| Rfc | 5920 |
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| Title | Security Framework for MPLS and GMPLS Networks |
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| Author | L. Fang, Ed. |
|---|
| Date | July
2010 |
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| Format: | TXT, HTML |
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| Status: | INFORMATIONAL |
|---|
|
Internet Engineering Task Force (IETF) L. Fang, Ed.
Request for Comments: 5920 Cisco Systems, Inc.
Category: Informational July 2010
ISSN: 2070-1721
Security Framework for MPLS and GMPLS Networks
Abstract
This document provides a security framework for Multiprotocol Label
Switching (MPLS) and Generalized Multiprotocol Label Switching
(GMPLS) Networks. This document addresses the security aspects that
are relevant in the context of MPLS and GMPLS. It describes the
security threats, the related defensive techniques, and the
mechanisms for detection and reporting. This document emphasizes
RSVP-TE and LDP security considerations, as well as inter-AS and
inter-provider security considerations for building and maintaining
MPLS and GMPLS networks across different domains or different
Service Providers.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5920.
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than English.
1. Introduction
Security is an important aspect of all networks, MPLS and GMPLS
networks being no exception.
MPLS and GMPLS are described in [RFC3031] and [RFC3945]. Various
security considerations have been addressed in each of the many RFCs
on MPLS and GMPLS technologies, but no single document covers general
security considerations. The motivation for creating this document
is to provide a comprehensive and consistent security framework for
MPLS and GMPLS networks. Each individual document may point to this
document for general security considerations in addition to providing
security considerations specific to the particular technologies the
document is describing.
In this document, we first describe the security threats relevant in
the context of MPLS and GMPLS and the defensive techniques to combat
those threats. We consider security issues resulting both from
malicious or incorrect behavior of users and other parties and from
negligent or incorrect behavior of providers. An important part of
security defense is the detection and reporting of a security attack,
which is also addressed in this document.
We then discuss possible service provider security requirements in an
MPLS or GMPLS environment. Users have expectations for the security
characteristics of MPLS or GMPLS networks. These include security
requirements for equipment supporting MPLS and GMPLS and operational
security requirements for providers. Service providers must protect
their network infrastructure and make it secure to the level required
to provide services over their MPLS or GMPLS networks.
Inter-AS and inter-provider security are discussed with special
emphasis, because the security risk factors are higher with inter-
provider connections. Note that inter-carrier MPLS security is also
considered in [MFA-MPLS-ICI].
Depending on different MPLS or GMPLS techniques used, the degree of
risk and the mitigation methodologies vary. This document discusses
the security aspects and requirements for certain basic MPLS and
GMPLS techniques and interconnection models. This document does not
attempt to cover all current and future MPLS and GMPLS technologies,
as it is not within the scope of this document to analyze the
security properties of specific technologies.
It is important to clarify that, in this document, we limit ourselves
to describing the providers' security requirements that pertain to
MPLS and GMPLS networks, not including the connected user sites.
Readers may refer to the "Security Best Practices Efforts and
Documents" [OPSEC-EFFORTS] and "Security Mechanisms for the Internet"
[RFC3631] for general network operation security considerations. It
is not our intention, however, to formulate precise "requirements"
for each specific technology in terms of defining the mechanisms and
techniques that must be implemented to satisfy such security
requirements.
2. Terminology
2.1. Acronyms and Abbreviations
AS Autonomous System
ASBR Autonomous System Border Router
ATM Asynchronous Transfer Mode
BGP Border Gateway Protocol
BFD Bidirectional Forwarding Detection
CE Customer-Edge device
CoS Class of Service
CPU Central Processing Unit
DNS Domain Name System
DoS Denial of Service
ESP Encapsulating Security Payload
FEC Forwarding Equivalence Class
GMPLS Generalized Multi-Protocol Label Switching
GCM Galois Counter Mode
GRE Generic Routing Encapsulation
ICI InterCarrier Interconnect
ICMP Internet Control Message Protocol
ICMPv6 ICMP in IP Version 6
IGP Interior Gateway Protocol
IKE Internet Key Exchange
IP Internet Protocol
IPsec IP Security
IPVPN IP-based VPN
LDP Label Distribution Protocol
L2TP Layer 2 Tunneling Protocol
LMP Link Management Protocol
LSP Label Switched Path
LSR Label Switching Router
MD5 Message Digest Algorithm
MPLS Multiprotocol Label Switching
MP-BGP Multiprotocol BGP
NTP Network Time Protocol
OAM Operations, Administration, and Maintenance
PCE Path Computation Element
PE Provider-Edge device
PPVPN Provider-Provisioned Virtual Private Network
PSN Packet-Switched Network
PW Pseudowire
QoS Quality of Service
RR Route Reflector
RSVP Resource Reservation Protocol
RSVP-TE Resource Reservation Protocol with Traffic Engineering
Extensions
SLA Service Level Agreement
SNMP Simple Network Management Protocol
SP Service Provider
SSH Secure Shell
SSL Secure Sockets Layer
SYN Synchronize packet in TCP
TCP Transmission Control Protocol
TDM Time Division Multiplexing
TE Traffic Engineering
TLS Transport Layer Security
ToS Type of Service
TTL Time-To-Live
UDP User Datagram Protocol
VC Virtual Circuit
VPN Virtual Private Network
WG Working Group of IETF
WSS Web Services Security
2.2. MPLS and GMPLS Terminology
This document uses MPLS- and GMPLS-specific terminology. Definitions
and details about MPLS and GMPLS terminology can be found in
[RFC3031] and [RFC3945]. The most important definitions are repeated
in this section; for other definitions, the reader is referred to
[RFC3031] and [RFC3945].
Core network: An MPLS/GMPLS core network is defined as the central
network infrastructure that consists of P and PE routers. An
MPLS/GMPLS core network may consist of one or more networks belonging
to a single SP.
Customer Edge (CE) device: A Customer Edge device is a router or a
switch in the customer's network interfacing with the Service
Provider's network.
Forwarding Equivalence Class (FEC): A group of IP packets that are
forwarded in the same manner (e.g., over the same path, with the same
forwarding treatment).
Label: A short, fixed length, physically contiguous identifier,
usually of local significance.
Label merging: the replacement of multiple incoming labels for a
particular FEC with a single outgoing label.
Label Switched Hop: A hop between two MPLS nodes, on which forwarding
is done using labels.
Label Switched Path (LSP): The path through one or more LSRs at one
level of the hierarchy followed by packets in a particular FEC.
Label Switching Routers (LSRs): An MPLS/GMPLS node assumed to have a
forwarding plane that is capable of (a) recognizing either packet or
cell boundaries, and (b) being able to process either packet headers
or cell headers.
Loop Detection: A method of dealing with loops in which loops are
allowed to be set up, and data may be transmitted over the loop, but
the loop is later detected.
Loop Prevention: A method of dealing with loops in which data is
never transmitted over a loop.
Label Stack: An ordered set of labels.
Merge Point: A node at which label merging is done.
MPLS Domain: A contiguous set of nodes that perform MPLS routing and
forwarding and are also in one Routing or Administrative Domain.
MPLS Edge Node: An MPLS node that connects an MPLS domain with a node
outside of the domain, either because it does not run MPLS, or
because it is in a different domain. Note that if an LSR has a
neighboring host not running MPLS, then that LSR is an MPLS edge
node.
MPLS Egress Node: An MPLS edge node in its role in handling traffic
as it leaves an MPLS domain.
MPLS Ingress Node: A MPLS edge node in its role in handling traffic
as it enters a MPLS domain.
MPLS Label: A label carried in a packet header, which represents the
packet's FEC.
MPLS Node: A node running MPLS. An MPLS node is aware of MPLS
control protocols, runs one or more routing protocols, and is capable
of forwarding packets based on labels. An MPLS node may optionally
be also capable of forwarding native IP packets.
Multiprotocol Label Switching (MPLS): MPLS is an architecture for
efficient data packet switching and routing. MPLS assigns data
packets with labels. Instead of performing the longest match for
each packet's destination as in conventional IP forwarding, MPLS
makes the packet-forwarding decisions solely on the contents of the
label without examining the packet itself. This allows the creation
of end-to-end circuits across any type of transport medium, using any
protocols.
P: Provider Router. A Provider Router is a router in the Service
Provider's core network that does not have interfaces directly
towards the customer. A P router is used to interconnect the PE
routers and/or other P routers within the core network.
PE: Provider Edge device. A Provider Edge device is the equipment in
the Service Provider's network that interfaces with the equipment in
the customer's network.
PPVPN: Provider-Provisioned Virtual Private Network, including Layer
2 VPNs and Layer 3 VPNs.
VPN: Virtual Private Network, which restricts communication between a
set of sites, making use of an IP backbone shared by traffic not
going to or not coming from those sites [RFC4110].
3. Security Reference Models
This section defines a reference model for security in MPLS/GMPLS
networks.
This document defines each MPLS/GMPLS core in a single domain to be a
trusted zone. A primary concern is about security aspects that
relate to breaches of security from the "outside" of a trusted zone
to the "inside" of this zone. Figure 1 depicts the concept of
trusted zones within the MPLS/GMPLS framework.
/-------------\
+------------+ / \ +------------+
| MPLS/GMPLS +---/ \--------+ MPLS/GMPLS |
| user | MPLS/GMPLS Core | user |
| site +---\ /XXX-----+ site |
+------------+ \ / XXX +------------+
\-------------/ | |
| |
| +------\
+--------/ "Internet"
|<- Trusted zone ->|
MPLS/GMPLS Core with user connections and Internet connection
Figure 1: The MPLS/GMPLS Trusted Zone Model
The trusted zone is the MPLS/GMPLS core in a single AS within a
single Service Provider.
A trusted zone contains elements and users with similar security
properties, such as exposure and risk level. In the MPLS context, an
organization is typically considered as one trusted zone.
The boundaries of a trust domain should be carefully defined when
analyzing the security properties of each individual network, e.g.,
the boundaries can be at the link termination, remote peers, areas,
or quite commonly, ASes.
In principle, the trusted zones should be separate; however,
typically MPLS core networks also offer Internet access, in which
case a transit point (marked with "XXX" in Figure 1) is defined. In
the case of MPLS/GMPLS inter-provider connections or InterCarrier
Interconnect (ICI), the trusted zone of each provider ends at the
respective ASBRs (ASBR1 and ASBR2 for Provider A and ASBR3 and ASBR4
for Provider B in Figure 2).
A key requirement of MPLS and GMPLS networks is that the security of
the trusted zone not be compromised by interconnecting the MPLS/GMPLS
core infrastructure with another provider's core (MPLS/GMPLS or non-
MPLS/GMPLS), the Internet, or end users.
In addition, neighbors may be trusted or untrusted. Neighbors may be
authorized or unauthorized. An authorized neighbor is the neighbor
one establishes a peering relationship with. Even though a neighbor
may be authorized for communication, it may not be trusted. For
example, when connecting with another provider's ASBRs to set up
inter-AS LSPs, the other provider is considered an untrusted but
authorized neighbor.
+---------------+ +----------------+
| | | |
| MPLS/GMPLS ASBR1----ASBR3 MPLS/GMPLS |
CE1--PE1 Network | | Network PE2--CE2
| Provider A ASBR2----ASBR4 Provider B |
| | | |
+---------------+ +----------------+
InterCarrier
Interconnect (ICI)
For Provider A:
Trusted Zone: Provider A MPLS/GMPLS network
Authorized but untrusted neighbor: provider B
Unauthorized neighbors: CE1, CE2
Figure 2: MPLS/GMPLS Trusted Zone and Authorized Neighbor
All aspects of network security independent of whether a network is
an MPLS/GMPLS network, are out of scope. For example, attacks from
the Internet to a user's web-server connected through the MPLS/GMPLS
network are not considered here, unless the way the MPLS/GMPLS
network is provisioned could make a difference to the security of
this user's server.
4. Security Threats
This section discusses the various network security threats that may
endanger MPLS/GMPLS networks. RFC 4778 [RFC4778] provided the best
current operational security practices in Internet Service Provider
environments.
A successful attack on a particular MPLS/GMPLS network or on an SP's
MPLS/GMPLS infrastructure may cause one or more of the following ill
effects:
- Observation, modification, or deletion of a provider's or user's
data.
- Replay of a provider's or user's data.
- Injection of inauthentic data into a provider's or user's traffic
stream.
- Traffic pattern analysis on a provider's or user's traffic.
- Disruption of a provider's or user's connectivity.
- Degradation of a provider's service quality.
- Probing a provider's network to determine its configuration,
capacity, or usage.
It is useful to consider that threats, whether malicious or
accidental, may come from different categories of sources. For
example, they may come from:
- Other users whose services are provided by the same MPLS/GMPLS
core.
- The MPLS/GMPLS SP or persons working for it.
- Other persons who obtain physical access to an MPLS/GMPLS SP's
site.
- Other persons who use social engineering methods to influence the
behavior of an SP's personnel.
- Users of the MPLS/GMPLS network itself, e.g., intra-VPN threats.
(Such threats are beyond the scope of this document.)
- Others, e.g., attackers from the Internet at large.
- Other SPs in the case of MPLS/GMPLS inter-provider connection.
The core of the other provider may or may not be using MPLS/GMPLS.
- Those who create, deliver, install, and maintain software for
network equipment.
Given that security is generally a tradeoff between expense and risk,
it is also useful to consider the likelihood of different attacks
occurring. There is at least a perceived difference in the
likelihood of most types of attacks being successfully mounted in
different environments, such as:
- An MPLS/GMPLS core interconnecting with another provider's core.
- An MPLS/GMPLS configuration transiting the public Internet.
Most types of attacks become easier to mount and hence more likely as
the shared infrastructure via which service is provided expands from
a single SP to multiple cooperating SPs to the global Internet.
Attacks that may not be of sufficient likeliness to warrant concern
in a closely controlled environment often merit defensive measures in
broader, more open environments. In closed communities, it is often
practical to deal with misbehavior after the fact: an employee can be
disciplined, for example.
The following sections discuss specific types of exploits that
threaten MPLS/GMPLS networks.
4.1. Attacks on the Control Plane
This category encompasses attacks on the control structures operated
by the SP with MPLS/GMPLS cores.
It should be noted that while connectivity in the MPLS control plane
uses the same links and network resources as are used by the data
plane, the GMPLS control plane may be provided by separate resources
from those used in the data plane. That is, the GMPLS control plane
may be physically separate from the data plane.
The different cases of physically congruent and physically separate
control/data planes lead to slightly different possibilities of
attack, although most of the cases are the same. Note that, for
example, the data plane cannot be directly congested by an attack on
a physically separate control plane as it could be if the control and
data planes shared network resources. Note also that if the control
plane uses diverse resources from the data plane, no assumptions
should be made about the security of the control plane based on the
security of the data plane resources.
This section is focused the outsider attack. The insider attack is
discussed in Section 4.4.
4.1.1. LSP Creation by an Unauthorized Element
The unauthorized element can be a local CE or a router in another
domain. An unauthorized element can generate MPLS signaling
messages. At the least, this can result in extra control plane and
forwarding state, and if successful, network bandwidth could be
reserved unnecessarily. This may also result in theft of service or
even compromise the entire network.
4.1.2. LSP Message Interception
This threat might be accomplished by monitoring network traffic, for
example, after a physical intrusion. Without physical intrusion, it
could be accomplished with an unauthorized software modification.
Also, many technologies such as terrestrial microwave, satellite, or
free-space optical could be intercepted without physical intrusion.
If successful, it could provide information leading to label spoofing
attacks. It also raises confidentiality issues.
4.1.3. Attacks against RSVP-TE
RSVP-TE, described in [RFC3209], is the control protocol used to set
up GMPLS and traffic engineered MPLS tunnels.
There are two major types of denial-of-service (DoS) attacks against
an MPLS domain based on RSVP-TE. The attacker may set up numerous
unauthorized LSPs or may send a storm of RSVP messages. It has been
demonstrated that unprotected routers running RSVP can be effectively
disabled by both types of DoS attacks.
These attacks may even be combined, by using the unauthorized LSPs to
transport additional RSVP (or other) messages across routers where
they might otherwise be filtered out. RSVP attacks can be launched
against adjacent routers at the border with the attacker, or against
non-adjacent routers within the MPLS domain, if there is no effective
mechanism to filter them out.
4.1.4. Attacks against LDP
LDP, described in [RFC5036], is the control protocol used to set up
MPLS tunnels without TE.
There are two significant types of attack against LDP. An
unauthorized network element can establish an LDP session by sending
LDP Hello and LDP Init messages, leading to the potential setup of an
LSP, as well as accompanying LDP state table consumption. Even
without successfully establishing LSPs, an attacker can launch a DoS
attack in the form of a storm of LDP Hello messages or LDP TCP SYN
messages, leading to high CPU utilization or table space exhaustion
on the target router.
4.1.5. Denial-of-Service Attacks on the Network Infrastructure
DoS attacks could be accomplished through an MPLS signaling storm,
resulting in high CPU utilization and possibly leading to control-
plane resource starvation.
Control-plane DoS attacks can be mounted specifically against the
mechanisms the SP uses to provide various services, or against the
general infrastructure of the service provider, e.g., P routers or
shared aspects of PE routers. (An attack against the general
infrastructure is within the scope of this document only if the
attack can occur in relation with the MPLS/GMPLS infrastructure;
otherwise, it is not an MPLS/GMPLS-specific issue.)
The attacks described in the following sections may each have denial
of service as one of their effects. Other DoS attacks are also
possible.
4.1.6. Attacks on the SP's MPLS/GMPLS Equipment via Management
Interfaces
This includes unauthorized access to an SP's infrastructure
equipment, for example, to reconfigure the equipment or to extract
information (statistics, topology, etc.) pertaining to the network.
4.1.7. Cross-Connection of Traffic between Users
This refers to the event in which expected isolation between separate
users (who may be VPN users) is breached. This includes cases such
as:
- A site being connected into the "wrong" VPN.
- Traffic being replicated and sent to an unauthorized user.
- Two or more VPNs being improperly merged together.
- A point-to-point VPN connecting the wrong two points.
- Any packet or frame being improperly delivered outside the VPN to
which it belongs
Misconnection or cross-connection of VPNs may be caused by service
provider or equipment vendor error, or by the malicious action of an
attacker. The breach may be physical (e.g., PE-CE links
misconnected) or logical (e.g., improper device configuration).
Anecdotal evidence suggests that the cross-connection threat is one
of the largest security concerns of users (or would-be users).
4.1.8. Attacks against Routing Protocols
This encompasses attacks against underlying routing protocols that
are run by the SP and that directly support the MPLS/GMPLS core.
(Attacks against the use of routing protocols for the distribution of
backbone routes are beyond the scope of this document.) Specific
attacks against popular routing protocols have been widely studied
and are described in [RFC4593].
4.1.9. Other Attacks on Control Traffic
Besides routing and management protocols (covered separately in the
previous sections), a number of other control protocols may be
directly involved in delivering services by the MPLS/GMPLS core.
These include but may not be limited to:
- MPLS signaling (LDP, RSVP-TE) discussed above in subsections 4.1.4
and 4.1.3
- PCE signaling
- IPsec signaling (IKE and IKEv2)
- ICMP and ICMPv6
- L2TP
- BGP-based membership discovery
- Database-based membership discovery (e.g., RADIUS)
- Other protocols that may be important to the control
infrastructure, e.g., DNS, LMP, NTP, SNMP, and GRE.
Attacks might subvert or disrupt the activities of these protocols,
for example via impersonation or DoS.
Note that all of the data-plane attacks can also be carried out
against the packets of the control and management planes: insertion,
spoofing, replay, deletion, pattern analysis, and other attacks
mentioned above.
4.2. Attacks on the Data Plane
This category encompasses attacks on the provider's or end-user's
data. Note that from the MPLS/GMPLS network end user's point of
view, some of this might be control-plane traffic, e.g., routing
protocols running from user site A to user site B via IP or non-IP
connections, which may be some type of VPN.
4.2.1. Unauthorized Observation of Data Traffic
This refers to "sniffing" provider or end user packets and examining
their contents. This can result in exposure of confidential
information. It can also be a first step in other attacks (described
below) in which the recorded data is modified and re-inserted, or
simply replayed later.
4.2.2. Modification of Data Traffic
This refers to modifying the contents of packets as they traverse the
MPLS/GMPLS core.
4.2.3. Insertion of Inauthentic Data Traffic: Spoofing and Replay
Spoofing refers to sending a user packets or inserting packets into a
data stream that do not belong, with the objective of having them
accepted by the recipient as legitimate. Also included in this
category is the insertion of copies of once-legitimate packets that
have been recorded and replayed.
4.2.4. Unauthorized Deletion of Data Traffic
This refers to causing packets to be discarded as they traverse the
MPLS/GMPLS networks. This is a specific type of denial-of-service
attack.
4.2.5. Unauthorized Traffic Pattern Analysis
This refers to "sniffing" provider or user packets and examining
aspects or meta-aspects of them that may be visible even when the
packets themselves are encrypted. An attacker might gain useful
information based on the amount and timing of traffic, packet sizes,
source and destination addresses, etc. For most users, this type of
attack is generally considered to be significantly less of a concern
than the other types discussed in this section.
4.2.6. Denial-of-Service Attacks
Denial-of-service (DoS) attacks are those in which an attacker
attempts to disrupt or prevent the use of a service by its legitimate
users. Taking network devices out of service, modifying their
configuration, or overwhelming them with requests for service are
several of the possible avenues for DoS attack.
Overwhelming the network with requests for service, otherwise known
as a "resource exhaustion" DoS attack, may target any resource in the
network, e.g., link bandwidth, packet forwarding capacity, session
capacity for various protocols, CPU power, table size, storage
overflows, and so on.
DoS attacks of the resource exhaustion type can be mounted against
the data plane of a particular provider or end user by attempting to
insert (spoofing) an overwhelming quantity of inauthentic data into
the provider or end-user's network from outside of the trusted zone.
Potential results might be to exhaust the bandwidth available to that
provider or end user, or to overwhelm the cryptographic
authentication mechanisms of the provider or end user.
Data-plane resource exhaustion attacks can also be mounted by
overwhelming the service provider's general (MPLS/GMPLS-independent)
infrastructure with traffic. These attacks on the general
infrastructure are not usually an MPLS/GMPLS-specific issue, unless
the attack is mounted by another MPLS/GMPLS network user from a
privileged position. (For example, an MPLS/GMPLS network user might
be able to monopolize network data-plane resources and thus disrupt
other users.)
Many DoS attacks use amplification, whereby the attacker co-opts
otherwise innocent parties to increase the effect of the attack. The
attacker may, for example, send packets to a broadcast or multicast
address with the spoofed source address of the victim, and all of the
recipients may then respond to the victim.
4.2.7. Misconnection
Misconnection may arise through deliberate attack, or through
misconfiguration or misconnection of the network resources. The
result is likely to be delivery of data to the wrong destination or
black-holing of the data.
In GMPLS with physically diverse control and data planes, it may be
possible for data-plane misconnection to go undetected by the control
plane.
In optical networks under GMPLS control, misconnection may give rise
to physical safety risks as unprotected lasers may be activated
without warning.
4.3. Attacks on Operation and Management Plane
Attacks on the Operation and Management plane have been discussed
extensively as general network security issues over the last 20
years. RFC 4778 [RFC4778] may serve as the best current operational
security practices in Internet Service Provider environments. RFC
4377 [RFC4377] provided Operations and Management Requirements for
MPLS networks. See also the Security Considerations of RFC 4377 and
Section 7 of RFC 4378 [RFC4378].
Operation and Management across the MPLS-ICI could also be the source
of security threats on the provider infrastructure as well as the
service offered over the MPLS-ICI. A large volume of Operation and
Management messages could overwhelm the processing capabilities of an
ASBR if the ASBR is not properly protected. Maliciously generated
Operation and Management messages could also be used to bring down an
otherwise healthy service (e.g., MPLS Pseudowire), and therefore
affect service security. LSP ping does not support authentication
today, and that support should be a subject for future
considerations. Bidirectional Forwarding Detection (BFD), however,
does have support for carrying an authentication object. It also
supports Time-To-Live (TTL) processing as an anti-replay measure.
Implementations conformant with this MPLS-ICI should support BFD
authentication and must support the procedures for TTL processing.
Regarding GMPLS Operation and Management considerations in optical
interworking, there is a good discussion on security for management
interfaces to Network Elements [OIF-Sec-Mag].
Network elements typically have one or more (in some cases many)
Operation and Management interfaces used for network management,
billing and accounting, configuration, maintenance, and other
administrative activities.
Remote access to a network element through these Operation and
Management interfaces is frequently a requirement. Securing the
control protocols while leaving these Operation and Management
interfaces unprotected opens up a huge security vulnerability.
Network elements are an attractive target for intruders who want to
disrupt or gain free access to telecommunications facilities. Much
has been written about this subject since the 1980s. In the 1990s,
telecommunications facilities were identified in the U.S. and other
countries as part of the "critical infrastructure", and increased
emphasis was placed on thwarting such attacks from a wider range of
potentially well-funded and determined adversaries.
At one time, careful access controls and password management were a
sufficient defense, but are no longer. Networks using the TCP/IP
protocol suite are vulnerable to forged source addresses, recording
and later replay, packet sniffers picking up passwords, re-routing of
traffic to facilitate eavesdropping or tampering, active hijacking
attacks of TCP connections, and a variety of denial-of-service
attacks. The ease of forging TCP/IP packets is the main reason
network management protocols lacking strong security have not been
used to configure network elements (e.g., with the SNMP SET command).
Readily available hacking tools exist that let an eavesdropper on a
LAN take over one end of any TCP connection, so that the legitimate
party is cut off. In addition, enterprises and Service Providers in
some jurisdictions need to safeguard data about their users and
network configurations from prying. An attacker could eavesdrop and
observe traffic to analyze usage patterns and map a network
configuration; an attacker could also gain access to systems and
manipulate configuration data or send malicious commands.
Therefore, in addition to authenticating the human user, more
sophisticated protocol security is needed for Operation and
Management interfaces, especially when they are configured over
TCP/IP stacks. Finally, relying on a perimeter defense, such as
firewalls, is insufficient protection against "insider attacks" or
against penetrations that compromise a system inside the firewall as
a launching pad to attack network elements. The insider attack is
discussed in the following session.
4.4. Insider Attacks Considerations
The chain of trust model means that MPLS and GMPLS networks are
particularly vulnerable to insider attacks. These can be launched by
any malign person with access to any LSR in the trust domain.
Insider attacks could also be launched by compromised software within
the trust domain. Such attacks could, for example, advertise non-
existent resources, modify advertisements from other routers, request
unwanted LSPs that use network resources, or deny or modify
legitimate LSP requests.
Protection against insider attacks is largely for future study in
MPLS and GMPLS networks. Some protection can be obtained by
providing strict security for software upgrades and tight OAM access
control procedures. Further protection can be achieved by strict
control of user (i.e., operator) access to LSRs. Software change
management and change tracking (e.g., CVS diffs from text-based
configuration files) helps in spotting irregularities and human
errors. In some cases, configuration change approval processes may
also be warranted. Software tools could be used to check
configurations for consistency and compliance. Software tools may
also be used to monitor and report network behavior and activity in
order to quickly spot any irregularities that may be the result of an
insider attack.
5. Defensive Techniques for MPLS/GMPLS Networks
The defensive techniques discussed in this document are intended to
describe methods by which some security threats can be addressed.
They are not intended as requirements for all MPLS/GMPLS
implementations. The MPLS/GMPLS provider should determine the
applicability of these techniques to the provider's specific service
offerings, and the end user may wish to assess the value of these
techniques to the user's service requirements. The operational
environment determines the security requirements. Therefore,
protocol designers need to provide a full set of security services,
which can be used where appropriate.
The techniques discussed here include encryption, authentication,
filtering, firewalls, access control, isolation, aggregation, and
others.
Often, security is achieved by careful protocol design, rather than
by adding a security method. For example, one method of mitigating
DoS attacks is to make sure that innocent parties cannot be used to
amplify the attack. Security works better when it is "designed in"
rather than "added on".
Nothing is ever 100% secure. Defense therefore involves protecting
against those attacks that are most likely to occur or that have the
most direct consequences if successful. For those attacks that are
protected against, absolute protection is seldom achievable; more
often it is sufficient just to make the cost of a successful attack
greater than what the adversary will be willing or able to expend.
Successfully defending against an attack does not necessarily mean
the attack must be prevented from happening or from reaching its
target. In many cases, the network can instead be designed to
withstand the attack. For example, the introduction of inauthentic
packets could be defended against by preventing their introduction in
the first place, or by making it possible to identify and eliminate
them before delivery to the MPLS/GMPLS user's system. The latter is
frequently a much easier task.
5.1. Authentication
To prevent security issues arising from some DoS attacks or from
malicious or accidental misconfiguration, it is critical that devices
in the MPLS/GMPLS should only accept connections or control messages
from valid sources. Authentication refers to methods to ensure that
message sources are properly identified by the MPLS/GMPLS devices
with which they communicate. This section focuses on identifying the
scenarios in which sender authentication is required and recommends
authentication mechanisms for these scenarios.
Cryptographic techniques (authentication, integrity, and encryption)
do not protect against some types of denial-of-service attacks,
specifically resource exhaustion attacks based on CPU or bandwidth
exhaustion. In fact, the software-based cryptographic processing
required to decrypt or check authentication may in some cases
increase the effect of these resource exhaustion attacks. With a
hardware cryptographic accelerator, attack packets can be dropped at
line speed without a cost to software cycles. Cryptographic
techniques may, however, be useful against resource exhaustion
attacks based on the exhaustion of state information (e.g., TCP SYN
attacks).
The MPLS data plane, as presently defined, is not amenable to source
authentication, as there are no source identifiers in the MPLS packet
to authenticate. The MPLS label is only locally meaningful. It may
be assigned by a downstream node or upstream node for multicast
support.
When the MPLS payload carries identifiers that may be authenticated
(e.g., IP packets), authentication may be carried out at the client
level, but this does not help the MPLS SP, as these client
identifiers belong to an external, untrusted network.
5.1.1. Management System Authentication
Management system authentication includes the authentication of a PE
to a centrally managed network management or directory server when
directory-based "auto-discovery" is used. It also includes
authentication of a CE to the configuration server, when a
configuration server system is used.
Authentication should be bidirectional, including PE or CE to
configuration server authentication for the PE or CE to be certain it
is communicating with the right server.
5.1.2. Peer-to-Peer Authentication
Peer-to-peer authentication includes peer authentication for network
control protocols (e.g., LDP, BGP, etc.) and other peer
authentication (i.e., authentication of one IPsec security gateway by
another).
Authentication should be bidirectional, including PE or CE to
configuration server authentication for the PE or CE to be certain it
is communicating with the right server.
As indicated in Section 5.1.1, authentication should be
bidirectional.
5.1.3. Cryptographic Techniques for Authenticating Identity
Cryptographic techniques offer several mechanisms for authenticating
the identity of devices or individuals. These include the use of
shared secret keys, one-time keys generated by accessory devices or
software, user-ID and password pairs, and a range of public-private
key systems. Another approach is to use a hierarchical Certification
Authority system to provide digital certificates.
This section describes or provides references to the specific
cryptographic approaches for authenticating identity. These
approaches provide secure mechanisms for most of the authentication
scenarios required in securing an MPLS/GMPLS network.
5.2. Cryptographic Techniques
MPLS/GMPLS defenses against a wide variety of attacks can be enhanced
by the proper application of cryptographic techniques. These same
cryptographic techniques are applicable to general network
communications and can provide confidentiality (encryption) of
communication between devices, authenticate the identities of the
devices, and detect whether the data being communicated has been
changed during transit or replayed from previous messages.
Several aspects of authentication are addressed in some detail in a
separate "Authentication" section (Section 5.1).
Cryptographic methods add complexity to a service and thus, for a few
reasons, may not be the most practical solution in every case.
Cryptography adds an additional computational burden to devices,
which may reduce the number of user connections that can be handled
on a device or otherwise reduce the capacity of the device,
potentially driving up the provider's costs. Typically, configuring
encryption services on devices adds to the complexity of their
configuration and adds labor cost. Some key management system is
usually needed. Packet sizes are typically increased when the
packets are encrypted or have integrity checks or replay counters
added, increasing the network traffic load and adding to the
likelihood of packet fragmentation with its increased overhead.
(This packet length increase can often be mitigated to some extent by
data compression techniques, but at the expense of additional
computational burden.) Finally, some providers may employ enough
other defensive techniques, such as physical isolation or filtering
and firewall techniques, that they may not perceive additional
benefit from encryption techniques.
Users may wish to provide confidentiality end to end. Generally,
encrypting for confidentiality must be accompanied with cryptographic
integrity checks to prevent certain active attacks against the
encrypted communications. On today's processors, encryption and
integrity checks run extremely quickly, but key management may be
more demanding in terms of both computational and administrative
overhead.
The trust model among the MPLS/GMPLS user, the MPLS/GMPLS provider,
and other parts of the network is a major element in determining the
applicability of cryptographic protection for any specific MPLS/GMPLS
implementation. In particular, it determines where cryptographic
protection should be applied:
- If the data path between the user's site and the provider's PE is
not trusted, then it may be used on the PE-CE link.
- If some part of the backbone network is not trusted, particularly
in implementations where traffic may travel across the Internet or
multiple providers' networks, then the PE-PE traffic may be
cryptographically protected. One also should consider cases where
L1 technology may be vulnerable to eavesdropping.
- If the user does not trust any zone outside of its premises, it
may require end-to-end or CE-CE cryptographic protection. This
fits within the scope of this MPLS/GMPLS security framework when
the CE is provisioned by the MPLS/GMPLS provider.
- If the user requires remote access to its site from a system at a
location that is not a customer location (for example, access by a
traveler), there may be a requirement for cryptographically
protecting the traffic between that system and an access point or
a customer's site. If the MPLS/GMPLS provider supplies the access
point, then the customer must cooperate with the provider to
handle the access control services for the remote users. These
access control services are usually protected cryptographically,
as well.
Access control usually starts with authentication of the entity. If
cryptographic services are part of the scenario, then it is important
to bind the authentication to the key management. Otherwise, the
protocol is vulnerable to being hijacked between the authentication
and key management.
Although CE-CE cryptographic protection can provide integrity and
confidentiality against third parties, if the MPLS/GMPLS provider has
complete management control over the CE (encryption) devices, then it
may be possible for the provider to gain access to the user's traffic
or internal network. Encryption devices could potentially be
reconfigured to use null encryption, bypass cryptographic processing
altogether, reveal internal configuration, or provide some means of
sniffing or diverting unencrypted traffic. Thus an implementation
using CE-CE encryption needs to consider the trust relationship
between the MPLS/GMPLS user and provider. MPLS/GMPLS users and
providers may wish to negotiate a service level agreement (SLA) for
CE-CE encryption that provides an acceptable demarcation of
responsibilities for management of cryptographic protection on the CE
devices. The demarcation may also be affected by the capabilities of
the CE devices. For example, the CE might support some partitioning
of management, a configuration lock-down ability, or shared
capability to verify the configuration. In general, the MPLS/GMPLS
user needs to have a fairly high level of trust that the MPLS/GMPLS
provider will properly provision and manage the CE devices, if the
managed CE-CE model is used.
5.2.1. IPsec in MPLS/GMPLS
IPsec [RFC4301] [RFC4302] [RFC4835] [RFC4306] [RFC4309] [RFC2411]
[IPSECME-ROADMAP] is the security protocol of choice for protection
at the IP layer. IPsec provides robust security for IP traffic
between pairs of devices. Non-IP traffic, such as IS-IS routing,
must be converted to IP (e.g., by encapsulation) in order to use
IPsec. When the MPLS is encapsulating IP traffic, then IPsec covers
the encryption of the IP client layer; for non-IP client traffic, see
Section 5.2.4 (MPLS PWs).
In the MPLS/GMPLS model, IPsec can be employed to protect IP traffic
between PEs, between a PE and a CE, or from CE to CE. CE-to-CE IPsec
may be employed in either a provider-provisioned or a user-
provisioned model. Likewise, IPsec protection of data performed
within the user's site is outside the scope of this document, because
it is simply handled as user data by the MPLS/GMPLS core. However,
if the SP performs compression, pre-encryption will have a major
effect on that operation.
IPsec does not itself specify cryptographic algorithms. It can use a
variety of integrity or confidentiality algorithms (or even combined
integrity and confidentiality algorithms) with various key lengths,
such as AES encryption or AES message integrity checks. There are
trade-offs between key length, computational burden, and the level of
security of the encryption. A full discussion of these trade-offs is
beyond the scope of this document. In practice, any currently
recommended IPsec protection offers enough security to reduce the
likelihood of its being directly targeted by an attacker
substantially; other weaker links in the chain of security are likely
to be attacked first. MPLS/GMPLS users may wish to use a Service
Level Agreement (SLA) specifying the SP's responsibility for ensuring
data integrity and confidentiality, rather than analyzing the
specific encryption techniques used in the MPLS/GMPLS service.
Encryption algorithms generally come with two parameters: mode such
as Cipher Block Chaining and key length such as AES-192. (This
should not be confused with two other senses in which the word "mode"
is used: IPsec itself can be used in Tunnel Mode or Transport Mode,
and IKE [version 1] uses Main Mode, Aggressive Mode, or Quick Mode).
It should be stressed that IPsec encryption without an integrity
check is a state of sin.
For many of the MPLS/GMPLS provider's network control messages and
some user requirements, cryptographic authentication of messages
without encryption of the contents of the message may provide
appropriate security. Using IPsec, authentication of messages is
provided by the Authentication Header (AH) or through the use of the
Encapsulating Security Protocol (ESP) with NULL encryption. Where
control messages require integrity but do not use IPsec, other
cryptographic authentication methods are often available. Message
authentication methods currently considered to be secure are based on
hashed message authentication codes (HMAC) [RFC2104] implemented with
a secure hash algorithm such as Secure Hash Algorithm 1 (SHA-1)
[RFC3174]. No attacks against HMAC SHA-1 are likely to play out in
the near future, but it is possible that people will soon find SHA-1
collisions. Thus, it is important that mechanisms be designed to be
flexible about the choice of hash functions and message integrity
checks. Also, many of these mechanisms do not include a convenient
way to manage and update keys.
A mechanism to provide a combination of confidentiality, data-origin
authentication, and connectionless integrity is the use of AES in GCM
(Counter with CBC-MAC) mode (RFC 4106) [RFC4106].
5.2.2. MPLS / GMPLS Diffserv and IPsec
MPLS and GMPLS, which provide differentiated services based on
traffic type, may encounter some conflicts with IPsec encryption of
traffic. Because encryption hides the content of the packets, it may
not be possible to differentiate the encrypted traffic in the same
manner as unencrypted traffic. Although Diffserv markings are copied
to the IPsec header and can provide some differentiation, not all
traffic types can be accommodated by this mechanism. Using IPsec
without IKE or IKEv2 (the better choice) is not advisable. IKEv2
provides IPsec Security Association creation and management, entity
authentication, key agreement, and key update. It works with a
variety of authentication methods including pre-shared keys, public
key certificates, and EAP. If DoS attacks against IKEv2 are
considered an important threat to mitigate, the cookie-based anti-
spoofing feature of IKEv2 should be used. IKEv2 has its own set of
cryptographic methods, but any of the default suites specified in
[RFC4308] or [RFC4869] provides more than adequate security.
5.2.3. Encryption for Device Configuration and Management
For configuration and management of MPLS/GMPLS devices, encryption
and authentication of the management connection at a level comparable
to that provided by IPsec is desirable.
Several methods of transporting MPLS/GMPLS device management traffic
offer authentication, integrity, and confidentiality.
- Secure Shell (SSH) offers protection for TELNET [STD8] or
terminal-like connections to allow device configuration.
- SNMPv3 [STD62] provides encrypted and authenticated protection for
SNMP-managed devices.
- Transport Layer Security (TLS) [RFC5246] and the closely-related
Secure Sockets Layer (SSL) are widely used for securing HTTP-based
communication, and thus can provide support for most XML- and
SOAP-based device management approaches.
- Since 2004, there has been extensive work proceeding in several
organizations (OASIS, W3C, WS-I, and others) on securing device
management traffic within a "Web Services" framework, using a wide
variety of security models, and providing support for multiple
security token formats, multiple trust domains, multiple signature
formats, and multiple encryption technologies.
- IPsec provides security services including integrity and
confidentiality at the network layer. With regards to device
management, its current use is primarily focused on in-band
management of user-managed IPsec gateway devices.
- There is recent work in the ISMS WG (Integrated Security Model for
SNMP Working Group) to define how to use SSH to secure SNMP, due
to the limited deployment of SNMPv3, and the possibility of using
Kerberos, particularly for interfaces like TELNET, where client
code exists.
5.2.4. Security Considerations for MPLS Pseudowires
In addition to IP traffic, MPLS networks may be used to transport
other services such as Ethernet, ATM, Frame Relay, and TDM. This is
done by setting up pseudowires (PWs) that tunnel the native service
through the MPLS core by encapsulating at the edges. The PWE
architecture is defined in [RFC3985].
PW tunnels may be set up using the PWE control protocol based on LDP
[RFC4447], and thus security considerations for LDP will most likely
be applicable to the PWE3 control protocol as well.
PW user packets contain at least one MPLS label (the PW label) and
may contain one or more MPLS tunnel labels. After the label stack,
there is a four-byte control word (which is optional for some PW
types), followed by the native service payload. It must be stressed
that encapsulation of MPLS PW packets in IP for the purpose of
enabling use of IPsec mechanisms is not a valid option.
The following is a non-exhaustive list of PW-specific threats:
- Unauthorized setup of a PW (e.g., to gain access to a customer
network)
- Unauthorized teardown of a PW (thus causing denial of service)
- Malicious reroute of a PW
- Unauthorized observation of PW packets
- Traffic analysis of PW connectivity
- Unauthorized insertion of PW packets
- Unauthorized modification of PW packets
- Unauthorized deletion of PW packets replay of PW packets
- Denial of service or significant impact on PW service quality
These threats are not mutually exclusive, for example, rerouting can
be used for snooping or insertion/deletion/replay, etc. Multisegment
PWs introduce additional weaknesses at their stitching points.
The PW user plane suffers from the following inherent security
weaknesses:
- Since the PW label is the only identifier in the packet, there is
no authenticatable source address.
- Since guessing a valid PW label is not difficult, it is relatively
easy to introduce seemingly valid foreign packets.
- Since the PW packet is not self-describing, minor modification of
control-plane packets renders the data-plane traffic useless.
- The control-word sequence number processing algorithm is
susceptible to a DoS attack.
The PWE control protocol introduces its own weaknesses:
- No (secure) peer autodiscovery technique has been standardized .
- PE authentication is not mandated, so an intruder can potentially
impersonate a PE; after impersonating a PE, unauthorized PWs may
be set up, consuming resources and perhaps allowing access to user
networks.
- Alternately, desired PWs may be torn down, giving rise to denial
of service.
The following characteristics of PWs can be considered security
strengths:
- The most obvious attacks require compromising edge or core routers
(although not necessarily those along the PW path).
- Adequate protection of the control-plane messaging is sufficient
to rule out many types of attacks.
- PEs are usually configured to reject MPLS packets from outside the
service provider network, thus ruling out insertion of PW packets
from the outside (since IP packets cannot masquerade as PW
packets).
5.2.5. End-to-End versus Hop-by-Hop Protection Tradeoffs in MPLS/GMPLS
In MPLS/GMPLS, cryptographic protection could potentially be applied
to the MPLS/GMPLS traffic at several different places. This section
discusses some of the tradeoffs in implementing encryption in several
different connection topologies among different devices within an
MPLS/GMPLS network.
Cryptographic protection typically involves a pair of devices that
protect the traffic passing between them. The devices may be
directly connected (over a single "hop"), or intervening devices may
transport the protected traffic between the pair of devices. The
extreme cases involve using protection between every adjacent pair of
devices along a given path (hop-by-hop), or using protection only
between the end devices along a given path (end-to-end). To keep
this discussion within the scope of this document, the latter ("end-
to-end") case considered here is CE-to-CE rather than fully end-to-
end.
Figure 3 depicts a simplified topology showing the Customer Edge (CE)
devices, the Provider Edge (PE) devices, and a variable number (three
are shown) of Provider core (P) devices, which might be present along
the path between two sites in a single VPN operated by a single
service provider (SP).
Site_1---CE---PE---P---P---P---PE---CE---Site_2
Figure 3: Simplified Topology Traversing through MPLS/GMPLS Core
Within this simplified topology, and assuming that the P devices are
not involved with cryptographic protection, four basic, feasible
configurations exist for protecting connections among the devices:
1) Site-to-site (CE-to-CE) - Apply confidentiality or integrity
services between the two CE devices, so that traffic will be
protected throughout the SP's network.
2) Provider edge-to-edge (PE-to-PE) - Apply confidentiality or
integrity services between the two PE devices. Unprotected
traffic is received at one PE from the customer's CE, then it is
protected for transmission through the SP's network to the other
PE, and finally it is decrypted or checked for integrity and sent
to the other CE.
3) Access link (CE-to-PE) - Apply confidentiality or integrity
services between the CE and PE on each side or on only one side.
4) Configurations 2 and 3 above can also be combined, with
confidentiality or integrity running from CE to PE, then PE to PE,
and then PE to CE.
Among the four feasible configurations, key tradeoffs in considering
encryption include:
- Vulnerability to link eavesdropping or tampering - assuming an
attacker can observe or modify data in transit on the links, would
it be protected by encryption?
- Vulnerability to device compromise - assuming an attacker can get
access to a device (or freely alter its configuration), would the
data be protected?
- Complexity of device configuration and management - given the
number of sites per VPN customer as Nce and the number of PEs
participating in a given VPN as Npe, how many device
configurations need to be created or maintained, and how do those
configurations scale?
- Processing load on devices - how many cryptographic operations
must be performed given N packets? - This raises considerations of
device capacity and perhaps end-to-end delay.
- Ability of the SP to provide enhanced services (QoS, firewall,
intrusion detection, etc.) - Can the SP inspect the data to
provide these services?
These tradeoffs are discussed for each configuration, below:
1) Site-to-site (CE-to-CE)
Link eavesdropping or tampering - protected on all links. Device
compromise - vulnerable to CE compromise.
Complexity - single administration, responsible for one device per
site (Nce devices), but overall configuration per VPN scales as
Nce**2.
Though the complexity may be reduced: 1) In practice, as Nce
grows, the number of VPNs falls off from being a full clique;
2) If the CEs run an automated key management protocol, then
they should be able to set up and tear down secured VPNs
without any intervention.
Processing load - on each of the two CEs, each packet is
cryptographically processed (2P), though the protection may be
"integrity check only" or "integrity check plus encryption."
Enhanced services - severely limited; typically only Diffserv
markings are visible to the SP, allowing some QoS services.
The CEs could also use the IPv6 Flow Label to identify traffic
classes.
2) Provider Edge-to-Edge (PE-to-PE)
Link eavesdropping or tampering - vulnerable on CE-PE links;
protected on SP's network links.
Device compromise - vulnerable to CE or PE compromise.
Complexity - single administration, Npe devices to configure.
(Multiple sites may share a PE device so Npe is typically much
smaller than Nce.) Scalability of the overall configuration
depends on the PPVPN type: if the cryptographic protection is
separate per VPN context, it scales as Npe**2 per customer VPN.
If it is per-PE, it scales as Npe**2 for all customer VPNs
combined.
Processing load - on each of the two PEs, each packet is
cryptographically processed (2P).
Enhanced services - full; SP can apply any enhancements based on
detailed view of traffic.
3) Access Link (CE-to-PE)
Link eavesdropping or tampering - protected on CE-PE link;
vulnerable on SP's network links.
Device compromise - vulnerable to CE or PE compromise.
Complexity - two administrations (customer and SP) with device
configuration on each side (Nce + Npe devices to configure),
but because there is no mesh, the overall configuration scales
as Nce.
Processing load - on each of the two CEs, each packet is
cryptographically processed, plus on each of the two PEs, each
packet is cryptographically processed (4P).
Enhanced services - full; SP can apply any enhancements based on a
detailed view of traffic.
4) Combined Access link and PE-to-PE (essentially hop-by-hop).
Link eavesdropping or tampering - protected on all links.
Device compromise - vulnerable to CE or PE compromise.
Complexity - two administrations (customer and SP) with device
configuration on each side (Nce + Npe devices to configure).
Scalability of the overall configuration depends on the PPVPN
type: If the cryptographic processing is separate per VPN
context, it scales as Npe**2 per customer VPN. If it is per-
PE, it scales as Npe**2 for all customer VPNs combined.
Processing load - on each of the two CEs, each packet is
cryptographically processed, plus on each of the two PEs, each
packet is cryptographically processed twice (6P).
Enhanced services - full; SP can apply any enhancements based on a
detailed view of traffic.
Given the tradeoffs discussed above, a few conclusions can be drawn:
- Configurations 2 and 3 are subsets of 4 that may be appropriate
alternatives to 4 under certain threat models; the remainder of
these conclusions compare 1 (CE-to-CE) versus 4 (combined access
links and PE-to-PE).
- If protection from link eavesdropping or tampering is all that is
important, then configurations 1 and 4 are equivalent.
- If protection from device compromise is most important and the
threat is to the CE devices, both cases are equivalent; if the
threat is to the PE devices, configuration 1 is better.
- If reducing complexity is most important, and the size of the
network is small, configuration 1 is better. Otherwise,
configuration 4 is better because rather than a mesh of CE
devices, it requires a smaller mesh of PE devices. Also, under
some PPVPN approaches, the scaling of 4 is further improved by
sharing the same PE-PE mesh across all VPN contexts. The scaling
advantage of 4 may be increased or decreased in any given
situation if the CE devices are simpler to configure than the PE
devices, or vice-versa.
- If the overall processing load is a key factor, then 1 is better,
unless the PEs come with a hardware encryption accelerator and the
CEs do not.
- If the availability of enhanced services support from the SP is
most important, then 4 is best.
- If users are concerned with having their VPNs misconnected with
other users' VPNs, then encryption with 1 can provide protection.
As a quick overall conclusion, CE-to-CE protection is better against
device compromise, but this comes at the cost of enhanced services
and at the cost of operational complexity due to the Order(n**2)
scaling of a larger mesh.
This analysis of site-to-site vs. hop-by-hop tradeoffs does not
explicitly include cases of multiple providers cooperating to provide
a PPVPN service, public Internet VPN connectivity, or remote access
VPN service, but many of the tradeoffs are similar.
In addition to the simplified models, the following should also be
considered:
- There are reasons, perhaps, to protect a specific P-to-P or PE-
to-P.
- There may be reasons to do multiple encryptions over certain
segments. One may be using an encrypted wireless link under our
IPsec VPN to access an SSL-secured web site to download encrypted
email attachments: four layers.)
- It may be appropriate that, for example, cryptographic integrity
checks are applied end to end, and confidentiality is applied over
a shorter span.
- Different cryptographic protection may be required for control
protocols and data traffic.
- Attention needs to be given to how auxiliary traffic is protected,
e.g., the ICMPv6 packets that flow back during PMTU discovery,
among other examples.
5.3. Access Control Techniques
Access control techniques include packet-by-packet or packet-flow-
by-packet-flow access control by means of filters and firewalls on
IPv4/IPv6 packets, as well as by means of admitting a "session" for a
control, signaling, or management protocol. Enforcement of access
control by isolated infrastructure addresses is discussed in Section
5.4 of this document.
In this document, we distinguish between filtering and firewalls
based primarily on the direction of traffic flow. We define
filtering as being applicable to unidirectional traffic, while a
firewall can analyze and control both sides of a conversation.
The definition has two significant corollaries:
- Routing or traffic flow symmetry: A firewall typically requires
routing symmetry, which is usually enforced by locating a firewall
where the network topology assures that both sides of a
conversation will pass through the firewall. A filter can operate
upon traffic flowing in one direction, without considering traffic
in the reverse direction. Beware that this concept could result
in a single point of failure.
- Statefulness: Because it receives both sides of a conversation, a
firewall may be able to interpret a significant amount of
information concerning the state of that conversation and use this
information to control access. A filter can maintain some limited
state information on a unidirectional flow of packets, but cannot
determine the state of the bidirectional conversation as precisely
as a firewall.
For a general description on filtering and rate limiting for IP
networks, please also see [OPSEC-FILTER].
5.3.1. Filtering
It is relatively common for routers to filter packets. That is,
routers can look for particular values in certain fields of the IP or
higher-level (e.g., TCP or UDP) headers. Packets matching the
criteria associated with a particular filter may either be discarded
or given special treatment. Today, not only routers, but most end
hosts have filters, and every instance of IPsec is also a filter
[RFC4301].
In discussing filters, it is useful to separate the filter
characteristics that may be used to determine whether a packet
matches a filter from the packet actions applied to those packets
matching a particular filter.
o Filter Characteristics
Filter characteristics or rules are used to determine whether a
particular packet or set of packets matches a particular filter.
In many cases, filter characteristics may be stateless. A stateless
filter determines whether a particular packet matches a filter based
solely on the filter definition, normal forwarding information (such
as the next hop for a packet), the interface on which a packet
arrived, and the contents of that individual packet. Typically,
stateless filters may consider the incoming and outgoing logical or
physical interface, information in the IP header, and information in
higher-layer headers such as the TCP or UDP header. Information in
the IP header to be considered may for example include source and
destination IP addresses; Protocol field, Fragment Offset, and TOS
field in IPv4; or Next Header, Extension Headers, Flow label, etc. in
IPv6. Filters also may consider fields in the TCP or UDP header such
as the Port numbers, the SYN field in the TCP header, as well as ICMP
and ICMPv6 type.
Stateful filtering maintains packet-specific state information to aid
in determining whether a filter rule has been met. For example, a
device might apply stateless filtering to the first fragment of a
fragmented IPv4 packet. If the filter matches, then the data unit ID
may be remembered and other fragments of the same packet may then be
considered to match the same filter. Stateful filtering is more
commonly done in firewalls, although firewall technology may be added
to routers. The data unit ID can also be a Fragment Extension Header
Identification field in IPv6.
o Actions based on Filter Results
If a packet, or a series of packets, matches a specific filter, then
a variety of actions may be taken based on that match. Examples of
such actions include:
- Discard
In many cases, filters are set to catch certain undesirable
packets. Examples may include packets with forged or invalid
source addresses, packets that are part of a DoS or Distributed
DoS (DDoS) attack, or packets trying to access unallowed
resources (such as network management packets from an
unauthorized source). Where such filters are activated, it is
common to discard the packet or set of packets matching the
filter silently. The discarded packets may of course also be
counted or logged.
- Set CoS
A filter may be used to set the class of service associated
with the packet.
- Count packets or bytes
- Rate Limit
In some cases, the set of packets matching a particular filter
may be limited to a specified bandwidth. In this case, packets
or bytes would be counted, and would be forwarded normally up
to the specified limit. Excess packets may be discarded or may
be marked (for example, by setting a "discard eligible" bit in
the IPv4 ToS field, or changing the EXP value to identify
traffic as being out of contract).
- Forward and Copy
It is useful in some cases to forward some set of packets
normally, but also to send a copy to a specified other address
or interface. For example, this may be used to implement a
lawful intercept capability or to feed selected packets to an
Intrusion Detection System.
o Other Packet Filters Issues
Filtering performance may vary widely according to implementation and
the types and number of rules. Without acceptable performance,
filtering is not useful.
The precise definition of "acceptable" may vary from SP to SP, and
may depend upon the intended use of the filters. For example, for
some uses, a filter may be turned on all the time to set CoS, to
prevent an attack, or to mitigate the effect of a possible future
attack. In this case, it is likely that the SP will want the filter
to have minimal or no impact on performance. In other cases, a
filter may be turned on only in response to a major attack (such as a
major DDoS attack). In this case, a greater performance impact may
be acceptable to some service providers.
A key consideration with the use of packet filters is that they can
provide few options for filtering packets carrying encrypted data.
Because the data itself is not accessible, only packet header
information or other unencrypted fields can be used for filtering.
5.3.2. Firewalls
Firewalls provide a mechanism for controlling traffic passing between
different trusted zones in the MPLS/GMPLS model or between a trusted
zone and an untrusted zone. Firewalls typically provide much more
functionality than filters, because they may be able to apply
detailed analysis and logical functions to flows, and not just to
individual packets. They may offer a variety of complex services,
such as threshold-driven DoS attack protection, virus scanning,
acting as a TCP connection proxy, etc.
As with other access control techniques, the value of firewalls
depends on a clear understanding of the topologies of the MPLS/GMPLS
core network, the user networks, and the threat model. Their
effectiveness depends on a topology with a clearly defined inside
(secure) and outside (not secure).
Firewalls may be applied to help protect MPLS/GMPLS core network
functions from attacks originating from the Internet or from
MPLS/GMPLS user sites, but typically other defensive techniques will
be used for this purpose.
Where firewalls are employed as a service to protect user VPN sites
from the Internet, different VPN users, and even different sites of a
single VPN user, may have varying firewall requirements. The overall
PPVPN logical and physical topology, along with the capabilities of
the devices implementing the firewall services, has a significant
effect on the feasibility and manageability of such varied firewall
service offerings.
Another consideration with the use of firewalls is that they can
provide few options for handling packets carrying encrypted data.
Because the data itself is not accessible, only packet header
information, other unencrypted fields, or analysis of the flow of
encrypted packets can be used for making decisions on accepting or
rejecting encrypted traffic.
Two approaches of using firewalls are to move the firewall outside of
the encrypted part of the path or to register and pre-approve the
encrypted session with the firewall.
Handling DoS attacks has become increasingly important. Useful
guidelines include the following:
1. Perform ingress filtering everywhere.
2. Be able to filter DoS attack packets at line speed.
3. Do not allow oneself to amplify attacks.
4. Continue processing legitimate traffic. Over provide for heavy
loads. Use diverse locations, technologies, etc.
5.3.3. Access Control to Management Interfaces
Most of the security issues related to management interfaces can be
addressed through the use of authentication techniques as described
in the section on authentication (Section 5.1). However, additional
security may be provided by controlling access to management
interfaces in other ways.
The Optical Internetworking Forum has done relevant work on
protecting such interfaces with TLS, SSH, Kerberos, IPsec, WSS, etc.
See "Security for Management Interfaces to Network Elements"
[OIF-SMI-01.0] and "Addendum to the Security for Management
Interfaces to Network Elements" [OIF-SMI-02.1]. See also the work in
the ISMS WG (http://datatracker.ietf.org/wg/isms/charter/).
Management interfaces, especially console ports on MPLS/GMPLS
devices, may be configured so they are only accessible out-of-band,
through a system that is physically or logically separated from the
rest of the MPLS/GMPLS infrastructure.
Where management interfaces are accessible in-band within the
MPLS/GMPLS domain, filtering or firewalling techniques can be used to
restrict unauthorized in-band traffic from having access to
management interfaces. Depending on device capabilities, these
filtering or firewalling techniques can be configured either on other
devices through which the traffic might pass, or on the individual
MPLS/GMPLS devices themselves.
5.4. Use of Isolated Infrastructure
One way to protect the infrastructure used for support of MPLS/GMPLS
is to separate the resources for support of MPLS/GMPLS services from
the resources used for other purposes (such as support of Internet
services). In some cases, this may involve using physically separate
equipment for VPN services, or even a physically separate network.
For example, PE-based IPVPNs may be run on a separate backbone not
connected to the Internet, or may use separate edge routers from
those supporting Internet service. Private IPv4 addresses (local to
the provider and non-routable over the Internet) are sometimes used
to provide additional separation. For a discussion of comparable
techniques for IPv6, see "Local Network Protection for IPv6," RFC
4864 [RFC4864].
In a GMPLS network, it is possible to operate the control plane using
physically separate resources from those used for the data plane.
This means that the data-plane resources can be physically protected
and isolated from other equipment to protect users' data while the
control and management traffic uses network resources that can be
accessed by operators to configure the network. Conversely, the
separation of control and data traffic may lead the operator to
consider that the network is secure because the data-plane resources
are physically secure. However, this is not the case if the control
plane can be attacked through a shared or open network, and control-
plane protection techniques must still be applied.
5.5. Use of Aggregated Infrastructure
In general, it is not feasible to use a completely separate set of
resources for support of each service. In fact, one of the main
reasons for MPLS/GMPLS enabled services is to allow sharing of
resources between multiple services and multiple users. Thus, even
if certain services use a separate network from Internet services,
nonetheless there will still be multiple MPLS/GMPLS users sharing the
same network resources. In some cases, MPLS/GMPLS services will
share network resources with Internet services or other services.
It is therefore important for MPLS/GMPLS services to provide
protection between resources used by different parties. Thus, a
well-behaved MPLS/GMPLS user should be protected from possible
misbehavior by other users. This requires several security
measurements to be implemented. Resource limits can be placed on a
per service and per user basis. Possibilities include, for example,
using a virtual router or logical router to define hardware or
software resource limits per service or per individual user; using
rate limiting per Virtual Routing and Forwarding (VRF) or per
Internet connection to provide bandwidth protection; or using
resource reservation for control-plane traffic. In addition to
bandwidth protection, separate resource allocation can be used to
limit security attacks only to directly impacted service(s) or
customer(s). Strict, separate, and clearly defined engineering rules
and provisioning procedures can reduce the risks of network-wide
impact of a control-plane attack, DoS attack, or misconfiguration.
In general, the use of aggregated infrastructure allows the service
provider to benefit from stochastic multiplexing of multiple bursty
flows, and also may in some cases thwart traffic pattern analysis by
combining the data from multiple users. However, service providers
must minimize security risks introduced from any individual service
or individual users.
5.6. Service Provider Quality Control Processes
Deployment of provider-provisioned VPN services in general requires a
relatively large amount of configuration by the SP. For example, the
SP needs to configure which VPN each site belongs to, as well as QoS
and SLA guarantees. This large amount of required configuration
leads to the possibility of misconfiguration.
It is important for the SP to have operational processes in place to
reduce the potential impact of misconfiguration. CE-to-CE
authentication may also be used to detect misconfiguration when it
occurs. CE-to-CE encryption may also limit the damage when
misconfiguration occurs.
5.7. Deployment of Testable MPLS/GMPLS Service
This refers to solutions that can be readily tested to make sure they
are configured correctly. For example, for a point-to-point
connection, checking that the intended connectivity is working pretty
much ensures that there is no unintended connectivity to some other
site.
5.8. Verification of Connectivity
In order to protect against deliberate or accidental misconnection,
mechanisms can be put in place to verify both end-to-end connectivity
and hop-by-hop resources. These mechanisms can trace the routes of
LSPs in both the control plane and the data plane.
It should be noted that if there is an attack on the control plane,
data-plane connectivity test mechanisms that rely on the control
plane can also be attacked. This may hide faults through false
positives or disrupt functioning services through false negatives.
6. Monitoring, Detection, and Reporting of Security Attacks
MPLS/GMPLS network and service may be subject to attacks from a
variety of security threats. Many threats are described in Section 4
of this document. Many of the defensive techniques described in this
document and elsewhere provide significant levels of protection from
a variety of threats. However, in addition to employing defensive
techniques silently to protect against attacks, MPLS/GMPLS services
can also add value for both providers and customers by implementing
security monitoring systems to detect and report on any security
attacks, regardless of whether the attacks are effective.
Attackers often begin by probing and analyzing defenses, so systems
that can detect and properly report these early stages of attacks can
provide significant benefits.
Information concerning attack incidents, especially if available
quickly, can be useful in defending against further attacks. It can
be used to help identify attackers or their specific targets at an
early stage. This knowledge about attackers and targets can be used
to strengthen defenses against specific attacks or attackers, or to
improve the defenses for specific targets on an as-needed basis.
Information collected on attacks may also be useful in identifying
and developing defenses against novel attack types.
Monitoring systems used to detect security attacks in MPLS/GMPLS
typically operate by collecting information from the Provider Edge
(PE), Customer Edge (CE), and/or Provider backbone (P) devices.
Security monitoring systems should have the ability to actively
retrieve information from devices (e.g., SNMP get) or to passively
receive reports from devices (e.g., SNMP notifications). The systems
may actively retrieve information from devices (e.g., SNMP get) or
passively receive reports from devices (e.g., SNMP notifications).
The specific information exchanged depends on the capabilities of the
devices and on the type of VPN technology. Particular care should be
given to securing the communications channel between the monitoring
systems and the MPLS/GMPLS devices.
The CE, PE, and P devices should employ efficient methods to acquire
and communicate the information needed by the security monitoring
systems. It is important that the communication method between
MPLS/GMPLS devices and security monitoring systems be designed so
that it will not disrupt network operations. As an example, multiple
attack events may be reported through a single message, rather than
allowing each attack event to trigger a separate message, which might
result in a flood of messages, essentially becoming a DoS attack
against the monitoring system or the network.
The mechanisms for reporting security attacks should be flexible
enough to meet the needs of MPLS/GMPLS service providers, MPLS/GMPLS
customers, and regulatory agencies, if applicable. The specific
reports should depend on the capabilities of the devices, the
security monitoring system, the type of VPN, and the service level
agreements between the provider and customer.
While SNMP/syslog type monitoring and detection mechanisms can detect
some attacks (usually resulting from flapping protocol adjacencies,
CPU overload scenarios, etc.), other techniques, such as netflow-
based traffic fingerprinting, are needed for more detailed detection
and reporting.
With netflow-based traffic fingerprinting, each packet that is
forwarded within a device is examined for a set of IP packet
attributes. These attributes are the IP packet identity or
fingerprint of the packet and determine if the packet is unique or
similar to other packets.
The flow information is extremely useful for understanding network
behavior, and detecting and reporting security attacks:
- Source address allows the understanding of who is originating the
traffic.
- Destination address tells who is receiving the traffic.
- Ports characterize the application utilizing the traffic.
- Class of service examines the priority of the traffic.
- The device interface tells how traffic is being utilized by the
network device.
- Tallied packets and bytes show the amount of traffic.
- Flow timestamps allow the understanding of the life of a flow;
timestamps are useful for calculating packets and bytes per
second.
- Next-hop IP addresses including BGP routing Autonomous Systems
(ASes).
- Subnet mask for the source and destination addresses are for
calculating prefixes.
- TCP flags are useful for examining TCP handshakes.
7. Service Provider General Security Requirements
This section covers security requirements the provider may have for
securing its MPLS/GMPLS network infrastructure including LDP and
RSVP-TE-specific requirements.
The MPLS/GMPLS service provider's requirements defined here are for
the MPLS/GMPLS core in the reference model. The core network can be
implemented with different types of network technologies, and each
core network may use different technologies to provide the various
services to users with different levels of offered security.
Therefore, an MPLS/GMPLS service provider may fulfill any number of
the security requirements listed in this section. This document does
not state that an MPLS/GMPLS network must fulfill all of these
requirements to be secure.
These requirements are focused on: 1) how to protect the MPLS/GMPLS
core from various attacks originating outside the core including
those from network users, both accidentally and maliciously, and 2)
how to protect the end users.
7.1. Protection within the Core Network
7.1.1. Control-Plane Protection - General
- Filtering spoofed infrastructure IP addresses at edges
Many attacks on protocols running in a core involve spoofing a source
IP address of a node in the core (e.g., TCP-RST attacks). It makes
sense to apply anti-spoofing filtering at edges, e.g., using strict
unicast reverse path forwarding (uRPF) [RFC3704] and/or by preventing
the use of infrastructure addresses as source. If this is done
comprehensively, the need to cryptographically secure these protocols
is smaller. See [BACKBONE-ATTKS] for more elaborate description.
- Protocol authentication within the core
The network infrastructure must support mechanisms for authentication
of the control-plane messages. If an MPLS/GMPLS core is used, LDP
sessions may be authenticated with TCP MD5. In addition, IGP and BGP
authentication should be considered. For a core providing various
IP, VPN, or transport services, PE-to-PE authentication may also be
performed via IPsec. See the above discussion of protocol security
services: authentication, integrity (with replay detection), and
confidentiality. Protocols need to provide a complete set of
security services from which the SP can choose. Also, the important
but often more difficult part is key management. Considerations,
guidelines, and strategies regarding key management are discussed in
[RFC3562], [RFC4107], [RFC4808].
With today's processors, applying cryptographic authentication to the
control plane may not increase the cost of deployment for providers
significantly, and will help to improve the security of the core. If
the core is dedicated to MPLS/GMPLS enabled services without any
interconnects to third parties, then this may reduce the requirement
for authentication of the core control plane.
- Infrastructure Hiding
Here we discuss means to hide the provider's infrastructure nodes.
An MPLS/GMPLS provider may make its infrastructure routers (P and PE)
unreachable from outside users and unauthorized internal users. For
example, separate address space may be used for the infrastructure
loopbacks.
Normal TTL propagation may be altered to make the backbone look like
one hop from the outside, but caution needs to be taken for loop
prevention. This prevents the backbone addresses from being exposed
through trace route; however, this must also be assessed against
operational requirements for end-to-end fault tracing.
An Internet backbone core may be re-engineered to make Internet
routing an edge function, for example, by using MPLS label switching
for all traffic within the core and possibly making the Internet a
VPN within the PPVPN core itself. This helps to detach Internet
access from PPVPN services.
Separating control-plane, data-plane, and management-plane
functionality in hardware and software may be implemented on the PE
devices to improve security. This may help to limit the problems
when attacked in one particular area, and may allow each plane to
implement additional security measures separately.
PEs are often more vulnerable to attack than P routers, because PEs
cannot be made unreachable from outside users by their very nature.
Access to core trunk resources can be controlled on a per-user basis
by using of inbound rate limiting or traffic shaping; this can be
further enhanced on a per-class-of-service basis (see Section 8.2.3)
In the PE, using separate routing processes for different services,
for example, Internet and PPVPN service, may help to improve the
PPVPN security and better protect VPN customers. Furthermore, if
resources, such as CPU and memory, can be further separated based on
applications, or even individual VPNs, it may help to provide
improved security and reliability to individual VPN customers.
7.1.2. Control-Plane Protection with RSVP-TE
- General RSVP Security Tools
Isolation of the trusted domain is an important security mechanism
for RSVP, to ensure that an untrusted element cannot access a router
of the trusted domain. However, ASBR-ASBR communication for inter-AS
LSPs needs to be secured specifically. Isolation mechanisms might
also be bypassed by an IPv4 Router Alert or IPv6 using Next Header 0
packets. A solution could consist of disabling the processing of IP
options. This drops or ignores all IP packets with IPv4 options,
including the router alert option used by RSVP; however, this may
have an impact on other protocols using IPv4 options. An alternative
is to configure access-lists on all incoming interfaces dropping IPv4
protocol or IPv6 next header 46 (RSVP).
RSVP security can be strengthened by deactivating RSVP on interfaces
with neighbors who are not authorized to use RSVP, to protect against
adjacent CE-PE attacks. However, this does not really protect
against DoS attacks or attacks on non-adjacent routers. It has been
demonstrated that substantial CPU resources are consumed simply by
processing received RSVP packets, even if the RSVP process is
deactivated for the specific interface on which the RSVP packets are
received.
RSVP neighbor filtering at the protocol level, to restrict the set of
neighbors that can send RSVP messages to a given router, protects
against non-adjacent attacks. However, this does not protect against
DoS attacks and does not effectively protect against spoofing of the
source address of RSVP packets, if the filter relies on the
neighbor's address within the RSVP message.
RSVP neighbor filtering at the data-plane level, with an access list
to accept IP packets with port 46 only for specific neighbors,
requires Router Alert mode to be deactivated and does not protect
against spoofing.
Another valuable tool is RSVP message pacing, to limit the number of
RSVP messages sent to a given neighbor during a given period. This
allows blocking DoS attack propagation.
- Another approach is to limit the impact of an attack on control-
plane resources.
To ensure continued effective operation of the MPLS router even in
the case of an attack that bypasses packet filtering mechanisms such
as Access Control Lists in the data plane, it is important that
routers have some mechanisms to limit the impact of the attack.
There should be a mechanism to rate limit the amount of control-plane
traffic addressed to the router, per interface. This should be
configurable on a per-protocol basis, (and, ideally, on a per-sender
basis) to avoid letting an attacked protocol or a given sender block
all communications. This requires the ability to filter and limit
the rate of incoming messages of particular protocols, such as RSVP
(filtering at the IP protocol level), and particular senders. In
addition, there should be a mechanism to limit CPU and memory
capacity allocated to RSVP, so as to protect other control-plane
elements. To limit memory allocation, it will probably be necessary
to limit the number of LSPs that can be set up.
- Authentication for RSVP messages
RSVP message authentication is described in RFC 2747 [RFC2747] and
RFC 3097 [RFC3097]. It is one of the most powerful tools for
protection against RSVP-based attacks. It applies cryptographic
authentication to RSVP messages based on a secure message hash using
a key shared by RSVP neighbors. This protects against LSP creation
attacks, at the expense of consuming significant CPU resources for
digest computation. In addition, if the neighboring RSVP speaker is
compromised, it could be used to launch attacks using authenticated
RSVP messages. These methods, and certain other aspects of RSVP
security, are explained in detail in RFC 4230 [RFC4230]. Key
management must be implemented. Logging and auditing as well as
multiple layers of cryptographic protection can help here. IPsec can
also be used in some cases (see [RFC4230]).
One challenge using RSVP message authentication arises in many cases
where non-RSVP nodes are present in the network. In such cases, the
RSVP neighbor may not be known up front, thus neighbor-based keying
approaches fail, unless the same key is used everywhere, which is not
recommended for security reasons. Group keying may help in such
cases. The security properties of various keying approaches are
discussed in detail in [RSVP-key].
7.1.3. Control-Plane Protection with LDP
The approaches to protect MPLS routers against LDP-based attacks are
similar to those for RSVP, including isolation, protocol deactivation
on specific interfaces, filtering of LDP neighbors at the protocol
level, filtering of LDP neighbors at the data-plane level (with an
access list that filters the TCP and UDP LDP ports), authentication
with a message digest, rate limiting of LDP messages per protocol per
sender, and limiting all resources allocated to LDP-related tasks.
LDP protection could be considered easier in a certain sense. UDP
port matching may be sufficient for LDP protection. Router alter
options and beyond might be involved in RSVP protection.
7.1.4. Data-Plane Protection
IPsec can provide authentication, integrity, confidentiality, and
replay detection for provider or user data. It also has an
associated key management protocol.
In today's MPLS/GMPLS, ATM, or Frame Relay networks, encryption is
not provided as a basic feature. Mechanisms described in Section 5
can be used to secure the MPLS data-plane traffic carried over an
MPLS core. Both the Frame Relay Forum and the ATM Forum standardized
cryptographic security services in the late 1990s, but these
standards are not widely implemented.
7.2. Protection on the User Access Link
Peer or neighbor protocol authentication may be used to enhance
security. For example, BGP MD5 authentication may be used to enhance
security on PE-CE links using eBGP. In the case of inter-provider
connections, cryptographic protection mechanisms, such as IPsec, may
be used between ASes.
If multiple services are provided on the same PE platform, different
WAN address spaces may be used for different services (e.g., VPN and
non-VPN) to enhance isolation.
Firewall and Filtering: access control mechanisms can be used to
filter any packets destined for the service provider's infrastructure
prefix or eliminate routes identified as illegitimate. Filtering
should also be applied to prevent sourcing packets with
infrastructure IP addresses from outside.
Rate limiting may be applied to the user interface/logical interfaces
as a defense against DDoS bandwidth attack. This is helpful when the
PE device is supporting both multiple services, especially VPN and
Internet Services, on the same physical interfaces through different
logical interfaces.
7.2.1. Link Authentication
Authentication can be used to validate site access to the network via
fixed or logical connections, e.g., L2TP or IPsec, respectively. If
the user wishes to hold the authentication credentials for access,
then provider solutions require the flexibility for either direct
authentication by the PE itself or interaction with a customer
authentication server. Mechanisms are required in the latter case to
ensure that the interaction between the PE and the customer
authentication server is appropriately secured.
7.2.2. Access Routing Control
Choice of routing protocols, e.g., RIP, OSPF, or BGP, may be used to
provide control access between a CE and a PE. Per-neighbor and per-
VPN routing policies may be established to enhance security and
reduce the impact of a malicious or non-malicious attack on the PE;
the following mechanisms, in particular, should be considered:
- Limiting the number of prefixes that may be advertised on a per-
access basis into the PE. Appropriate action may be taken should
a limit be exceeded, e.g., the PE shutting down the peer session
to the CE
- Applying route dampening at the PE on received routing updates
- Definition of a per-VPN prefix limit after which additional
prefixes will not be added to the VPN routing table.
In the case of inter-provider connection, access protection, link
authentication, and routing policies as described above may be
applied. Both inbound and outbound firewall or filtering mechanisms
between ASes may be applied. Proper security procedures must be
implemented in inter-provider interconnection to protect the
providers' network infrastructure and their customers. This may be
custom designed for each inter-provider peering connection, and must
be agreed upon by both providers.
7.2.3. Access QoS
MPLS/GMPLS providers offering QoS-enabled services require mechanisms
to ensure that individual accesses are validated against their
subscribed QoS profile and as such gain access to core resources that
match their service profile. Mechanisms such as per-class-of-service
rate limiting or traffic shaping on ingress to the MPLS/GMPLS core
are two options for providing this level of control. Such mechanisms
may require the per-class-of-service profile to be enforced either by
marking, remarking, or discarding of traffic outside of the profile.
7.2.4. Customer Service Monitoring Tools
End users needing specific statistics on the core, e.g., routing
table, interface status, or QoS statistics, place requirements on
mechanisms at the PE both to validate the incoming user and limit the
views available to that particular user. Mechanisms should also be
considered to ensure that such access cannot be used as means to
construct a DoS attack (either maliciously or accidentally) on the PE
itself. This could be accomplished either through separation of
these resources within the PE itself or via the capability to rate
limiting, which is performed on the basis of each physical interface
or each logical connection.
7.3. General User Requirements for MPLS/GMPLS Providers
MPLS/GMPLS providers must support end users' security requirements.
Depending on the technologies used, these requirements may include:
- User control plane separation through routing isolation when
applicable, for example, in the case of MPLS VPNs.
- Protection against intrusion, DoS attacks, and spoofing
- Access Authentication
- Techniques highlighted throughout this document that identify
methodologies for the protection of resources and the MPLS/GMPLS
infrastructure.
Hardware or software errors in equipment leading to breaches in
security are not within the scope of this document.
8. Inter-Provider Security Requirements
This section discusses security capabilities that are important at
the MPLS/GMPLS inter-provider connections and at devices (including
ASBR routers) supporting these connections. The security
capabilities stated in this section should be considered as
complementary to security considerations addressed in individual
protocol specifications or security frameworks.
Security vulnerabilities and exposures may be propagated across
multiple networks because of security vulnerabilities arising in one
peer's network. Threats to security originate from accidental,
administrative, and intentional sources. Intentional threats include
events such as spoofing and denial-of-service (DoS) attacks.
The level and nature of threats, as well as security and availability
requirements, may vary over time and from network to network. This
section, therefore, discusses capabilities that need to be available
in equipment deployed for support of the MPLS InterCarrier
Interconnect (MPLS-ICI). Whether any particular capability is used
in any one specific instance of the ICI is up to the service
providers managing the PE equipment offering or using the ICI
services.
8.1. Control-Plane Protection
This section discusses capabilities for control-plane protection,
including protection of routing, signaling, and OAM capabilities.
8.1.1. Authentication of Signaling Sessions
Authentication may be needed for signaling sessions (i.e., BGP, LDP,
and RSVP-TE) and routing sessions (e.g., BGP), as well as OAM
sessions across domain boundaries. Equipment must be able to support
the exchange of all protocol messages over IPsec ESP, with NULL
encryption and authentication, between the peering ASBRs. Support
for message authentication for LDP, BGP, and RSVP-TE authentication
must also be provided. Manual keying of IPsec should not be used.
IKEv2 with pre-shared secrets or public key methods should be used.
Replay detection should be used.
Mechanisms to authenticate and validate a dynamic setup request must
be available. For instance, if dynamic signaling of a TE-LSP or PW
is crossing a domain boundary, there must be a way to detect whether
the LSP source is who it claims to be and that it is allowed to
connect to the destination.
Message authentication support for all TCP-based protocols within the
scope of the MPLS-ICI (i.e., LDP signaling and BGP routing) and
Message authentication with the RSVP-TE Integrity Object must be
provided to interoperate with current practices. Equipment should be
able to support the exchange of all signaling and routing (LDP, RSVP-
TE, and BGP) protocol messages over a single IPsec association pair
in tunnel or transport mode with authentication but with NULL
encryption, between the peering ASBRs. IPsec, if supported, must be
supported with HMAC-SHA-1 and alternatively with HMAC-SHA-2 and
optionally SHA-1. It is expected that authentication algorithms will
evolve over time and support can be updated as needed.
OAM operations across the MPLS-ICI could also be the source of
security threats on the provider infrastructure as well as the
service offered over the MPLS-ICI. A large volume of OAM messages
could overwhelm the processing capabilities of an ASBR if the ASBR is
not properly protected. Maliciously generated OAM messages could
also be used to bring down an otherwise healthy service (e.g., MPLS
Pseudowire), and therefore affect service security. LSP ping does
not support authentication today, and that support should be a
subject for future consideration. Bidirectional Forwarding Detection
(BFD), however, does have support for carrying an authentication
object. It also supports Time-To-Live (TTL) processing as an anti-
replay measure. Implementations conformant with this MPLS-ICI should
support BFD authentication and must support the procedures for TTL
processing.
8.1.2. Protection Against DoS Attacks in the Control Plane
Implementations must have the ability to prevent signaling and
routing DoS attacks on the control plane per interface and provider.
Such prevention may be provided by rate limiting signaling and
routing messages that can be sent by a peer provider according to a
traffic profile and by guarding against malformed packets.
Equipment must provide the ability to filter signaling, routing, and
OAM packets destined for the device, and must provide the ability to
rate limit such packets. Packet filters should be capable of being
separately applied per interface, and should have minimal or no
performance impact. For example, this allows an operator to filter
or rate limit signaling, routing, and OAM messages that can be sent
by a peer provider and limit such traffic to a given profile.
During a control-plane DoS attack against an ASBR, the router should
guarantee sufficient resources to allow network operators to execute
network management commands to take corrective action, such as
turning on additional filters or disconnecting an interface under
attack. DoS attacks on the control plane should not adversely affect
data-plane performance.
Equipment running BGP must support the ability to limit the number of
BGP routes received from any particular peer. Furthermore, in the
case of IPVPN, a router must be able to limit the number of routes
learned from a BGP peer per IPVPN. In the case that a device has
multiple BGP peers, it should be possible for the limit to vary
between peers.
8.1.3. Protection against Malformed Packets
Equipment should be robust in the presence of malformed protocol
packets. For example, malformed routing, signaling, and OAM packets
should be treated in accordance with the relevant protocol
specification.
8.1.4. Ability to Enable/Disable Specific Protocols
Equipment must have the ability to drop any signaling or routing
protocol messages when these messages are to be processed by the ASBR
but the corresponding protocol is not enabled on that interface.
Equipment must allow an administrator to enable or disable a protocol
(by default, the protocol is disabled unless administratively
enabled) on an interface basis.
Equipment must be able to drop any signaling or routing protocol
messages when these messages are to be processed by the ASBR but the
corresponding protocol is not enabled on that interface. This
dropping should not adversely affect data-plane or control-plane
performance.
8.1.5. Protection against Incorrect Cross Connection
The capability to detect and locate faults in an LSP cross-connect
must be provided. Such faults may cause security violations as they
result in directing traffic to the wrong destinations. This
capability may rely on OAM functions. Equipment must support MPLS
LSP ping [RFC4379]. This may be used to verify end-to-end
connectivity for the LSP (e.g., PW, TE Tunnel, VPN LSP, etc.), and to
verify PE-to-PE connectivity for IPVPN services.
When routing information is advertised from one domain to the other,
operators must be able to guard against situations that result in
traffic hijacking, black-holing, resource stealing (e.g., number of
routes), etc. For instance, in the IPVPN case, an operator must be
able to block routes based on associated route target attributes. In
addition, mechanisms to defend against routing protocol attack must
exist to verify whether a route advertised by a peer for a given VPN
is actually a valid route and whether the VPN has a site attached to
or reachable through that domain.
Equipment (ASBRs and Route Reflectors (RRs)) supporting operation of
BGP must be able to restrict which route target attributes are sent
to and accepted from a BGP peer across an ICI. Equipment (ASBRs,
RRs) should also be able to inform the peer regarding which route
target attributes it will accept from a peer, because sending an
incorrect route target can result in an incorrect cross-connection of
VPNs. Also, sending inappropriate route targets to a peer may
disclose confidential information. This is another example of
defense against routing protocol attacks.
8.1.6. Protection against Spoofed Updates and Route Advertisements
Equipment must support route filtering of routes received via a BGP
peer session by applying policies that include one or more of the
following: AS path, BGP next hop, standard community, or extended
community.
8.1.7. Protection of Confidential Information
The ability to identify and block messages with confidential
information from leaving the trusted domain that can reveal
confidential information about network operation (e.g., performance
OAM messages or LSP ping messages) is required. SPs must have the
flexibility to handle these messages at the ASBR.
Equipment should be able to identify and restrict where it sends
messages that can reveal confidential information about network
operation (e.g., performance OAM messages, LSP Traceroute messages).
Service Providers must have the flexibility to handle these messages
at the ASBR. For example, equipment supporting LSP Traceroute may
limit to which addresses replies can be sent. Note that this
capability should be used with care. For example, if an SP chooses
to prohibit the exchange of LSP ping messages at the ICI, it may make
it more difficult to debug incorrect cross-connection of LSPs or
other problems.
An SP may decide to progress these messages if they arrive from a
trusted provider and are targeted to specific, agreed-on addresses.
Another provider may decide to traffic police, reject, or apply other
policies to these messages. Solutions must enable providers to
control the information that is relayed to another provider about the
path that an LSP takes. For example, when using the RSVP-TE record
route object or LSP ping / trace, a provider must be able to control
the information contained in corresponding messages when sent to
another provider.
8.1.8. Protection against Over-provisioned Number of RSVP-TE
LSPs and Bandwidth Reservation
In addition to the control-plane protection mechanisms listed in the
previous section on control-plane protection with RSVP-TE, the ASBR
must be able both to limit the number of LSPs that can be set up by
other domains and to limit the amount of bandwidth that can be
reserved. A provider's ASBR may deny an LSP setup request or a
bandwidth reservation request sent by another provider's whose limits
have been reached.
8.2. Data-Plane Protection
8.2.1. Protection against DoS in the Data Plane
This is described in Section 5 of this document.
8.2.2. Protection against Label Spoofing
Equipment must be able to verify that a label received across an
interconnect was actually assigned to an LSP arriving across that
interconnect. If a label not assigned to an LSP arrives at this
router from the correct neighboring provider, the packet must be
dropped. This verification can be applied to the top label only.
The top label is the received top label and every label that is
exposed by label popping is to be used for forwarding decisions.
Equipment must provide the capability to drop MPLS-labeled packets if
all labels in the stack are not processed. This lets SPs guarantee
that every label that enters its domain from another carrier is
actually assigned to that carrier.
The following requirements are not directly reflected in this
document but must be used as guidance for addressing further work.
Solutions must NOT force operators to reveal reachability information
to routers within their domains. Note that it is believed that this
requirement is met via other requirements specified in this section
plus the normal operation of IP routing, which does not reveal
individual hosts.
Mechanisms to authenticate and validate a dynamic setup request must
be available. For instance, if dynamic signaling of a TE-LSP or PW
is crossing a domain boundary, there must be a way to detect whether
the LSP source is who it claims to be and that it is allowed to
connect to the destination.
8.2.3. Protection Using Ingress Traffic Policing and Enforcement
The following simple diagram illustrates a potential security issue
on the data plane across an MPLS interconnect:
SP2 - ASBR2 - labeled path - ASBR1 - P1 - SP1's PSN - P2 - PE1
| | | |
|< AS2 >|<MPLS interconnect>|< AS1 >|
Traffic flow direction is from SP2 to SP1
In the case of downstream label assignment, the transit label used by
ASBR2 is allocated by ASBR1, which in turn advertises it to ASBR2
(downstream unsolicited or on-demand); this label is used for a
service context (VPN label, PW VC label, etc.), and this LSP is
normally terminated at a forwarding table belonging to the service
instance on PE (PE1) in SP1.
In the example above, ASBR1 would not know whether the label of an
incoming packet from ASBR2 over the interconnect is a VPN label or
PSN label for AS1. So it is possible (though unlikely) that ASBR2
can be accidentally or intentionally configured such that the
incoming label could match a PSN label (e.g., LDP) in AS1. Then,
this LSP would end up on the global plane of an infrastructure router
(P or PE1), and this could invite a unidirectional attack on that P
or PE1 where the LSP terminates.
To mitigate this threat, implementations should be able to do a
forwarding path look-up for the label on an incoming packet from an
interconnect in a Label Forwarding Information Base (LFIB) space that
is only intended for its own service context or provide a mechanism
on the data plane that would ensure the incoming labels are what
ASBR1 has allocated and advertised.
A similar concept has been proposed in "Requirements for Multi-
Segment Pseudowire Emulation Edge-to-Edge (PWE3)" [RFC5254].
When using upstream label assignment, the upstream source must be
identified and authenticated so the labels can be accepted as from a
trusted source.
9. Summary of MPLS and GMPLS Security
The following summary provides a quick checklist of MPLS and GMPLS
security threats, defense techniques, and the best-practice outlines
for MPLS and GMPLS deployment.
9.1. MPLS and GMPLS Specific Security Threats
9.1.1. Control-Plane Attacks
Types of attacks on the control plane:
- Unauthorized LSP creation
- LSP message interception
Attacks against RSVP-TE: DoS attacks that set up unauthorized LSP
and/or LSP messages.
Attacks against LDP: DoS attack with storms of LDP Hello messages or
LDP TCP SYN messages.
Attacks may be launched from external or internal sources, or through
an SP's management systems.
Attacks may be targeted at the SP's routing protocols or
infrastructure elements.
In general, control protocols may be attacked by:
- MPLS signaling (LDP, RSVP-TE)
- PCE signaling
- IPsec signaling (IKE and IKEv2)
- ICMP and ICMPv6
- L2TP
- BGP-based membership discovery
- Database-based membership discovery (e.g., RADIUS)
- OAM and diagnostic protocols such as LSP ping and LMP
- Other protocols that may be important to the control
infrastructure, e.g., DNS, LMP, NTP, SNMP, and GRE
9.1.2. Data-Plane Attacks
- Unauthorized observation of data traffic
- Data-traffic modification
- Spoofing and replay
- Unauthorized deletion
- Unauthorized traffic-pattern analysis
- Denial of Service
9.2. Defense Techniques
1) Authentication:
- Bidirectional authentication
- Key management
- Management system authentication
- Peer-to-peer authentication
2) Cryptographic techniques
3) Use of IPsec in MPLS/GMPLS networks
4) Encryption for device configuration and management
5) Cryptographic techniques for MPLS pseudowires
6) End-to-End versus Hop-by-Hop protection (CE-CE, PE-PE, PE-CE)
7) Access control techniques
- Filtering
- Firewalls
- Access Control to management interfaces
8) Infrastructure isolation
9) Use of aggregated infrastructure
10) Quality control processes
11) Testable MPLS/GMPLS service
12) End-to-end connectivity verification
13) Hop-by-hop resource configuration verification and discovery
9.3. Service Provider MPLS and GMPLS Best-Practice Outlines
9.3.1. SP Infrastructure Protection
1) General control-plane protection
- Filtering out infrastructure source addresses at edges
- Protocol authentication within the core
- Infrastructure hiding (e.g., disable TTL propagation)
2) RSVP control-plane protection
- RSVP security tools
- Isolation of the trusted domain
- Deactivating RSVP on interfaces with neighbors who are not
authorized to use RSVP
- RSVP neighbor filtering at the protocol level and data-plane
level
- Authentication for RSVP messages
- RSVP message pacing
3) LDP control-plane protection (similar techniques as for RSVP)
4) Data-plane protection
- User access link protection
- Link authentication
- Access routing control (e.g., prefix limits, route dampening,
routing table limits (such as VRF limits)
- Access QoS control
- Customer service monitoring tools
- Use of LSP ping (with its own control-plane security) to verify
end-to-end connectivity of MPLS LSPs
- LMP (with its own security) to verify hop-by-hop connectivity.
9.3.2. Inter-Provider Security
Inter-provider connections are high security risk areas. Similar
techniques and procedures as described for SP's general core
protection are listed below for inter-provider connections.
1) Control-plane protection at inter-provider connections
- Authentication of signaling sessions
- Protection against DoS attacks in the control plane
- Protection against malformed packets
- Ability to enable/disable specific protocols
- Protection against incorrect cross connection
- Protection against spoofed updates and route advertisements
- Protection of confidential information
- Protection against an over-provisioned number of RSVP-TE LSPs
and bandwidth reservation
2) Data-plane protection at the inter-provider connections
- Protection against DoS in the data plane
- Protection against label spoofing
For MPLS VPN interconnections [RFC4364], in practice, inter-AS option
a), VRF-to-VRF connections at the AS (Autonomous System) border, is
commonly used for inter-provider connections. Option c), Multi-hop
EBGP redistribution of labeled VPN-IPv4 routes between source and
destination ASes with EBGP redistribution of labeled IPv4 routes from
AS to a neighboring AS, on the other hand, is not normally used for
inter-provider connections due to higher security risks. For more
details, please see [RFC4111].
10. Security Considerations
Security considerations constitute the sole subject of this memo and
hence are discussed throughout. Here we recap what has been
presented and explain at a high level the role of each type of
consideration in an overall secure MPLS/GMPLS system.
The document describes a number of potential security threats. Some
of these threats have already been observed occurring in running
networks; others are largely hypothetical at this time.
DoS attacks and intrusion attacks from the Internet against an SPs'
infrastructure have been seen. DoS "attacks" (typically not
malicious) have also been seen in which CE equipment overwhelms PE
equipment with high quantities or rates of packet traffic or routing
information. Operational or provisioning errors are cited by SPs as
one of their prime concerns.
The document describes a variety of defensive techniques that may be
used to counter the suspected threats. All of the techniques
presented involve mature and widely implemented technologies that are
practical to implement.
The document describes the importance of detecting, monitoring, and
reporting attacks, both successful and unsuccessful. These
activities are essential for "understanding one's enemy", mobilizing
new defenses, and obtaining metrics about how secure the MPLS/GMPLS
network is. As such, they are vital components of any complete PPVPN
security system.
The document evaluates MPLS/GMPLS security requirements from a
customer's perspective as well as from a service provider's
perspective. These sections re-evaluate the identified threats from
the perspectives of the various stakeholders and are meant to assist
equipment vendors and service providers, who must ultimately decide
what threats to protect against in any given configuration or service
offering.
11. References
11.1. Normative References
[RFC2747] Baker, F., Lindell, B., and M. Talwar, "RSVP
Cryptographic Authentication", RFC 2747, January
2000.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon,
"Multiprotocol Label Switching Architecture", RFC
3031, January 2001.
[RFC3097] Braden, R. and L. Zhang, "RSVP Cryptographic
Authentication -- Updated Message Type Value", RFC
3097, April 2001.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T.,
Srinivasan, V., and G. Swallow, "RSVP-TE:
Extensions to RSVP for LSP Tunnels", RFC 3209,
December 2001.
[RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945, October
2004.
[RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter
Mode (GCM) in IPsec Encapsulating Security Payload
(ESP)", RFC 4106, June 2005.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
December 2005.
[RFC4306] Kaufman, C., Ed., "Internet Key Exchange (IKEv2)
Protocol", RFC 4306, December 2005.
[RFC4309] Housley, R., "Using Advanced Encryption Standard
(AES) CCM Mode with IPsec Encapsulating Security
Payload (ESP)", RFC 4309, December 2005.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual
Private Networks (VPNs)", RFC 4364, February 2006.
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-
Protocol Label Switched (MPLS) Data Plane
Failures", RFC 4379, February 2006.
[RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith,
T., and G. Heron, "Pseudowire Setup and Maintenance
Using the Label Distribution Protocol (LDP)", RFC
4447, April 2006.
[RFC4835] Manral, V., "Cryptographic Algorithm Implementation
Requirements for Encapsulating Security Payload
(ESP) and Authentication Header (AH)", RFC 4835,
April 2007.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer
Security (TLS) Protocol Version 1.2", RFC 5246,
August 2008.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas,
Ed., "LDP Specification", RFC 5036, October 2007.
[STD62] Harrington, D., Presuhn, R., and B. Wijnen, "An
Architecture for Describing Simple Network
Management Protocol (SNMP) Management Frameworks",
STD 62, RFC 3411, December 2002.
Case, J., Harrington, D., Presuhn, R., and B.
Wijnen, "Message Processing and Dispatching for the
Simple Network Management Protocol (SNMP)", STD 62,
RFC 3412, December 2002.
Levi, D., Meyer, P., and B. Stewart, "Simple
Network Management Protocol (SNMP) Applications",
STD 62, RFC 3413, December 2002.
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.
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.
Presuhn, R., Ed., "Version 2 of the Protocol
Operations for the Simple Network Management
Protocol (SNMP)", STD 62, RFC 3416, December 2002.
Presuhn, R., Ed., "Transport Mappings for the
Simple Network Management Protocol (SNMP)", STD 62,
RFC 3417, December 2002.
Presuhn, R., Ed., "Management Information Base
(MIB) for the Simple Network Management Protocol
(SNMP)", STD 62, RFC 3418, December 2002.
[STD8] Postel, J. and J. Reynolds, "Telnet Protocol
Specification", STD 8, RFC 854, May 1983.
Postel, J. and J. Reynolds, "Telnet Option
Specifications", STD 8, RFC 855, May 1983.
11.2. Informative References
[OIF-SMI-01.0] Renee Esposito, "Security for Management Interfaces
to Network Elements", Optical Internetworking
Forum, Sept. 2003.
[OIF-SMI-02.1] Renee Esposito, "Addendum to the Security for
Management Interfaces to Network Elements", Optical
Internetworking Forum, March 2006.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC:
Keyed-Hashing for Message Authentication", RFC
2104, February 1997.
[RFC2411] Thayer, R., Doraswamy, N., and R. Glenn, "IP
Security Document Roadmap", RFC 2411, November
1998.
[RFC3174] Eastlake 3rd, D. and P. Jones, "US Secure Hash
Algorithm 1 (SHA1)", RFC 3174, September 2001.
[RFC3562] Leech, M., "Key Management Considerations for the
TCP MD5 Signature Option", RFC 3562, July 2003.
[RFC3631] Bellovin, S., Ed., Schiller, J., Ed., and C.
Kaufman, Ed., "Security Mechanisms for the
Internet", RFC 3631, December 2003.
[RFC3704] Baker, F. and P. Savola, "Ingress Filtering for
Multihomed Networks", BCP 84, RFC 3704, March 2004.
[RFC3985] Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire
Emulation Edge-to-Edge (PWE3) Architecture", RFC
3985, March 2005.
[RFC4107] Bellovin, S. and R. Housley, "Guidelines for
Cryptographic Key Management", BCP 107, RFC 4107,
June 2005.
[RFC4110] Callon, R. and M. Suzuki, "A Framework for Layer 3
Provider-Provisioned Virtual Private Networks
(PPVPNs)", RFC 4110, July 2005.
[RFC4111] Fang, L., Ed., "Security Framework for Provider-
Provisioned Virtual Private Networks (PPVPNs)", RFC
4111, July 2005.
[RFC4230] Tschofenig, H. and R. Graveman, "RSVP Security
Properties", RFC 4230, December 2005.
[RFC4308] Hoffman, P., "Cryptographic Suites for IPsec", RFC
4308, December 2005.
[RFC4377] Nadeau, T., Morrow, M., Swallow, G., Allan, D., and
S. Matsushima, "Operations and Management (OAM)
Requirements for Multi-Protocol Label Switched
(MPLS) Networks", RFC 4377, February 2006.
[RFC4378] Allan, D., Ed., and T. Nadeau, Ed., "A Framework
for Multi-Protocol Label Switching (MPLS)
Operations and Management (OAM)", RFC 4378,
February 2006.
[RFC4593] Barbir, A., Murphy, S., and Y. Yang, "Generic
Threats to Routing Protocols", RFC 4593, October
2006.
[RFC4778] Kaeo, M., "Operational Security Current Practices
in Internet Service Provider Environments", RFC
4778, January 2007.
[RFC4808] Bellovin, S., "Key Change Strategies for TCP-MD5",
RFC 4808, March 2007.
[RFC4864] Van de Velde, G., Hain, T., Droms, R., Carpenter,
B., and E. Klein, "Local Network Protection for
IPv6", RFC 4864, May 2007.
[RFC4869] Law, L. and J. Solinas, "Suite B Cryptographic
Suites for IPsec", RFC 4869, May 2007.
[RFC5254] Bitar, N., Ed., Bocci, M., Ed., and L. Martini,
Ed., "Requirements for Multi-Segment Pseudowire
Emulation Edge-to-Edge (PWE3)", RFC 5254, October
2008.
[MFA-MPLS-ICI] N. Bitar, "MPLS InterCarrier Interconnect Technical
Specification," IP/MPLS Forum 19.0.0, April 2008.
[OIF-Sec-Mag] R. Esposito, R. Graveman, and B. Hazzard, "Security
for Management Interfaces to Network Elements,"
OIF-SMI-01.0, September 2003.
[BACKBONE-ATTKS] Savola, P., "Backbone Infrastructure Attacks and
Protections", Work in Progress, January 2007.
[OPSEC-FILTER] Morrow, C., Jones, G., and V. Manral, "Filtering
and Rate Limiting Capabilities for IP Network
Infrastructure", Work in Progress, July 2007.
[IPSECME-ROADMAP] Frankel, S. and S. Krishnan, "IP Security (IPsec)
and Internet Key Exchange (IKE) Document Roadmap",
Work in Progress, May 2010.
[OPSEC-EFFORTS] Lonvick, C. and D. Spak, "Security Best Practices
Efforts and Documents", Work in Progress, May 2010.
[RSVP-key] Behringer, M. and F. Le Faucheur, "Applicability of
Keying Methods for RSVP Security", Work in
Progress, June 2009.
12. Acknowledgements
The authors and contributors would also like to acknowledge the
helpful comments and suggestions from Sam Hartman, Dimitri
Papadimitriou, Kannan Varadhan, Stephen Farrell, Mircea Pisica, Scott
Brim in particular for his comments and discussion through GEN-ART
review,as well as Suresh Krishnan for his GEN-ART review and
comments. The authors would like to thank Sandra Murphy and Tim Polk
for their comments and help through Security AD review, thank Pekka
Savola for his comments through ops-dir review, and Amanda Baber for
her IANA review.
This document has used relevant content from RFC 4111 "Security
Framework of Provider Provisioned VPN for Provider-Provisioned
Virtual Private Networks (PPVPNs)" [RFC4111]. We acknowledge the
authors of RFC 4111 for the valuable information and text.
Authors:
Luyuan Fang, Ed., Cisco Systems, Inc.
Michael Behringer, Cisco Systems, Inc.
Ross Callon, Juniper Networks
Richard Graveman, RFG Security, LLC
J. L. Le Roux, France Telecom
Raymond Zhang, British Telecom
Paul Knight, Individual Contributor
Yaakov Stein, RAD Data Communications
Nabil Bitar, Verizon
Monique Morrow, Cisco Systems, Inc.
Adrian Farrel, Old Dog Consulting
As a design team member for the MPLS Security Framework, Jerry Ash
also made significant contributions to this document.
13. Contributors' Contact Information
Michael Behringer
Cisco Systems, Inc.
Village d'Entreprises Green Side
400, Avenue Roumanille, Batiment T 3
06410 Biot, Sophia Antipolis
FRANCE
EMail: mbehring@cisco.com
Ross Callon
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
USA
EMail: rcallon@juniper.net
Richard Graveman
RFG Security
15 Park Avenue
Morristown, NJ 07960
EMail: rfg@acm.org
Jean-Louis Le Roux
France Telecom
2, avenue Pierre-Marzin
22307 Lannion Cedex
FRANCE
EMail: jeanlouis.leroux@francetelecom.com
Raymond Zhang
British Telecom
BT Center
81 Newgate Street
London, EC1A 7AJ
United Kingdom
EMail: raymond.zhang@bt.com
Paul Knight
39 N. Hancock St.
Lexington, MA 02420
EMail: paul.the.knight@gmail.com
Yaakov (Jonathan) Stein
RAD Data Communications
24 Raoul Wallenberg St., Bldg C
Tel Aviv 69719
ISRAEL
EMail: yaakov_s@rad.com
Nabil Bitar
Verizon
40 Sylvan Road
Waltham, MA 02145
EMail: nabil.bitar@verizon.com
Monique Morrow
Glatt-com
CH-8301 Glattzentrum
Switzerland
EMail: mmorrow@cisco.com
Adrian Farrel
Old Dog Consulting
EMail: adrian@olddog.co.uk
Editor's Address
Luyuan Fang (editor)
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough, MA 01719
USA
EMail: lufang@cisco.com