| Rfc | 4710 |
|---|
| Title | Real-time Application Quality-of-Service Monitoring (RAQMON)
Framework |
|---|
| Author | A. Siddiqui, D. Romascanu, E. Golovinsky |
|---|
| Date | October 2006 |
|---|
| Format: | TXT, HTML |
|---|
| Status: | PROPOSED STANDARD |
|---|
|
Network Working Group A. Siddiqui
Request for Comments: 4710 D. Romascanu
Category: Standards Track Avaya
E. Golovinsky
Alert Logic
October 2006
Real-time Application Quality-of-Service
Monitoring (RAQMON) Framework
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.
Copyright Notice
Copyright (C) The Internet Society (2006).
Abstract
There is a need to monitor end-devices such as IP phones, pagers,
Instant Messaging clients, mobile phones, and various other handheld
computing devices. This memo extends the remote network monitoring
(RMON) family of specifications to allow real-time quality-of-service
(QoS) monitoring of various applications that run on these devices
and allows this information to be integrated with the RMON family
using the Simple Network Management Protocol (SNMP). This memo
defines the framework, architecture, relevant metrics, and transport
requirements for real-time QoS monitoring of applications.
Table of Contents
1. Introduction ....................................................2
2. RAQMON Functional Architecture ..................................4
3. RAQMON Operation in Congestion-Safe Mode .......................11
4. Measurement Methodology ........................................14
5. Metrics Pre-Defined for the BASIC Part of the RAQMON PDU .......14
6. Report Aggregation and Statistical Data processing .............28
7. Keeping Historical Data and Storage ............................29
8. Security Considerations ........................................30
9. Acknowledgements ...............................................32
10. Normative References ..........................................33
11. Informative References ........................................34
1. Introduction
With the growth of the Internet and advancements in embedded
technologies, smart IP devices (such as IP phones, pagers, instant
message clients, mobile phones, wireless handhelds, and various other
computing devices) have become an integral part of our day-to-day
operations. Enterprise operators, information technology (IT)
managers, application service providers, network service providers,
and so on, need to monitor these application and device types in
order to ensure that end user quality-of-service (QoS) objectives are
met. This memo describes a monitoring solution for these
environments, extending the remote network monitoring (RMON) family
of specifications [RFC2819]. These extensions support real-time QoS
monitoring of typical applications that run on end-devices mentioned
above, and they allow this information to be integrated using the
familiar RMON family of specifications via SNMP [RFC3416].
The Real-time Application QoS Monitoring Framework (RAQMON) allows
end-devices and applications to report QoS statistics in real time.
Many real-time applications (as well as non-real-time applications
managed within the RMON family of specifications) can report
application-level QoS statistics in real time using the RAQMON
Framework outlined in this memo. Some possible applications
scenarios include applications such as Voice over IP, Fax over IP,
Video over IP, Instant Messaging (IM), Email, software download
applications, e-business style transactions, web access from handheld
computing devices, etc.
The user experience of an application running on an IP end-device
depends upon the type of application the user is running and the
surrounding resources available to that application. An end-to-end
application QoS experience is a compound effect of various
application-level transactions and available network and host
resources. For example, the end-to-end user experience of a Voice
over IP (VoIP) call depends on the total time required to set up the
call as much as on media-related performance parameters such as end-
to-end network delay, jitter, packet loss, and the type of codec used
in a call. The performance of a VoIP call is also influenced by
behavior of network protocols like the Reservation Protocol (RSVP),
explicit tags in differentiated services (DiffServ) [RFC2475] or IEEE
802.1 [IEEE802.1D] along with available host resources such as device
CPU or memory utilized by other applications while the call is
ongoing.
The end-to-end application quality of service (QoS) experience is
application context sensitive. For example, the kinds of parameters
reported by an IP telephony application may not really be needed for
other applications such as Instant Messaging. The RAQMON Framework
offers a mechanism to report the end-to-end QoS experience
appropriate for a specific application context by providing
mechanisms to report a subset of metrics from a pre-defined list.
In order to facilitate a complete end-to-end view, RAQMON correlates
statistics that involve:
i. "User, Application, Session"-specific parameters (e.g.,
session setup time, session duration parameters based on
application context).
ii. "IP end-device"-specific parameters during a session (e.g.,
CPU usage, memory usage).
iii. "Transport network"-specific parameters during a session
(e.g., end-to-end delay, one-way delay, jitter, packet loss
etc).
At any given point, the applications at these devices can correlate
such diverse data and report end-to-end performance. The RAQMON
Framework specified in this memo offers a mechanism to report such
end-to-end QoS view and integrate such a view into the RMON family of
specifications. In particular, the RAQMON Framework specifies the
following:
a. A set of basic metrics sent as reports between the RAQMON
entities using for transport existing Internet Protocols such
as TCP or SNMP.
b. Requirements to be met by the underlying transport protocols
that carry the RAQMON reports.
c. A portion of the Management Information Base (MIB) as an
extension of the RMON MIB Modules for use with network
management protocols in the Internet community.
This memo provides the RAQMON functional architecture, RAQMON entity
definitions and requirements, requirements for the transport
protocols, a set of metrics, and an information model for the RAQMON
reports.
Supplementary memos will describe the mapping of the basic RAQMON
metrics onto different transport protocols. For example, the RAQMON
PDU [RFC4712] memo provides definitions of syntactical PDU structure
and use case scenarios of transmission of such PDUs over the
Transmission Control Protocol (TCP) and the Simple Network Management
Protocol (SNMP).
The RAQMON MIB [RFC4711] memo describes the Management Information
Base (MIB) for use with the SNMP protocol in the Internet community.
The document proposes an extension to the Remote Monitoring MIB
[RFC2819] to accommodate RAQMON solutions.
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 [RFC2119].
2. RAQMON Functional Architecture
The RAQMON Framework extends the architecture created in the RMON MIB
[RFC2819] by providing application performance information as
experienced by end-users. The RAQMON architecture is based on three
functional components named below:
- RAQMON Data Source (RDS)
- RAQMON Report Collector (RRC)
- RAQMON MIB Structure
A RAQMON Data Source (RDS) is a functional component that acts as a
source of data for monitoring purposes. End-devices like IP phones,
cell phones, and pagers, and application clients like instant
messaging clients, soft phones in PCs, etc., are envisioned to act as
RDSs within the RAQMON Framework.
+----------------------+ +---------------------------+
| IP End-Device | | IP End-Device >----+ |
|+--------------------+| |+--------------------+ | |
|| APPLICATION || || APPLICATION | | |
|| -Voice over IP <----(1)----> -Voice over IP >- + | |
|| -Instant Messaging|| || -Instant Messaging| | 3 |
|| -Email || || -Email | 2 | |
|+--------------------+| |+--------------------+ | | |
| | | | | |
| | | +------------------+ | | |
+----------------------+ | |RAQMON Data Source|<-+ | |
| | (RDS) |<---+ |
| +------------------+ |
+-----------|---------------+
|
(4) RAQMON PDU transported
over TCP or SNMP Notifications
|
+----------------------------+
| |
|/ |/
+------------------+ +------------------+ +------------+
|RAQMON Report | .. |RAQMON Report | | Management |
|Collector (RRC) #n| |Collector (RRC) #1|<--5-->| Application|
+------------------+ +------------------+ +------------+
Figure 1 - RAQMON Framework.
(1) Communication Session between real-time applications
(2) Context-Sensitive Metrics
(3) Device State Specific Metrics
(4) Reporting session - RAQMON metrics transmitted over specified
interfaces (Specific Protocol Interface, IP Address, port)
(5) Management Application - RRC interaction using the RAQMON MIB
A RAQMON Report Collector (RRC) collects statistics from multiple
RDSs, analyzes them, and stores such information appropriately. RRC
is envisioned to be a network server, serving an administrative
domain defined by the network administrator. The RRC component of
the RAQMON architecture is envisioned to be computationally
resourceful. Only RRCs should implement the RAQMON MIB module.
The RAQMON Management Information Base (RAQMON MIB) extends the
Remote Monitoring MIB [RFC2819] to accommodate the RAQMON Framework
and exposes End-to-End Application QoS information to Network
Management Applications.
2.1. RAQMON Data Source (RDS)
2.1.1. RAQMON Data Source (RDS) Functional Architecture
A RAQMON Data Source (RDS) is a source of data for monitoring
purposes. The RDS monitoring function is performed in real time
during communication sessions. The RDS entities capture QoS
attributes of such communication sessions and report them within a
RAQMON "reporting session".
An RDS is primarily responsible for abstracting IP end-devices and
applications within the RAQMON architecture. It gathers the
parameters for a particular communication session and forwards them
to the appropriate RAQMON Report Collector (RRC). Since it is
envisioned that the RDS functionality will be realized by writing
firmware/software running on potentially small, low-powered end-
devices, the design of the RDS element is optimized towards that end.
Like the implementations of routing and management protocols, an
implementation of RDS in an end-device will typically execute in the
background, not in the data-forwarding path.
RDSs use a PUSH mechanism to report QoS parameters. While the
applications running on the RDS decide about the content of the PDU
appropriate for an application context, an RDS asynchronously sends
out reports to RRC.
The rate at which PDUs are sent from RDSs to RRCs is controlled by
the applications' administrative domain policy. While this mechanism
provides flexibility to gather a detailed end-to-end experience
required by IT managers and system administrators, certain steps
should be followed to operate RAQMON in congestion-safe manner.
Section 3 addresses steps required for congestion-safe operation.
An RDS reports QoS statistics for simplex flows. At a given
instance, a report from RDS is logically viewed as a collection of
QoS parameters associated with a communication session as perceived
by the reporting RDS. For example, if two IP phone users, Alice and
John, are involved in a communication session, the end-to-end delay
experienced by the IP phone user Alice could be different from the
one experienced by the IP phone user John for a variety of reasons.
Hence, a report from Alice's IP phone represents the QoS performance
of that call as perceived by the RDS that resides in Alice's IP
phone.
2.1.2. RAQMON Data Source (RDS) Requirements
1. RAQMON Data Sources SHALL gather reports from multiple
applications residing in that device and SHALL send out
compound QoS reports associated with multiple communication
sessions at a given moment.
Examples include a conference bridge hosting several different
conference calls or a two-party video call consisting of
audio/video sessions. In each case an RDS could send out one
single RAQMON report that consists of multiple sub-reports
associated with audio and video sessions or sub-reports for
each conference call.
2. RAQMON Data Sources MUST implement the TCP transport and MAY
implement the SNMP transport.
2.1.3. Configuring RAQMON Data Sources
In order to report statistics to RAQMON Report Collectors, RDSs will
need to be configured with the following parameters:
1. The time interval between RAQMON PDUs. This parameter MUST be
configured such that overflow of any RAQMON parameter within a
PDU between consecutive transmissions is avoided.
2. The IP address and port of target RRC.
An RDS may use manual configuration for the RDS configuration
parameters using command line interface (CLI), Telephone User
Interface (TUI), etc.
One of the following mechanisms to gain access to configuration
parameters can also be considered:
- RDS acts as a trivial file transfer protocol (TFTP) client and
downloads text scripts to read the parameters.
- RDS acts as a Dynamic Host Configuration Protocol (DHCP) Client
and gets RRC addressing information as a DHCP option.
- RDS acts as a DNS client and gets target collector information
from a DNS Server.
- RDS acts as a LDAP Client and uses directory look-ups.
Identifying the DHCP option and structure to use, defining the
structure of the configuration information in DNS, or defining a LDAP
schema could be explored as items of future work.
Compliance to the RAQMON specification does not require usage of any
specific configuration mechanisms mentioned above. It is left to the
implementers to choose appropriate provisioning mechanisms for a
system.
2.2. RAQMON Report Collector (RRC)
2.2.1. RAQMON Report Collector (RRC) Functional Architecture
A RAQMON Report Collector (RRC) receives RAQMON PDUs from multiple
RDSs and analyzes and stores the information in the RAQMON MIB. The
RRC is envisioned to be computationally resourceful, providing a
storage and aggregation point for a set of RDSs.
Since RDSs can belong to separate administrative domains, the RAQMON
Framework allows RDSs to report QoS parameters to separate RRCs.
Vendors can develop a management application to correlate information
residing in different RRCs across multiple administrative domains to
represent one communication session. However, such an application-
level specification is beyond the scope of this memo.
2.2.2. RAQMON Report Collector (RRC) Requirements
1. RAQMON Report Collectors MUST support the mandatory mapping
over TCP of the RAQMON information model defined in [RFC4712]
with the purpose of receiving RAQMON reports from RAQMON Data
Sources (RDS).
2. RAQMON Report Collectors MAY support the optional mapping over
SNMP notifications of the RAQMON information model defined in
[RFC4712].
3. RAQMON Report Collectors MUST implement session timeout
mechanisms to assume end of reporting for RDSs that have been
out of reporting for a reasonable duration of time. Such
timeout parameters SHOULD be configurable in vendor
implementations, as programmable parameters at deployment.
4. RAQMON Report Collectors MUST support the RAQMON-MIB module and
meet the compliance requirements of the raqmonCompliance
MODULE-COMPLIANCE definition as described in [RFC4711]. The
population of the RAQMON MIB with performance monitoring
information is independent of the transport protocol, or
protocols used to carry the information between RDSs and RRCs.
2.3. Information Model and RAQMON Protocol Data Unit (PDU)
2.3.1. RAQMON Information Model
RAQMON defines a set of basic metrics that characterize the QoS of
applications, as reported by RAQMON Data Sources. This basic set of
metrics is defined in Section 5 of this memo. There is no minimal
requirement for a mandatory set of metrics to be supported by an RDS.
Specific applications, new types of network appliances or new methods
to measure and characterize the QoS of applications lead to the
requirement for the information model to be extensible. To answer
this need, the information model is designed so that vendors can
extend it by adding new metrics.
Although NOT REQUIRED for RAQMON conformance, extensions of the
information model can offer useful information for specific
applications. An example of metrics that can extend the basic RAQMON
information model are the detailed metrics for VoIP media monitoring
and call quality included in the VoIP Metrics Report Block defined in
[RFC3611].
The RAQMON Information model is expressed by defining a conceptual
RAQMON Protocol Data Unit (PDU).
2.3.2. RAQMON Protocol Data Unit
A RAQMON Protocol Data Unit (PDU) is a common data format understood
by RDSs and RRCs. A RAQMON PDU does not transport application data
but rather occupies the place of a payload specification at the
application layer of the protocol stack. Different transport
mappings may be used to carry RAQMON PDU between RDSs and RRCs.
Transport protocol requirements are being defined in Section 2.4 of
this memo.
Though architected conceptually as a single PDU, the RAQMON PDU is
functionally divided into two different parts. They are the BASIC
part, and the Application-Specific Extensions, required for
application-, vendor-, and device-specific extensions.
The BASIC part of the RAQMON PDU:
The BASIC part of the RAQMON PDU follows the SMI Network
Management Private Enterprise Code 0, indicating an IETF standard
construct. The RAQMON PDU BASIC part offers an entry-type from a
pre-defined list of QoS parameters defined in Section 5 and allows
applications to fill in appropriate values for those parameters.
Application developers also have the flexibility to make an RDS
report built only of a subset of the parameters listed in
Section 5. There is no need to carry all metrics in every PDU;
moreover, it is RECOMMENDED that static or pseudo-static metrics
that do not change or seldom change for a given session or
application will be send only when the session or application are
initiated, and then at large time intervals.
The Application part of RAQMON PDU:
Since it is difficult to structure a BASIC part that meets the
needs of all applications, RAQMON provides extension capabilities
to convey application-, vendor-, and device-specific parameters
for future use. Additional parameters can be defined within
payload of the APP part of the PDU by the application developers
or vendors. The owner of the definition of the application part
of the RAQMON PDU is indicated by a vendor's SMI Network
Management Private Enterprise Code defined in
http://www.iana.org/assignments/enterprise-numbers. Such
application-specific extensions should be maintained and published
by the application vendor.
Though RDSs and RRCs are designed to be stateless for an entire
reporting session, the framework requires an indication for the end
of the reporting. For this purpose, an RDS MUST send a RAQMON NULL
PDU. A NULL PDU is a RAQMON PDU containing ALL NULL values (i.e.,
nothing to report).
2.4. RDS/RRC Network Transport Protocol Requirements
The RAQMON PDUs rely on the underlying protocol(s) to provide
transport functionalities and other attributes of a transport
protocol, e.g., transport reliability, re-transmission, error
correction, length indication, congestion safety,
fragmentation/defragmentation, etc. The maximum length of the RAQMON
data packet is limited only by the underlying protocols.
The following requirements MUST be met by the transport protocols:
1. The transport protocol SHOULD allow for RDS lightweight
implementations. RDSs will be implemented on low-powered
embedded devices with limited device resources.
2. Scalability - Since RRCs need to interact with a very large
number (many tens, many hundreds, or more) of RDSs, scalability
of the transport protocol is REQUIRED.
3. Congestion safety - as per [RFC2914]. See also Section 3.
4. Security - Since RAQMON statistics may carry sensitive system
information requiring protection from unauthorized disclosure
and modification in transit, a transport protocol that provides
strong secure modes or allows for data encryption and integrity
to be applied is REQUIRED.
5. NAT-Friendly - The transport protocol SHOULD comply with
[RFC3235], so that an RDS could communicate with an RRC through
a Firewall/Network Address Translation device.
6. The transport protocol MAY implement session timeout mechanisms
to assume end of reporting for RDSs that have been out of
reporting for a reasonable duration of time. Such timeout
parameters SHOULD be configurable in vendor implementations,
programmable at deployment.
7. Reliability - The RAQMON Framework expects PDUs to operate in
lossy networks. However, retransmission is not included in the
RAQMON framework, in order to keep the design simple. If
retransmission is a necessity, RAQMON MAY operate over
transport protocols, such as TCP.
In the future, if RAQMON PDUs are to be carried in an underlying
protocol that provides the abstraction of a continuous octet stream
rather than messages (packets), an encapsulation for the RAQMON
packets must be defined to provide a framing mechanism. Framing is
also needed if the underlying protocol contains padding so that the
extent of the RAQMON payload cannot be determined. No framing
mechanism is defined in this document. Carrying several RAQMON
packets in one network or transport packet reduces header overhead.
Further memos like [RFC4712] describe how the PDU is transported over
existing protocols like the Transmission Control Protocol (TCP) or
the Simple Network Management Protocol (SNMP).
3. RAQMON Operation in Congestion-Safe Mode
RAQMON PDUs can be transmitted over multiple transport protocols.
The RAQMON Framework will be congestion safe, if a RAQMON PDU is
transported over TCP.
One solution to the congestion awareness problem could have been to
discourage the use of UDP entirely for RAQMON. Though RAQMON PDUs
can be transported over TCP, some transports like SNMP over TCP are
not commonly practiced in practical deployments.
The use of UDP inherently increases the risks of network congestion
problems, as UDP itself does not define congestion prevention,
avoidance, detection, or correction mechanisms. The fundamental
problem with UDP is that it provides no feedback mechanism to allow a
sender to pace its transmissions against the real performance of the
network. While this tends to have no significant effect on extremely
low-volume sender-receiver pairs, the impact of high-volume
relationships on the network can be severe. This problem could be
further aggravated by large RAQMON PDUs fragmented at the UDP level.
Transport protocols such as DCCP can also be used as underlying
RAQMON PDU transport, which provides flexibility of UDP style
datagram transmission with congestion control.
It should be noted that the congestion problem is not just between
RDS and RRC pairs, but whenever there is a high fan-in ratio,
congestion could occur (e.g., many RDSs reporting to an RRC). Within
the RAQMON Framework using UDP as a transport, congestion safety can
be achieved in following ways:
1. Constant Transmission Rate: In a well-managed network, a
constant transmission rate policy (e.g., 1 RAQMON PDU per
device every N seconds) will ensure congestion safety as
devices are introduced into the network in a controlled manner.
For example, in an enterprise network, IP Phones are added in a
controlled manner, and a constant transmission rate policy can
be sufficient to ensure congestion-safe operation. The
configured rate needs to be related to the expected peak number
of devices. As a worst-case scenario, if the RDSs enforce an
administrative policy where the maximum PDU transmission rate
is no more than one RAQMON PDU every two minutes, a UDP-based
implementation can be as congestion safe as a TCP-based
implementation. Such policies can be enforced while
configuring RDSs, and the timers for the constant rate need to
be randomly jittered.
2. Single outstanding requests: This approach requires that a
request be sent at the application level, then there is a wait
for some sort of response indicating that the request was
received before sending anything else. This produces an effect
described by some as "ping-ponging": traffic bounces back and
forth between two nodes like a ping-pong ball in a match.
Since there's only one ball in play between any two players at
any given time, most of the potential for congestion cascades
is eliminated. For reliability and efficiency reasons, this
technique must include backed-off retransmissions. For
example, if RAQMON PDUs are transported using SNMP INFORM PDUs
over UDP, a SNMP response from the RRC SHOULD be processed by
the RDS to implement this mechanism. [RFC4712] specifies that
if the SNMP notifications transport mapping mechanism is
implemented, it is RECOMMENDED to use INFORM PDUs, and it is
NOT RECOMMENDED to use Trap PDUs.
This pacing or serialization approach has the side-effect of
significantly reducing the maximum throughput, as transmission
occurs in only one direction at a time and there is at least a
2xRTT (round-trip time) delay between transmissions. More
sophisticated algorithms (such as those in TCP and Stream
Control Transmission Protocol (SCTP)) have been developed to
address this, and it would be inappropriate to duplicate that
work at the application level. Consequently, if greater
efficiency is required than that provided by this simple
approach, implementers SHOULD use TCP, SCTP, or another such
protocol. But if one absolutely must use UDP, this approach
works. It has been also used in other application scenarios
like SIP over UDP.
3. By restricting transmission to a maximum transmission unit
(MTU) size: An RDS may be faced with a request to deliver a
large message using UDP as a transport. Fragmentation of such
messages is problematic in several ways. Loss of any fragment
requires time-out and retransmission of the message. The
fragments are commonly transmitted out of the interface at
local interface (usually LAN) rates, without awareness of the
intervening network conditions. For these reasons, it is
generally considered a bad practice to send large PDUs over
UDP. If the MTU size is known, as an implementation, an RDS
should not allow an application to send more information by
limiting the size of transmissions over UDP to reduce the
effects of fragmentation. As an alternate, an RDS MAY also
send parameters to RRC over multiple RAQMON PDUs but identify
them as part of the same RAQMON reporting session with exactly
the same Network Time Protocol (NTP) [RFC1305] time stamp.
While the actual MTU of a link may not be known, common
practice seems to indicate that the RDS local interface MTU is
likely to be a reasonable "approximation". Where the actual
path MTU is known, that value SHOULD be used instead.
4. Irrespective of choice of transport protocol, it is also
RECOMMENDED that no more than 10% network bandwidth be used for
RDS/RRC reporting. More frequent reports from an RDS to RRC
would imply requirements for higher network bandwidth usage.
4. Measurement Methodology
It is not the intent of this document to recommend a methodology to
measure any of the QoS parameters defined in Section 5. Measurement
algorithms are left to the implementers and equipment vendors to
choose. There are many different measurement methodologies available
for measuring application performance. These include probe-based,
client-based, synthetic-transaction, and other approaches. This
specification does not mandate a particular methodology and is open
to any methodology that meets the minimum requirements. For
conformance to this specification, it is REQUIRED that the collected
data match the semantics described herein. However, it is
RECOMMENDED that vendors use IETF-defined and International
Telecommunication Union (ITU)-specified methodologies to measure
parameters when possible.
5. Metrics Pre-Defined for the BASIC Part of the RAQMON PDU
The BASIC part of the RAQMON PDU provides for a list of pre-defined
parameters frequently used by applications to characterize end-to-end
application Quality of Service. This section defines a set of simple
metrics to be contained in the BASIC part of the RAQMON PDU, through
reference to existing IETF, ITU, and other standards organizations'
documents. Appropriate IETF or ITU references are included in the
metrics definitions.
As mentioned earlier, the RAQMON PDU also contains an application-
specific part, where application- and vendor-specific information not
included in BASIC part can be added as <Name, Value> pairs, or as a
variable binding list. These extensions, managed independently by
vendors or other organizations, should be published for wider
interoperability.
Applications are not required to report all the parameters mentioned
in this section, but should have the flexibility to report a subset
of these parameters appropriate to an application context. The memo
further identifies the parameters that RDSs are required to include
in all PDUs for compliance, as well as optional parameters that RDSs
may report as needed. The definitions presented here are meant to
provide guidance to implementers, and IETF metric definition
references are provided for each metric. Application developers
should choose the metrics appropriate to their applications' needs.
Syntactical representations of the parameters identified here are
provided in the [RFC4712] specification.
5.1. Data Source Address (DA)
The Data Source Address (DA) is the address of the data source. This
could be either a globally unique IPv4 or IPv6 address, or a
privately IPv4 allocated address as defined in [RFC1918].
It is expected that the DA would remain constant within a given
communication session. RDSs SHOULD avoid sending these parameters
within RAQMON reports too often to ensure an efficient usage of
network resources.
5.2. Receiver Address (RA)
The Receiver Address (RA) takes the same form as the Data Source
Address (DA) but represents the Receiver's Address. In a
communication session, the reporting RDSs SHOULD fill in the other
party's address as a Receiver Address. Like the Data Source Address,
this could be either a globally unique IPv4 or IPv6 address, or a
privately allocated IPv4 address as defined in [RFC1918].
It is expected that the Receiver Address (RA) would remain constant
within a given communication session. RDSs SHOULD avoid sending
these parameters within RAQMON reports too often in order to ensure
an efficient usage of network resources.
5.3. Data Source Name (DN)
The Data Source Name (DN) item could be of various formats as needed
by the application. Forms the DN could take include, but are not
restricted to:
- "user@host", or "host" if a user name is not available as on
single-user systems. For both of these formats, "host" is the
fully qualified domain name of the host from which the payload
originates, formatted according to the rules specified in
[RFC1034], [RFC1035], and Section 2.1 of [RFC1123]. Use example
names are "big-guy@example.com" or "big-guy@192.0.2.178" for a
multi-user system. On a system with no user name, an example
would be "ip-phone4630.example.com". It is RECOMMENDED that the
standard host's numeric address not be reported via the DN
parameter, as the DA parameter is used for that purpose.
- Another instance of a DN could be a valid E.164 phone number, a
SIP URI, or any other form of telephone or pager number. The
phone number SHOULD be formatted with a plus sign replacing the
international access code. Example: "+44-116-496-0348" for a
number in the UK.
The DN value is expected to remain constant for the duration of a
session. RDSs SHOULD avoid sending these parameters within RAQMON
reports too often in order to ensure an efficient usage of network
resources.
5.4. Receiver Name (RN)
The Receiver Name (RN) takes the same form as DN, but represents the
Receiver's name. In a communication session, an application SHOULD
supply as an RN the name of the other party with which it is
communicating.
The RN value is expected to remain constant for the duration of a
session. RDSs SHOULD avoid sending these parameters within RAQMON
reports too often in order to ensure an efficient usage of network
resources.
5.5. Data Source Device Port Used
This parameter indicates the source port used by the application for
a particular session or sub-session in communication. Examples of
ports include TCP Ports or UDP Ports, as used by communication
application protocols such as Session Initiation Protocol (SIP), SIP
for Instant Messaging and Presence Leveraging Extensions (SIMPLE),
H.323, RTP, HyperText Transport Protocol (HTTP), and so on.
This parameter MUST be sent in the first RAQMON PDU.
5.6. Receiver Device Port Used
This parameter indicates the receiver port used by the application
for a particular session or sub-session. Examples of ports include
TCP Ports, or UDP Ports used by communication application protocols
such as SIP, SIMPLE, H.323, RTP, HTTP, etc.
This parameter MUST be sent in the first RAQMON PDU.
5.7. Session Setup Date/Time
This parameter gives the time when the setup was initiated, if the
application has a setup phase, or when the session was started, if
such a setup phase does not exist. The time is represented using the
timestamp format of the Network Time Protocol (NTP), which is in
seconds relative to 0h UTC (Coordinated Universal Time) on 1 January
1900 [RFC1305].
This parameter SHOULD be sent only in the first RAQMON PDU, after the
session setup is completed.
5.8. Session Setup Delay
The Session Setup Delay metric reports the time taken from an
origination request being initiated by a host/endpoint to the media
path being established (or a session progress indication being
received from the remote host/endpoint), expressed in milliseconds.
For example, in VoIP systems, a session setup time can be measured as
the interval from the last DTMF (dual-tone multi-frequency) button
pushed to the first ring-back tone that indicates that the far end is
ringing. Another example would be the Session Setup Delay of a SIP
call, which is measured as the elapsed time between when an INVITE is
generated by a User Agent and when the 200 OK is received.
This parameter SHOULD be sent only in the first RAQMON PDU, after the
session setup is completed.
5.9. Session Duration
The Session Duration metric reports how long a session or a sub-
session lasted. This metric is application context sensitive. For
example, a VoIP Call Session Duration can be measured as the elapsed
time between call pickup and call termination, including session
setup time.
This parameter SHOULD be sent only in the first RAQMON PDU, after the
session is terminated.
5.10. Session Setup Status
The Session Setup Status metric is intended to report the
communication status of a session. Its values identify appropriate
communication session states, such as Call Progressing, Call
Established successfully, "trying", "ringing", "re-trying", "RSVP
reservation failed", and so on.
Session setup status is meaningful in the context of applications.
For this reason, applications SHOULD use this metric together with
the application/name metrics defined in Section 5.32.
This information could be used by network management systems to
calculate parameters such as call success rate, call failure rate,
etc., or by a debugging tool that captures the status of a call's
setup phase as soon as a call is established.
This parameter SHOULD be sent after each change in the session
status.
5.11. Round-Trip End-to-End Network Delay
The Round-Trip End-to-End Network Delay, defined in [RFC3550] for
applications running over RTP and in [RFC2681] for all other IP
applications, is a key metric for Application QoS Monitoring. Some
applications do not perform well (or at all) if the end-to-end delay
between hosts is large relative to some threshold value. Erratic
variation in delay values makes it difficult (or impossible) to
support many real-time applications such as Voice over IP, Video over
IP, Fax over IP etc.
The Round-Trip End-to-End Network delay of the underlying transport
network is measured using methodologies described in [RFC3550] for
RTP and in [RFC2681] for other IP applications.
Note that the packets used for measurement in some methodologies may
be of a different type from those used for media (e.g., ICMP instead
of RTP) and hence may differ in terms of route and queue priority.
This may result in measured delays being different from those
experienced on the media path. Conformance for this metric requires
that actual application packets, or packets of the same application
type, be used.
Support for RTP can be determined by the support of the RTP MIB
[RFC2959] in the hosts running the applications or by inclusion of
the string 'RTP' at the beginning of the Application Name (Section
5.32).
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.12. One-Way End-to-End Network Delay
The One-Way End-to-End Network Delay [RFC2679] metric reports the
One-Way End-to-End delay encountered by traffic from the source to
the destination network interface. One-Way Delay measurements
identified by the IP Performance Metrics (IPPM) Working Group
[RFC2679] will be used to measure one-way end-to-end network delay.
The need for such a metric is derived from the fact that the path
from a source to a destination may be different from the path from
the destination back to the source ("asymmetric paths"), such that
different sequences of routers are used for the forward and reverse
paths. Therefore, round-trip measurements actually measure the
performance of two distinct paths together.
Measuring each path independently highlights the performance
difference between the two paths that may traverse different Internet
service providers, and even radically different types of networks
(for example, research versus commodity networks, or ATM
(Asynchronous Transfer Mode) versus Packet-over-SONET (Synchronous
Optical) transport networks).
Even when the two paths are symmetric, they may have radically
different performance characteristics due to asymmetric queuing.
Performance of an application may depend mostly on the performance in
one direction. For example, a file transfer using TCP may depend
more on the performance in the direction that data flows than on the
direction in which acknowledgements travel.
In QoS-enabled networks, provisioning in one direction may be
radically different from provisioning in the reverse direction, and
thus the QoS guarantees differ. Measuring the paths independently
allows the verification of both guarantees.
RAQMON SHOULD NOT derive One-Way End-to-End Network Delay by assuming
Internet paths are symmetric (i.e., dividing Round-Trip Delay by
two).
Note that the packets used for measurement in some methodologies may
be of a different type from those used for media (e.g., ICMP instead
of RTP) and hence may differ in terms of route and queue priority.
This may result in measured delays being different from those
experienced on the media path. Conformance for this metric requires
that actual application packets, or packets of the same application
type, be used.
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.13. Application Delay
Various Network Delay versions, as outlined in Sections 5.11 and
5.12, do not include delays associated with buffering, play-out,
packet-sequencing, coding/decoding, etc., in the end-devices. The
Application Delay metric defined in this section is targeted to
capture all such delay parameters, providing a total application
endpoint delay.
Application delay can be expressed as the time delay introduced
between the network interface and the application-level presentation.
Since it is difficult to envision usage of all sorts of applications,
the following guidance is provided to the implementers to measure the
application delay:
- The sending end contribution to application delay is defined as the
sum of sample sequencing, accumulation, and encoding delay.
- The receiving end contribution to application delay is calculated
as the sum of delays associated with buffering, play-out, packet-
sequencing, and decoding associated with the receiving direction,
if relevant.
The endpoint application delay is defined as the sum of the receiving
and sending contributions to delay measured or estimated within the
endpoint that is generating this report.
It is easy to recognize that applications running on an IP device can
experience same network delay but have different application-
associated delay values. As such, the user experience associated
with specific applications may vary while the network delay value
remains same for both the applications.
Having network delay and application delay measurements available, a
management application can represent the delay experienced by the end
user at the application level as a sum of network delay and the
application delays reported from the endpoints. However, the
specification of such a management application is outside the scope
of the RAQMON specification.
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.14. Inter-Arrival Jitter
The Inter-Arrival Jitter metric provides a short-term measure of
network congestion [RFC3550]. The jitter measure may indicate
congestion before it leads to packet loss. The inter-arrival jitter
field is only a snapshot of the jitter at the time when a RAQMON PDU
is generated and is not intended to be taken quantitatively as
indicated in [RFC3550]. Rather, it is intended for comparison of
inter-arrival jitter from one receiver over time. Such inter-arrival
jitter information is extremely useful to understand the behavior of
certain applications such as Voice over IP, Video over IP, etc.
Inter-arrival jitter information is also used in the sizing of play-
out buffers for applications requiring the regular delivery of
packets (for example, voice or video play-out).
In [RFC3550], the selection function is implicitly applied to
consecutive packet pairs, and the "jitter estimate" is computed by
applying an exponential filter with parameter 1/16 to generate the
estimate (i.e., j_new = 15/16* j_old + 1/16*j_new).
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.15. IP Packet Delay Variation
[RFC3393] provides guidance to several absolute jitter parameters.
RAQMON uses the [RFC3393] definition of the IP Packet Delay Variation
(ipdv) for packets inside a stream of packets. The IP Delay
Variation metric is used to determine the dynamics of queues within a
network (or router) where the changes in delay variation can be
linked to changes in the queue length processes at a given link or a
combination of links. Such a parameter provides visibility within an
IP Network and a better understanding of application-level
performance problems as it relates to IP Network performance.
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.16. Total Number of Application Packets Received
This metric reports the number of application payload packets
received by the RDS as part of this session since the last RAQMON PDU
was sent up until the time this RAQMON PDU was generated.
This parameter represents a very simple incremental counter that
counts the number of "application" packets that an RDS has received.
Application packets MAY include signaling packets. Since this count
is a snapshot in time, depending on application type, it also varies
based on the application states, e.g., an RDS within an application
session will report the aggregated number of application packets that
were sent out during signaling setup, media packets received, session
termination, etc.
For example, during Voice over IP or Video over IP sessions setup,
this counter represents the number of signaling-session-related
packets that have been received that will be derived from the
relevant application signaling protocol stack such as SIP or H.323,
SIMPLE, and various other signaling protocols used by the application
to establish the communication session.
However, during a period when media is established between the
communicating entities, this counter will be indicative of the number
of RTP Frames that have been sent out to the communicating party
since last PDU was sent out. The methodology described within RTCP
SR/RR reports [RFC3550] to count RTP frames will be applied wherever
applications use RTP. This being a cumulative counter, applications
need to take into consideration the possibility of the counter
overflowing and restarting counting from zero.
Support for RTP can be determined by the support of the RTP MIB
[RFC2959] in the hosts running the applications or by inclusion of
the string 'RTP' at the beginning of the Application Name (Section
5.32).
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.17. Total Number of Application Packets Sent
This metric reports the number of signaling and payload packets sent
by the RDS as part of this session since the last RAQMON PDU was sent
until the time this RAQMON PDU was generated. Applications packets
MAY include signaling packets. Similar to the total number of
application packets received parameter in Section 5.16, this count is
a snapshot in time. Depending on the application type, the counter
also varies based on various application states, including packet
counts for signaling setup, media establishment, session termination
states, and so on. This being a cumulative counter, applications
need to take into consideration the possibility of the counter
overflowing and restarting counting from zero.
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.18. Total Number of Application Octets Received
This metric reports the total number of signaling and payload octets
received in packets by the RDS as part of this session since the last
RAQMON PDU was sent, up until the time this RAQMON packet was
generated. Applications octets MAY include signaling octets. The
methodology described by [RFC3550] will be applied wherever
applications use RTP. This being a cumulative counter, applications
need to take into consideration the possibility of the counter
overflowing and restarting counting from zero.
Support for RTP can be determined by the support of the RTP MIB
[RFC2959] in the hosts running the applications or by inclusion of
the string 'RTP' at the beginning of the Application Name (Section
5.32).
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.19. Total Number of Application Octets Sent
This metric reports the total number of signaling and payload octets
received in packets by the RDS as part of this session since the last
RAQMON PDU was sent, up until the time this RAQMON packet was
generated. This is similar to the Total Number of Application Octets
Received metric. Applications octets MAY include signaling octets.
The methodology described by [RFC3550] will be applied wherever
applications use RTP. This being a cumulative counter, applications
need to take into consideration the possibility of the counter
overflowing and restarting counting from zero.
Support for RTP can be determined by the support of the RTP MIB
[RFC2959] in the hosts running the applications or by inclusion of
the string 'RTP' at the beginning of the Application Name (Section
5.32).
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.20. Cumulative Packet Loss
The cumulative packet loss metric indicates the loss associated with
the network as well as local device losses over time. This parameter
is counted as the total number of application packets from the source
that have been lost since the beginning of the session. This number
is defined to be the number of packets expected less the number of
packets actually received, where the number of packets received
includes the count of packets that are late or duplicates. If a
packet is discarded due to late arrival, then it MUST be counted as
either lost or discarded but MUST NOT be counted as both.
Packet loss by the underlying transport network SHALL be measured
using the methodologies described in [RFC3550] for RTP traffic and
[RFC2680] for other IP traffic. The number of packets expected is
defined to be the extended last sequence number received, as defined
next, less the initial sequence number received. For RTP traffic,
this may be calculated using techniques such as those shown in
Appendix A.3 of [RFC3550].
Packet loss by the underlying transport network SHALL be measured
using the methodologies described in [RFC3550] for RTP traffic and
[RFC2680] for other IP traffic. The number of packets expected is
defined to be the extended last sequence number received, as defined
next, less the initial sequence number received. For RTP traffic,
this may be calculated using techniques such as those shown in
Appendix A.3 of [RFC3550].
Support for RTP can be determined by the support of the RTP MIB
[RFC2959] in the hosts running the applications or by inclusion of
the string 'RTP' at the beginning of the Application Name (Section
5.32).
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.21. Packet Loss in Fraction
The Packet Loss in Fraction metric represents the packet loss as
defined above, but expressed as a fraction of the total traffic over
time.
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.22. Cumulative Application Packet Discards
The RAQMON Framework allows applications to distinguish between
packets lost by the network and those discarded due to jitter and
other application-level errors. Though packet loss and discards have
an equal effect on the quality of the application, having separate
counts for packet loss and discards helps identify the source of
quality degradation.
The packet discard metric indicates packets discarded locally by the
device over time. Local device-level packet discard is captured as
the total number of application-level packets from the source that
have been discarded since the beginning of reception, due to late or
early arrival, under-run or overflow at the receiving jitter buffer,
or any other application-specific reasons.
If the RDS cannot tell the difference between discards and lost
packets, then it MUST report only lost packets and MUST NOT report
discards.
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.23. Packet Discards in Fraction
The packet discards in fraction metric represents packets from the
source that have been discarded since the beginning of the reception
but expressed as a fraction of the total traffic over time.
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.24. Source Payload Type
The source payload type reports payload formats (e.g., media
encoding) as sent by the data source, e.g., ITU G.711, ITU G.729B,
H.263, MPEG-2, ASCII, etc. This memo follows the definition of
Payload Type (PT) in [RFC3551]. For example, to indicate that the
source payload type used for a session is PCMA (pulse-code modulation
with A-law scaling), the value of the source payload field for the
respective session will be 8.
The source payload type value is expected to remain constant for the
duration of a session, with the exception of events like dynamic
codec changes. RDSs SHOULD avoid sending these parameters within
RAQMON reports more often than necessary (e.g., at dynamic codec
changes) to ensure an efficient usage of network resources.
If dynamic types (values 96 to 127, according to [RFC3551]) are being
used to identify the source payload type, a RAQMON extension
parameter MAY be defined to indicate the MIME subtypes. In the case
where the RDS does send reports noting dynamic codec changes, there
may be instances where this extension parameter is used only before
or after the codec change, as the source payload may shift between
the dynamic and static types.
5.25. Receiver Payload Type
The receiver payload type reports payload formats (e.g., media
encodings) as sent by the other communicating party back to the
source, e.g., ITU G.711, ITU G.729B, H.263, MPEG-2, ASCII, etc. This
document follows the definition of payload type (PT) in [RFC3551].
For example, to indicate that the destination payload type used for a
session is PCMA, the destination payload type field for the
respective session will be 8.
The destination payload type value is expected to remain constant for
the duration of a session, with the exception of events like dynamic
codec changes. RDSs SHOULD avoid sending these parameters within
RAQMON reports more often than necessary (e.g., at dynamic codec
changes) to ensure an efficient usage of network resources.
If dynamic types (values 96 to 127, according to [RFC3551]) are being
used to identify the destination payload type, a RAQMON extension
parameter MAY be defined to indicate the MIME subtypes. In the case
where the RDS does send reports noting dynamic codec changes, there
may be instances where this extension parameter is used only before
or after the codec change, as the destination payload may shift
between the dynamic and static types.
5.26. Source Layer 2 Priority
Many devices use Layer 2 technologies to prioritize certain types of
traffic in the Local Area Network environment. For example, the 1998
Edition of IEEE 802.1D [IEEE802.1D], "Media Access Control Bridges",
contains expedited traffic capabilities to support transmission of
time-critical information. Many devices use that standard to mark
Ethernet frames according to IEEE P802.1p standard. Details on these
can be found in [IEEE802.1D], which incorporates P802.1p. The Source
Layer 2 Priority RAQMON field indicates what Layer 2 values were used
by the host running the RDS to prioritize these packets in the Local
Area Network environment.
The Source Layer 2 Priority value is expected to remain constant for
the duration of a session. Hosts running the RDSs SHOULD avoid
sending these parameters within RAQMON reports too often in order to
ensure an efficient usage of network resources.
5.27. Source TOS/DSCP Value
Various Layer 3 technologies are in place to prioritize traffic in
the Internet. For example, the traditional IP Precedence [RFC791]
and Type of Service (TOS) [RFC1812], or more recent technologies like
Differentiated Services [RFC2474] [RFC2475], use the TOS octet in
IPv4, whereas the traffic class octet is used to prioritize traffic
in IPv6. Source Layer TOS/DCP RAQMON field reports the appropriate
Layer 3 values used by the Data Source to prioritize these packets.
The Source TOS/DSCP value is expected to remain constant for the
duration of a session. Hosts running the RDSs SHOULD avoid sending
these parameters within RAQMON reports too often in order to ensure
an efficient usage of network resources.
5.28. Destination Layer 2 Priority
The Destination Layer 2 Priority reports the Layer 2 value used by
the communication receiver to prioritize packets while sending
traffic to the data source in the Local Area Networks environment.
Like Source Layer 2 Priority, Destination Layer 2 Priority could
indicate whether the destination has used Layer 2 technologies like
IEEE P802.1p for priority queuing.
The Destination Layer 2 Priority value is expected to remain constant
for the duration of a session. Hosts running the RDSs SHOULD avoid
sending these parameters within RAQMON reports too often in order to
ensure an efficient usage of network resources.
5.29. Destination TOS/DSCP Value
The Destination TOS/DSCP RAQMON field reports the values used by the
Data Receiver to prioritize these packets received by the source.
Similar to Source Layer 3 Priority, Destination Layer 3 Priority
indicates whether the destination has used any Layer 3 technologies
like IP Precedence [RFC791] and Type of Service (TOS) [RFC1812], or
more recent technologies like Differentiated Service [RFC2474]
[RFC2475].
The Destination TOS/DSCP value is expected to remain constant for the
duration of a session. Hosts running the RDSs SHOULD avoid sending
these parameters within RAQMON reports too often in order to ensure
an efficient usage of network resources.
5.30. CPU Utilization in Fraction
This parameter captures the CPU usage of the hosts running the RDSs
that may have very critical implications for QoS of an end-device.
It is computed as an average since the last reporting interval, and
corresponds to the percentage of that time that the CPU was busy.
In the case of multiple CPU hosts, the maximum utilization among the
different CPUs MUST be reported.
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.31. Memory Utilization in Fraction
This parameter captures the memory usage of the hosts running the
RDSs that may have very critical implications for QoS of an end-
device. It is computed as an average since the last reporting
interval and corresponds to the average percentage of the total
memory space critical for the applications in use during that time
interval (e.g., primary CPU RAM, buffers).
In the case of multiple CPU hosts, the maximum memory utilization
among the different CPUs MUST be reported.
This parameter SHOULD be sent in each RAQMON PDU, if the RDS has the
capability of determining its value and if the parameter is relevant
for the application.
5.32. Application Name/Version
The Application Name/Version parameter gives the name and,
optionally, the version of the application associated with that
session or sub-session, e.g., "XYZ VoIP Agent 1.2". This information
may be useful for scenarios where the end-device is running multiple
applications with various priorities and could be very handy for
debugging purposes.
If the application is using RTP [RFC3550], the Application Name
SHOULD begin with the string 'RTP'.
This parameter MUST be sent in the first RAQMON PDU.
6. Report Aggregation and Statistical Data processing
Within the RAQMON Framework, RRCs are expected to have significantly
greater computational resources than RDSs. Consequently, various
aggregation functions are performed by the RRCs, while RDSs are not
burdened by statistical data processing such as computation of
minima, maxima, averages, standard deviations, etc.
The RAQMON MIB provides minimal aggregation of the RAQMON parameters
defined above. The RAQMON MIB is not designed to provide extensive
aggregation like the Application Performance Measurement (APM) MIB
[RFC3729] or the Transport Performance Metrics (TPM) MIB [RFC4150].
One should use APM and TPM MIBs to aggregate parameters based on
protocols (e.g., performance of HTTP, RTP) or applications (e.g.,
performance of VoIP, Video Applications).
In the RAQMON MIB, aggregation can be performed only on specific
RAQMON metric parameters. Aggregation always results in statistical
Mean/Min/Max values, according to these definitions:
Mean: Mean is defined as the statistical average of a metric over
the duration of a communication session. For example, if an
RDS reported End-to-End delay metric N times within a
communication session, then the Mean End-to-End Delay can be
computed by summing of these N reported values, and then
dividing by N.
Min: Min is defined as the statistical minimum of a metric over
the duration of a communication session. For example, if
the end-to-end delay metric of an end-device within a
communication session is reported N times by the RDS, then
the Min end-to-end delay is the smallest of the N end-to-end
delay metric values reported.
Max: Max is defined as the statistical maximum of a metric over
the duration of a communication session. For example, if
the end-to-end delay metric of an end-device within a
communication session is reported N times by the RDS, then
the Max End-to-End Delay is the largest of the N End-to-End
Delay metric values reported.
7. Keeping Historical Data and Storage
It is evident from the document that the RAQMON MIB data need to be
managed to optimize storage space. The large volume of data gathered
in a communication session could be optimized for storage space by
performing and storing only aggregated RAQMON metrics for history if
required.
Examples of how such storage space optimization can be performed
include:
1. Make data available through the MIB only at the end of a
communication session, i.e., upon receipt of a NULL PDU. The
aggregated data could be made available using the RAQMON MIB as
Mean, Max, or Min entries and saved for historical purposes.
2. Use a time-based algorithm that aggregates data over a specific
period of time within a communication session, thus requiring
fewer entries, to reduce storage space requirements. For
example, if an RDS sends data out every 10 seconds and the RRC
updates the RAQMON MIB once every minute, for every 6 data
points there would be one MIB entry.
3. Periodically delete historical data in accordance with an
administrative policy. An example of such a policy would be to
delete historical data older than 60 days. The implementation
of such policies is left to the application developer's
discretion, and their use is an operational concern.
8. Security Considerations
Security considerations associated with the RAQMON Framework are
discussed below, and in greater detail in other RAQMON memos as is
appropriate.
8.1. The RAQMON Threat Model
The vulnerabilities associated with the RAQMON Framework are a
combination of those associated with the underlying layers up to the
transport layer, and of possible exploits of RAQMON payload.
Possible exploits of RAQMON payloads fall within these classes:
1. Unauthorized examination of sensitive information in the
payload in transit.
2. Unauthorized modification of payload contents in transit,
leading to:
a. Mis-identification of information from one RAQMON reporting
session as belonging to another destined to the same RRC;
b. Mismapping of RAQMON sessions;
c. Various forms of session-level denial-of-service (DoS)
attacks;
d. DoS through modification of RAQMON parameter values and
statistics;
e. Invalid timestamps, leading to false interpretation of the
monitored data, affecting call records information, and
making difficult to place monitoring events in their
appropriate temporal context.
3. Malformed payloads, permitting the exploitation of potential
implementation weaknesses to compromise an RRC.
4. Unauthorized disclosure of sensitive data carried by
application PDUs, leading to a breach of confidentiality.
Consequently, threats based on unauthorized disclosure or
modification of payloads or headers will have to be assumed.
8.2. The RAQMON Security Requirements and Assumptions
In order to preserve integrity of the RAQMON PDU against these
threats, the RAQMON model must provide for cryptographically strong
security services.
Consequently, the RAQMON framework must be able to provide for the
following protections:
1. Authentication - the RRC should be able to verify that a RAQMON
PDU was in fact originated by the RDS that claims to have sent
it.
2. Privacy - Since RAQMON information includes identification of
the parties participating in a communication session, the
RAQMON framework should be able to provide for protection from
eavesdropping, to prevent an unauthorized third party from
gathering potentially sensitive information. This can be
achieved by using various payload encryption technologies, such
as Data Encryption Standard (DES), 3-DES, Advanced Encryption
Standard (AES), etc.
3. Protection from DoS attacks directed at the RRC - RDSs send
RAQMON reports as a side effect of an external event (for
example, a phone call is being received). An attacker can try
to overwhelm the RRC (or the network) by initiating a large
number of events (i.e., calls) for the purpose of swamping the
RRC with too many RAQMON PDUs.
To prevent DoS attacks against RRC, the RDS will send the first
report for a session only after the session has been in
progress for the five-second reporting interval. Sessions
shorter than that should be stored in the RDS and will be
reported only after that interval has expired.
8.3. RAQMON Security Model
The RAQMON architecture permits the use of multiple transport
protocols. Most of these support a secure mode of operation. There
are advantages to relying on the security provided at the transport
protocol layer.
1. Transport-protocol-level security can generally protect the
payload with end-to-end authentication, confidentiality,
message integrity, and replay protection services.
2. A good cryptographic security protocol always has an associated
key management protocol. Use of transport protocol security
relies on its key management and does not require development
of another mechanism.
3. When transport protocol security is already enabled between the
RDS and RRC, additional encryption and message authentication
at the application level is avoided.
However, there are also shortcomings to be noted in relying on
transport protocol security.
1. When session-level isolation of the different RAQMON sessions
of an RDS-RRC pair is required, it will be necessary to open
separate transport protocol instances. Such cases, however,
may be rare.
2. Since security services are not provided by the RAQMON
framework, the absence of transport or lower protocol security
implies the absence of RAQMON security.
9. Acknowledgements
The authors would like to thank Andy Bierman, Alan Clark, Mahalingam
Mani, Colin Perkins, Steve Waldbusser, Magnus Westerlund, and Itai
Zilbershtein for the precious advices and real contributions brought
to this document. The authors would also like to extend special
thanks to Randy Presuhn, who reviewed this document for spelling and
formatting purposes, and who provided a deep review of the technical
content. We also would like to thank Bert Wijnen for the permanent
coaching during the evolution of this document and the detailed
review of its final versions.
10. Normative References
[RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
[RFC1812] Baker, F., "Requirements for IP Version 4 Routers", RFC
1812, June 1995.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474, December
1998.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Service", RFC 2475, December 1998.
[RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Delay Metric for IPPM", RFC 2679, September 1999.
[RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Packet Loss Metric for IPPM", RFC 2680, September 1999.
[RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-
trip Delay Metric for IPPM", RFC 2681, September 1999.
[RFC2819] Waldbusser, S., "Remote Network Monitoring Management
Information Base", STD 59, RFC 2819, May 2000.
[RFC2959] Baugher, M., Strahm, B., and I. Suconick, "Real-Time
Transport Protocol Management Information Base", RFC
2959, October 2000.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay
Variation Metric for IP Performance Metrics (IPPM)", RFC
3393, November 2002.
[RFC3416] Presuhn, R., Ed., "Version 2 of the Protocol Operations
for the Simple Network Management Protocol (SNMP)", STD
62, RFC 3416, 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.
[RFC3551] Schulzrinne, H. and S. Casner, "RTP Profile for Audio
and Video Conferences with Minimal Control", STD 65, RFC
3551, July 2003.
11. Informative References
[RFC1034] Mockapetris, P., "Domain names - concepts and
facilities", STD 13, RFC 1034, November 1987.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC1123] Braden, R., "Requirements for Internet Hosts -
Application and Support", STD 3, RFC 1123, October 1989.
[RFC1305] Mills, D., "Network Time Protocol (Version 3)
Specification, Implementation and Analysis", RFC 1305,
March 1992.
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot,
G., and E. Lear, "Address Allocation for Private
Internets", BCP 5, RFC 1918, February 1996.
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, RFC
2914, September 2000.
[RFC3235] Senie, D., "Network Address Translator (NAT)-Friendly
Application Design Guidelines", RFC 3235, January 2002.
[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", RFC 3611, November
2003.
[RFC3729] Waldbusser, S., "Application Performance Measurement
MIB", RFC 3729, March 2004.
[RFC4150] Dietz, R. and R. Cole, "Transport Performance Metrics
MIB", RFC 4150, August 2005.
[RFC4711] Siddiqui, A., Romascanu, D., and E. Golovinsky, "Real-
time Application Quality-of-Service Monitoring (RAQMON)
MIB", RFC 4711, October 2006.
[RFC4712] Siddiqui, A., Romascanu, D., Golovinsky, E., Ramhman,
M., and Y. Kim, "Transport Mappings for Real-time
Application Quality-of-Service Monitoring (RAQMON)
Protocol Data Unit (PDU)", RFC 4712, October 2006.
[IEEE802.1D] Information technology - Telecommunications and
information exchange between systems - Local and
metropolitan area networks - Common Specification a -
Media access control (MAC) bridges:15802-3: 1998
(ISO/IEC). Revision. This is a revision of ISO/IEC
10038: 1993, 802.1j-1992 and 802.6k-1992. It
incorporates P802.11c, P802.1p and P802.12e [ANSI/IEEE
Std 802.1D, 1998 Edition]
Authors' Addresses
Anwar A. Siddiqui
Avaya Labs
307 Middletown Lincroft Road
Lincroft, New Jersey 07738
USA
Phone: +1 732 852-3200
EMail: anwars@avaya.com
Dan Romascanu
Avaya
Atidim Technology Park, Building #3
Tel Aviv, 61131
Israel
Phone: +972-3-645-8414
EMail: dromasca@avaya.com
Eugene Golovinsky
EMail: gene@alertlogic.net
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