this object contains the
value of the ifIndex object that is associated with the
interface. If an entry with midcomConfigFirewallIndex = 0
occurs, then bits set in objects of this entry apply to all
interfaces for which there is no entry in this table for the
interface's index."
::= { midcomConfig 4 }
midcomConfigFirewallEntry OBJECT-TYPE
SYNTAX MidcomConfigFirewallEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"An entry describing a particular set of
firewall resources."
INDEX { midcomConfigFirewallIndex }
::= { midcomConfigFirewallTable 1 }
MidcomConfigFirewallEntry ::= SEQUENCE {
midcomConfigFirewallIndex InterfaceIndexOrZero,
midcomConfigFirewallGroupId SnmpAdminString,
midcomConfigFirewallPriority Unsigned32
}
midcomConfigFirewallIndex OBJECT-TYPE
SYNTAX InterfaceIndexOrZero
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The index of an entry in the midcomConfigFirewallTable.
For values different from 0, this object identifies an
IP interface by containing the same value as the ifIndex
object associated with the interface.
Note that the index of a particular interface in the
ifTable may change after a re-initialization of the
middlebox, for example, after adding another interface to
it. In such a case, the value of this object may change,
but the interface referred to by the MIDCOM-MIB MUST still
be the same. If, after a re-initialization of the
middlebox, the interface referred to before
re-initialization cannot be uniquely mapped anymore to a
particular entry in the ifTable, then the entry in the
midcomConfigFirewallTable MUST be deleted.
If the object has a value of 0, then values specified by
further objects of the same entry apply to all interfaces
for which there is no explicit entry in the
midcomConfigFirewallTable."
::= { midcomConfigFirewallEntry 1 }
midcomConfigFirewallGroupId OBJECT-TYPE
SYNTAX SnmpAdminString
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"The firewall rule group to which all firewall rules are
assigned that the MIDCOM server creates for the interface
indicated by object midcomConfigFirewallIndex. If the
value of object midcomConfigFirewallIndex is 0, then all
firewall rules of the MIDCOM server that are created for
interfaces with no specific entry in the
midcomConfigFirewallTable are assigned to the firewall
rule group indicated by the value of this object."
::= { midcomConfigFirewallEntry 2 }
midcomConfigFirewallPriority OBJECT-TYPE
SYNTAX Unsigned32
MAX-ACCESS read-write
STATUS current
DESCRIPTION
"The priority assigned to all firewall rules that the
MIDCOM server creates for the interface indicated by
object midcomConfigFirewallIndex. If the value of object
midcomConfigFirewallIndex is 0, then this priority is
assigned to all firewall rules of the MIDCOM server that
are created for interfaces for which there is no specific
entry in the midcomConfigFirewallTable."
::= { midcomConfigFirewallEntry 3 }
--
-- Monitoring Objects
--
-- Monitoring objects are structured into two groups,
-- the midcomResourceGroup providing information about used
-- resources and the midcomStatisticsGroup providing information
-- about MIDCOM transaction statistics.
--
-- Resources subtree
--
-- The MIDCOM resources subtree contains a set of managed
-- objects describing the currently used resources of NAT
-- and firewall implementations.
--
--
-- Textual conventions for objects of the resource subtree
--
MidcomNatBindMode ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"An indicator of the kind of NAT resources used by a policy
rule. This definition corresponds to the definition of
NatBindMode in the NAT-MIB (RFC 4008). Value none(3) can
be used to indicate that the policy rule does not use
any NAT binding.
"
SYNTAX INTEGER {
addressBind(1),
addressPortBind(2),
none(3)
}
MidcomNatSessionIdOrZero ::= TEXTUAL-CONVENTION
DISPLAY-HINT "d"
STATUS current
DESCRIPTION
"A unique ID that is assigned to each NAT session by
a NAT implementation. This definition corresponds to
the definition of NatSessionId in the NAT-MIB (RFC 4008).
Value 0 can be used to indicate that the policy rule does
not use any NAT binding."
SYNTAX Unsigned32
--
-- The MIDCOM resource table
--
midcomResourceTable OBJECT-TYPE
SYNTAX SEQUENCE OF MidcomResourceEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"This table lists all used middlebox resources per
MIDCOM policy rule.
The midcomResourceTable augments the
midcomRuleTable."
::= { midcomMonitoring 1 }
midcomResourceEntry OBJECT-TYPE
SYNTAX MidcomResourceEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"An entry describing a particular set of middlebox
resources."
AUGMENTS { midcomRuleEntry }
::= { midcomResourceTable 1 }
MidcomResourceEntry ::= SEQUENCE {
midcomRscNatInternalAddrBindMode MidcomNatBindMode,
midcomRscNatInternalAddrBindId NatBindIdOrZero,
midcomRscNatInsideAddrBindMode MidcomNatBindMode,
midcomRscNatInsideAddrBindId NatBindIdOrZero,
midcomRscNatSessionId1 MidcomNatSessionIdOrZero,
midcomRscNatSessionId2 MidcomNatSessionIdOrZero,
midcomRscFirewallRuleId Unsigned32
}
midcomRscNatInternalAddrBindMode OBJECT-TYPE
SYNTAX MidcomNatBindMode
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"An indication of whether this policy rule uses an address
NAT bind or an address-port NAT bind for binding the
internal address.
If the MIDCOM-MIB module is operated together with
the NAT-MIB module (RFC 4008) then object
midcomRscNatInternalAddrBindMode contains the same
value as the corresponding object
natSessionPrivateSrcEPBindMode of the NAT-MIB module."
::= { midcomResourceEntry 4 }
midcomRscNatInternalAddrBindId OBJECT-TYPE
SYNTAX NatBindIdOrZero
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"This object references to the allocated internal NAT
bind that is used by this policy rule. A NAT bind
describes the mapping of internal addresses to
outside addresses. MIDCOM-MIB implementations can
read this object to learn the corresponding NAT bind
resource for this particular policy rule.
If the MIDCOM-MIB module is operated together with
the NAT-MIB module (RFC 4008) then object
midcomRscNatInternalAddrBindId contains the same
value as the corresponding object
natSessionPrivateSrcEPBindId of the NAT-MIB module."
::= { midcomResourceEntry 5 }
midcomRscNatInsideAddrBindMode OBJECT-TYPE
SYNTAX MidcomNatBindMode
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"An indication of whether this policy rule uses an address
NAT bind or an address-port NAT bind for binding the
external address.
If the MIDCOM-MIB module is operated together with
the NAT-MIB module (RFC 4008), then object
midcomRscNatInsideAddrBindMode contains the same
value as the corresponding object
natSessionPrivateDstEPBindMode of the NAT-MIB module."
::= { midcomResourceEntry 6 }
midcomRscNatInsideAddrBindId OBJECT-TYPE
SYNTAX NatBindIdOrZero
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"This object refers to the allocated external NAT
bind that is used by this policy rule. A NAT bind
describes the mapping of external addresses to
inside addresses. MIDCOM-MIB implementations can
read this object to learn the corresponding NAT bind
resource for this particular policy rule.
If the MIDCOM-MIB module is operated together with the
NAT-MIB module (RFC 4008), then object
midcomRscNatInsideAddrBindId contains the same
value as the corresponding object
natSessionPrivateDstEPBindId of the NAT-MIB module."
::= { midcomResourceEntry 7 }
midcomRscNatSessionId1 OBJECT-TYPE
SYNTAX MidcomNatSessionIdOrZero
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"This object refers to the first allocated NAT session for
this policy rule. MIDCOM-MIB implementations can read this
object to learn whether or not a NAT session for a
particular policy rule is used. A value of 0 means that no
NAT session is allocated for this policy rule. A value
other than 0 refers to the NAT session."
::= { midcomResourceEntry 8 }
midcomRscNatSessionId2 OBJECT-TYPE
SYNTAX MidcomNatSessionIdOrZero
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"This object refers to the second allocated NAT session for
this policy rule. MIDCOM-MIB implementations can read this
object to learn whether or not a NAT session for a
particular policy rule is used. A value of 0 means that no
NAT session is allocated for this policy rule. A value
other than 0 refers to the NAT session."
::= { midcomResourceEntry 9 }
midcomRscFirewallRuleId OBJECT-TYPE
SYNTAX Unsigned32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"This object refers to the allocated firewall
rule in the firewall engine for this policy rule.
MIDCOM-MIB implementations can read this value to
learn whether a firewall rule for this particular
policy rule is used or not. A value of 0 means that
no firewall rule is allocated for this policy rule.
A value other than 0 refers to the firewall rule
number within the firewall engine."
::= { midcomResourceEntry 10 }
--
-- Statistics subtree
--
-- The MIDCOM statistics subtree contains a set of managed
-- objects providing statistics about the usage of transaction
-- objects.
--
midcomStatistics OBJECT IDENTIFIER ::= { midcomMonitoring 2 }
midcomCurrentOwners OBJECT-TYPE
SYNTAX Gauge32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The number of different values for midcomRuleOwner
for all current entries in the midcomRuleTable."
::= { midcomStatistics 1 }
midcomTotalRejectedRuleEntries OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The total number of failed attempts to create an entry
in the midcomRuleTable."
::= { midcomStatistics 2 }
midcomCurrentRulesIncomplete OBJECT-TYPE
SYNTAX Gauge32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The current number of policy rules that are incomplete.
Policy rules are loaded via row entries in the
midcomRuleTable. This object counts policy rules that are
loaded but not fully specified, i.e., they are in state
newEntry(1) or setting(2)."
::= { midcomStatistics 3 }
midcomTotalIncorrectReserveRules OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The total number of policy reserve rules that failed
parameter check and entered state incorrectRequest(4)."
::= { midcomStatistics 4 }
midcomTotalRejectedReserveRules OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The total number of policy reserve rules that failed
while being processed and entered state requestRejected(6)."
::= { midcomStatistics 5 }
midcomCurrentActiveReserveRules OBJECT-TYPE
SYNTAX Gauge32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The number of currently active policy reserve rules."
::= { midcomStatistics 6 }
midcomTotalExpiredReserveRules OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The total number of expired policy reserve rules
(entered termination state timedOut(9))."
::= { midcomStatistics 7 }
midcomTotalTerminatedOnRqReserveRules OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The total number of policy reserve rules that were
terminated on request (entered termination state
terminatedOnRequest(10))."
::= { midcomStatistics 8 }
midcomTotalTerminatedReserveRules OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The total number of policy reserve rules that were
terminated, but not on request (entered termination state
terminated(11))."
::= { midcomStatistics 9 }
midcomTotalIncorrectEnableRules OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The total number of policy enable rules that failed
parameter check and entered state incorrectRequest(4)."
::= { midcomStatistics 10 }
midcomTotalRejectedEnableRules OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The total number of policy enable rules that failed
while being processed and entered state requestRejected(6)."
::= { midcomStatistics 11 }
midcomCurrentActiveEnableRules OBJECT-TYPE
SYNTAX Gauge32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The number of currently active policy enable rules."
::= { midcomStatistics 12 }
midcomTotalExpiredEnableRules OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The total number of expired policy enable rules
(entered termination state timedOut(9))."
::= { midcomStatistics 13 }
midcomTotalTerminatedOnRqEnableRules OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The total number of policy enable rules that were
terminated on request (entered termination state
terminatedOnRequest(10))."
::= { midcomStatistics 14 }
midcomTotalTerminatedEnableRules OBJECT-TYPE
SYNTAX Counter32
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The total number of policy enable rules that were
terminated, but not on request (entered termination state
terminated(11))."
::= { midcomStatistics 15 }
--
-- Notifications.
--
midcomUnsolicitedRuleEvent NOTIFICATION-TYPE
OBJECTS { midcomRuleOperStatus, midcomRuleLifetime }
STATUS current
DESCRIPTION
"This notification is generated whenever the value of
midcomRuleOperStatus enters any error state or any
termination state without an explicit trigger by a
MIDCOM client."
::= { midcomNotifications 1 }
midcomSolicitedRuleEvent NOTIFICATION-TYPE
OBJECTS { midcomRuleOperStatus, midcomRuleLifetime }
STATUS current
DESCRIPTION
"This notification is generated whenever the value
of midcomRuleOperStatus enters one of the states
{reserved, enabled, any error state, any termination state}
as a result of a MIDCOM agent writing successfully to
object midcomRuleAdminStatus.
In addition, it is generated when the lifetime of
a rule was changed by successfully writing to object
midcomRuleLifetime."
::= { midcomNotifications 2 }
midcomSolicitedGroupEvent NOTIFICATION-TYPE
OBJECTS { midcomGroupLifetime }
STATUS current
DESCRIPTION
"This notification is generated for indicating that the
lifetime of all member rules of the group was changed by
successfully writing to object midcomGroupLifetime.
Note that this notification is only sent if the lifetime
of a group was changed by successfully writing to object
midcomGroupLifetime. No notification is sent
- if a group's lifetime is changed by writing to object
midcomRuleLifetime of any of its member policies,
- if a group's lifetime expires (in this case,
notifications are sent for all member policies), or
- if the group is terminated by terminating the last
of its member policies without writing to object
midcomGroupLifetime."
::= { midcomNotifications 3 }
--
-- Conformance information
--
midcomCompliances OBJECT IDENTIFIER ::= { midcomConformance 1 }
midcomGroups OBJECT IDENTIFIER ::= { midcomConformance 2 }
--
-- compliance statements
--
-- This is the MIDCOM compliance definition ...
--
midcomCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
"The compliance statement for implementations of the
MIDCOM-MIB module.
Note that compliance with this compliance
statement requires compliance with the
ifCompliance3 MODULE-COMPLIANCE statement of the
IF-MIB [RFC2863]."
MODULE -- this module
MANDATORY-GROUPS {
midcomRuleGroup,
midcomNotificationsGroup,
midcomCapabilitiesGroup,
midcomStatisticsGroup
}
GROUP midcomConfigFirewallGroup
DESCRIPTION
"A compliant implementation does not have to implement
the midcomConfigFirewallGroup."
GROUP midcomResourceGroup
DESCRIPTION
"A compliant implementation does not have to implement
the midcomResourceGroup."
OBJECT midcomRuleInternalIpPrefixLength
MIN-ACCESS read-only
DESCRIPTION
"Write access is not required. When write access is
not supported, return 128 as the value of this object.
A value of 128 means that the function represented by
this option is not supported."
OBJECT midcomRuleExternalIpPrefixLength
MIN-ACCESS read-only
DESCRIPTION
"Write access is not required. When write access is
not supported, return 128 as the value of this object.
A value of 128 means that the function represented by
this option is not supported."
OBJECT midcomRuleMaxIdleTime
MIN-ACCESS read-only
DESCRIPTION
"Write access is not required. When write access is
not supported, return 0 as the value of this object.
A value of 0 means that the function represented by
this option is not supported."
OBJECT midcomRuleInterface
MIN-ACCESS read-only
DESCRIPTION
"Write access is not required."
OBJECT midcomConfigMaxLifetime
MIN-ACCESS read-only
DESCRIPTION
"Write access is not required."
OBJECT midcomConfigPersistentRules
MIN-ACCESS read-only
DESCRIPTION
"Write access is not required."
OBJECT midcomConfigIfEnabled
MIN-ACCESS read-only
DESCRIPTION
"Write access is not required."
OBJECT midcomConfigFirewallGroupId
MIN-ACCESS read-only
DESCRIPTION
"Write access is not required."
OBJECT midcomConfigFirewallPriority
MIN-ACCESS read-only
DESCRIPTION
"Write access is not required."
::= { midcomCompliances 1 }
midcomRuleGroup OBJECT-GROUP
OBJECTS {
midcomRuleAdminStatus,
midcomRuleOperStatus,
midcomRuleStorageType,
midcomRuleStorageTime,
midcomRuleError,
midcomRuleInterface,
midcomRuleFlowDirection,
midcomRuleMaxIdleTime,
midcomRuleTransportProtocol,
midcomRulePortRange,
midcomRuleInternalIpVersion,
midcomRuleExternalIpVersion,
midcomRuleInternalIpAddr,
midcomRuleInternalIpPrefixLength,
midcomRuleInternalPort,
midcomRuleExternalIpAddr,
midcomRuleExternalIpPrefixLength,
midcomRuleExternalPort,
midcomRuleInsideIpAddr,
midcomRuleInsidePort,
midcomRuleOutsideIpAddr,
midcomRuleOutsidePort,
midcomRuleLifetime,
midcomRuleRowStatus,
midcomGroupLifetime
}
STATUS current
DESCRIPTION
"A collection of objects providing information about
policy rules and policy rule groups."
::= { midcomGroups 1 }
midcomCapabilitiesGroup OBJECT-GROUP
OBJECTS {
midcomConfigMaxLifetime,
midcomConfigPersistentRules,
midcomConfigIfBits,
midcomConfigIfEnabled
}
STATUS current
DESCRIPTION
"A collection of objects providing information about
the capabilities of a middlebox."
::= { midcomGroups 2 }
midcomConfigFirewallGroup OBJECT-GROUP
OBJECTS {
midcomConfigFirewallGroupId,
midcomConfigFirewallPriority
}
STATUS current
DESCRIPTION
"A collection of objects providing information about
the firewall rule group and firewall rule priority to
be used by firewalls loaded through MIDCOM."
::= { midcomGroups 3 }
midcomResourceGroup OBJECT-GROUP
OBJECTS {
midcomRscNatInternalAddrBindMode,
midcomRscNatInternalAddrBindId,
midcomRscNatInsideAddrBindMode,
midcomRscNatInsideAddrBindId,
midcomRscNatSessionId1,
midcomRscNatSessionId2,
midcomRscFirewallRuleId
}
STATUS current
DESCRIPTION
"A collection of objects providing information about
the used NAT and firewall resources."
::= { midcomGroups 4 }
midcomStatisticsGroup OBJECT-GROUP
OBJECTS {
midcomCurrentOwners,
midcomTotalRejectedRuleEntries,
midcomCurrentRulesIncomplete,
midcomTotalIncorrectReserveRules,
midcomTotalRejectedReserveRules,
midcomCurrentActiveReserveRules,
midcomTotalExpiredReserveRules,
midcomTotalTerminatedOnRqReserveRules,
midcomTotalTerminatedReserveRules,
midcomTotalIncorrectEnableRules,
midcomTotalRejectedEnableRules,
midcomCurrentActiveEnableRules,
midcomTotalExpiredEnableRules,
midcomTotalTerminatedOnRqEnableRules,
midcomTotalTerminatedEnableRules
}
STATUS current
DESCRIPTION
"A collection of objects providing statistical
information about the MIDCOM server."
::= { midcomGroups 5 }
midcomNotificationsGroup NOTIFICATION-GROUP
NOTIFICATIONS {
midcomUnsolicitedRuleEvent,
midcomSolicitedRuleEvent,
midcomSolicitedGroupEvent
}
STATUS current
DESCRIPTION
"The notifications emitted by the midcomMIB."
::= { midcomGroups 6 }
END
10. Security Considerations
Obviously, securing access to firewall and NAT configuration is
extremely important for maintaining network security. This section
first describes general security issues of the MIDCOM-MIB module and
then discusses three concrete security threats: unauthorized
middlebox configuration, unauthorized access to middlebox
configuration information, and unauthorized access to the MIDCOM
service configuration.
10.1. General Security Issues
There are a number of management objects defined in this MIB module
with a MAX-ACCESS clause of read-write and/or read-create. Such
objects may be considered sensitive or vulnerable in some network
environments. But also access to managed objects with a MAX-ACCESS
clause of read-only may be considered sensitive or vulnerable. The
support for SET and GET operations in a non-secure environment
without proper protection can have a negative effect on network
operations.
SNMP versions prior to SNMPv3 did not include adequate security.
Even if the network itself is secure (for example by using IPsec),
even then, there is no control as to who on the secure network is
allowed to access and GET/SET (read/change/create/delete) the objects
in this MIB module.
Deployment of SNMP versions prior to SNMPv3 is NOT RECOMMENDED.
Compliant MIDCOM-MIB implementations MUST support SNMPv3 security
services including data integrity, identity authentication, data
confidentiality, and replay protection.
It is REQUIRED that the implementations support the security features
as provided by the SNMPv3 framework. Specifically, the use of the
User-based Security Model RFC 3414 [RFC3414] and the View-based
Access Control Model RFC 3415 [RFC3415] is RECOMMENDED.
It is then a customer/operator responsibility to ensure that the SNMP
entity giving access to an instance of this MIB is properly
configured to give access to the objects only to those principals
(users) that have legitimate rights to indeed GET or SET
(change/create/delete) them.
To facilitate the provisioning of access control by a security
administrator using the View-based Access Control Model (VACM)
defined in RFC 3415 [RFC3415] for tables in which multiple users may
need to independently create or modify entries, the initial index is
used as an "owner index". This is supported by the midcomRuleTable
and the midcomGroupTable. Each of them uses midcomRuleOwner as the
initial index. midcomRuleOwner has the syntax of SnmpAdminString,
and can thus be trivially mapped to an SNMP securityName or a
groupName as defined in VACM, in accordance with a security policy.
All entries in the two mentioned tables belonging to a particular
user will have the same value for this initial index. For a given
user's entries in a particular table, the object identifiers for the
information in these entries will have the same subidentifiers
(except for the "column" subidentifier) up to the end of the encoded
owner index. To configure VACM to permit access to this portion of
the table, one would create vacmViewTreeFamilyTable entries with the
value of vacmViewTreeFamilySubtree including the owner index portion,
and vacmViewTreeFamilyMask "wildcarding" the column subidentifier.
More elaborate configurations are possible.
10.2. Unauthorized Middlebox Configuration
The most dangerous threat to network security related to the MIDCOM-
MIB module is unauthorized access to facilities for establishing
policy rules. In such a case, unauthorized principals would write to
the midcomRuleTable for opening firewall pinholes and/or for creating
NAT maps, bindings, and/or sessions. Establishing policies can be
used to gain access to networks and systems that are protected by
firewalls and/or NATs.
If this protection is removed by unauthorized access to MIDCOM-MIB
policies, then the resulting degradation of network security can be
severe. Confidential information protected by a firewall might
become accessible to unauthorized principals, attacks exploiting
security leaks of systems in the protected network might become
possible from external networks, and it might be possible to stop
firewalls blocking denial-of-service attacks.
MIDCOM-MIB implementations MUST provide means for strict
authentication, message integrity check, and write access control to
managed objects that can be used for establishing policy rules.
These are objects in the midcomRuleTable and midcomGroupTable with a
MAX-ACCESS clause of read-write and/or read-create.
Particularly sensitive is write access to the managed object
midcomRuleAdminStatus, because writing it causes policy rules to be
established.
Also, writing to other managed objects in the two tables can make
security vulnerable if it interferes with the authorized
establishment of a policy rule, for example, by wildcarding a policy
rule after the corresponding entry in the midcomRuleTable is created,
but before the authorized owner establishes the rule by writing to
midcomRuleAdminStatus.
Not only unauthorized establishment, but also unauthorized lifetime
extension of an existing policy rule may be considered sensitive or
vulnerable in some network environments. Therefore, means for strict
authentication, message integrity check, and write access control to
managed object midcomGroupLifetime MUST be provided by MIDCOM-MIB
implementations.
10.3. Unauthorized Access to Middlebox Configuration
Another threat to network security is unauthorized access to entries
in the midcomRuleTable. The entries contain information about
existing pinholes in the firewall and/or about the current NAT
configuration. This information can be used for attacking the
internal network from outside. Therefore, a MIDCOM-MIB
implementation MUST also provide means for read access control to the
midcomRuleTable.
Also, a MIDCOM-MIB implementation SHOULD provide means for protecting
different authenticated MIDCOM agents from each other, such that, for
example, an authenticated user can only read entries in the
midcomRuleTable for which the initial index midcomRuleOwner matches
the client's SNMP securityName or VACM groupName.
10.4. Unauthorized Access to MIDCOM Service Configuration
There are three objects with a MAX-ACCESS clause of read-write that
configure the MIDCOM service: midcomConfigIfEnabled,
midcomFirewallGroupId, and midcomFirewallPriority.
Unauthorized writing to object midcomConfigIfEnabled can cause
serious interruptions of network service.
Writing to midcomFirewallGroupId and/or midcomFirewallPriority can be
used to increase or reduce the priority of firewall rules that are
generated when a policy rule is established in the midcomRuleTable.
Increasing the priority might permit firewall rules generated via the
MIDCOM-MIB module to overrule basic security rules at the firewall
that should have higher priority than the ones generated via the
MIDCOM-MIB module.
Therefore, also for these objects, means for strict control of write
access MUST be provided by a MIDCOM-MIB implementation.
11. Acknowledgements
This memo is based on a long history of discussion within the MIDCOM
MIB design team. Many thanks to Mary Barnes, Jeff Case, Wes
Hardaker, David Harrington, and Tom Taylor for fruitful comments and
recommendations and to Juergen Schoenwaelder acting as a very
constructive MIB doctor.
12. IANA Considerations
IANA has assigned an OID for the MIB module in this document:
Descriptor OBJECT IDENTIFIER value
---------- -----------------------
midcomMIB { mib-2 171 }
13. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5189] Stiemerling, M., Quittek, J., and T. Taylor, "Middlebox
Communication (MIDCOM) Protocol Semantics", RFC 5189,
March 2008.
[RFC2578] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
Rose, M. and S. Waldbusser, "Structure of Management
Information Version 2 (SMIv2)", STD 58, RFC 2578, April
1999.
[RFC2579] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
Rose, M. and S. Waldbusser, "Textual Conventions for
SMIv2", STD 58, RFC 2579, April 1999.
[RFC2580] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
Rose, M. and S. Waldbusser, "Conformance Statements for
SMIv2", STD 58, RFC 2580, April 1999.
[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
MIB", RFC 2863, June 2000.
[RFC3411] Harrington, D., Presuhn, R. and B. Wijnen, "An
Architecture for Describing Simple Network Management
Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
December 2002.
[RFC3413] Levi, D., Meyer, P., and B. Stewart, "Simple Network
Management Protocol Applications", STD 62, RFC 3413,
December 2002.
[RFC3414] Blumenthal, U. and B. Wijnen, "User-based Security Model
(USM) for version 3 of the Simple Network Management
Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.
[RFC3418] Presuhn, R., Ed., "Management Information Base (MIB) for
the Simple Network Management Protocol (SNMP)", STD 62,
RFC 3418, December 2002.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[RFC4001] Daniele, M., Haberman, B., Routhier, S., and J.
Schoenwaelder, "Textual Conventions for Internet Network
Addresses", RFC 4001, February 2005.
[RFC4008] Rohit, R., Srisuresh, P., Raghunarayan, R., Pai, N., and
C. Wang, "Definitions of Managed Objects for Network
Address Translators (NAT)", RFC 4008, March 2005.
14. Informative References
[RFC3410] Case, J., Mundy, R., Partain, D. and B. Stewart,
"Introduction and Applicability Statements for Internet-
Standard Management Framework", RFC 3410, December 2002.
[RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and
Issues", RFC 3234, February 2002.
[RFC3303] Srisuresh, P., Kuthan, J., Rosenberg, J., Molitor, A., and
A. Rayhan, "Middlebox communication architecture and
framework", RFC 3303, August 2002.
[RFC3304] Swale, R., Mart, P., Sijben, P., Brim, S., and M. Shore,
"Middlebox Communications (midcom) Protocol Requirements",
RFC 3304, August 2002.
[RFC3415] Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based
Access Control Model (VACM) for the Simple Network
Management Protocol (SNMP)", STD 62, RFC 3415, December
2002.
Authors' Addresses
Juergen Quittek
NEC Europe Ltd.
Kurfuersten-Anlage 36
69115 Heidelberg
Germany
Phone: +49 6221 4342-115
EMail: quittek@nw.neclab.eu
Martin Stiemerling
NEC Europe Ltd.
Kurfuersten-Anlage 36
69115 Heidelberg
Germany
Phone: +49 6221 4342-113
EMail: stiemerling@nw.neclab.eu
Pyda Srisuresh
Kazeon Systems, Inc.
1161 San Antonio Rd.
Mountain View, CA 94043
U.S.A.
Phone: +1 408 836 4773
EMail: srisuresh@yahoo.com
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