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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


 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

Fang Informational [Page 1] RFC 5920 MPLS/GMPLS Security Framework July 2010

Copyright Notice

 Copyright (c) 2010 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 ( in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.
 This document may contain material from IETF Documents or IETF
 Contributions published or made publicly available before November
 10, 2008.  The person(s) controlling the copyright in some of this
 material may not have granted the IETF Trust the right to allow
 modifications of such material outside the IETF Standards Process.
 Without obtaining an adequate license from the person(s) controlling
 the copyright in such materials, this document may not be modified
 outside the IETF Standards Process, and derivative works of it may
 not be created outside the IETF Standards Process, except to format
 it for publication as an RFC or to translate it into languages other
 than English.

Fang Informational [Page 2] RFC 5920 MPLS/GMPLS Security Framework July 2010

Table of Contents

 1. Introduction ....................................................4
 2. Terminology .....................................................5
    2.1. Acronyms and Abbreviations .................................5
    2.2. MPLS and GMPLS Terminology .................................6
 3. Security Reference Models .......................................8
 4. Security Threats ...............................................10
    4.1. Attacks on the Control Plane ..............................12
    4.2. Attacks on the Data Plane .................................15
    4.3. Attacks on Operation and Management Plane .................17
    4.4. Insider Attacks Considerations ............................19
 5. Defensive Techniques for MPLS/GMPLS Networks ...................19
    5.1. Authentication ............................................20
    5.2. Cryptographic Techniques ..................................22
    5.3. Access Control Techniques .................................33
    5.4. Use of Isolated Infrastructure ............................38
    5.5. Use of Aggregated Infrastructure ..........................38
    5.6. Service Provider Quality Control Processes ................39
    5.7. Deployment of Testable MPLS/GMPLS Service .................39
    5.8. Verification of Connectivity ..............................40
 6. Monitoring, Detection, and Reporting of Security Attacks .......40
 7. Service Provider General Security Requirements .................42
    7.1. Protection within the Core Network ........................42
    7.2. Protection on the User Access Link ........................46
    7.3. General User Requirements for MPLS/GMPLS Providers ........48
 8. Inter-Provider Security Requirements ...........................48
    8.1. Control-Plane Protection ..................................49
    8.2. Data-Plane Protection .....................................53
 9. Summary of MPLS and GMPLS Security .............................54
    9.1. MPLS and GMPLS Specific Security Threats ..................55
    9.2. Defense Techniques ........................................56
    9.3. Service Provider MPLS and GMPLS Best-Practice Outlines ....57
 10. Security Considerations .......................................59
 11. References ....................................................59
    11.1. Normative References .....................................59
    11.2. Informative References ...................................62
 12. Acknowledgements ..............................................64
 13. Contributors' Contact Information .............................65

Fang Informational [Page 3] RFC 5920 MPLS/GMPLS Security Framework July 2010

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

Fang Informational [Page 4] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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

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

Fang Informational [Page 5] RFC 5920 MPLS/GMPLS Security Framework July 2010

 PW        Pseudowire
 QoS       Quality of Service
 RR        Route Reflector
 RSVP      Resource Reservation Protocol
 RSVP-TE   Resource Reservation Protocol with Traffic Engineering
 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.

Fang Informational [Page 6] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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
 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.

Fang Informational [Page 7] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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
 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
 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.

Fang Informational [Page 8] RFC 5920 MPLS/GMPLS Security Framework July 2010

    +------------+    /               \         +------------+
    | 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

Fang Informational [Page 9] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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 |
              |               |        |                |
              +---------------+        +----------------+
                              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
 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
  1. Observation, modification, or deletion of a provider's or user's


  1. Replay of a provider's or user's data.
  1. Injection of inauthentic data into a provider's or user's traffic


  1. Traffic pattern analysis on a provider's or user's traffic.
  1. Disruption of a provider's or user's connectivity.

Fang Informational [Page 10] RFC 5920 MPLS/GMPLS Security Framework July 2010

  1. Degradation of a provider's service quality.
  1. 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:
  1. Other users whose services are provided by the same MPLS/GMPLS


  1. The MPLS/GMPLS SP or persons working for it.
  1. Other persons who obtain physical access to an MPLS/GMPLS SP's


  1. Other persons who use social engineering methods to influence the

behavior of an SP's personnel.

  1. Users of the MPLS/GMPLS network itself, e.g., intra-VPN threats.

(Such threats are beyond the scope of this document.)

  1. Others, e.g., attackers from the Internet at large.
  1. 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.

  1. 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:
  1. An MPLS/GMPLS core interconnecting with another provider's core.
  1. 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

Fang Informational [Page 11] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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.

Fang Informational [Page 12] RFC 5920 MPLS/GMPLS Security Framework July 2010

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.)

Fang Informational [Page 13] RFC 5920 MPLS/GMPLS Security Framework July 2010

 The attacks described in the following sections may each have denial
 of service as one of their effects.  Other DoS attacks are also

4.1.6. Attacks on the SP's MPLS/GMPLS Equipment via Management

 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
  1. A site being connected into the "wrong" VPN.
  1. Traffic being replicated and sent to an unauthorized user.
  1. Two or more VPNs being improperly merged together.
  1. A point-to-point VPN connecting the wrong two points.
  1. 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].

Fang Informational [Page 14] RFC 5920 MPLS/GMPLS Security Framework July 2010

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:
  1. MPLS signaling (LDP, RSVP-TE) discussed above in subsections 4.1.4

and 4.1.3

  1. PCE signaling
  1. IPsec signaling (IKE and IKEv2)
  1. ICMP and ICMPv6
  1. L2TP
  1. BGP-based membership discovery
  1. Database-based membership discovery (e.g., RADIUS)
  1. 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.

Fang Informational [Page 15] RFC 5920 MPLS/GMPLS Security Framework July 2010

4.2.2. Modification of Data Traffic

 This refers to modifying the contents of packets as they traverse the

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

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

Fang Informational [Page 16] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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
 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

Fang Informational [Page 17] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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

Fang Informational [Page 18] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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,

Fang Informational [Page 19] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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
 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

Fang Informational [Page 20] RFC 5920 MPLS/GMPLS Security Framework July 2010

 techniques may, however, be useful against resource exhaustion
 attacks based on the exhaustion of state information (e.g., TCP SYN
 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
 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
 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

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

Fang Informational [Page 21] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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

Fang Informational [Page 22] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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:
  1. 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.

  1. 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.
  1. 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.
  1. 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

Fang Informational [Page 23] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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,

Fang Informational [Page 24] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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.

Fang Informational [Page 25] RFC 5920 MPLS/GMPLS Security Framework July 2010

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.
  1. Secure Shell (SSH) offers protection for TELNET [STD8] or

terminal-like connections to allow device configuration.

  1. SNMPv3 [STD62] provides encrypted and authenticated protection for

SNMP-managed devices.

  1. 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.
  1. 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.
  1. 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.
  1. 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].

Fang Informational [Page 26] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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:
  1. Unauthorized setup of a PW (e.g., to gain access to a customer


  1. Unauthorized teardown of a PW (thus causing denial of service)
  1. Malicious reroute of a PW
  1. Unauthorized observation of PW packets
  1. Traffic analysis of PW connectivity
  1. Unauthorized insertion of PW packets
  1. Unauthorized modification of PW packets
  1. Unauthorized deletion of PW packets replay of PW packets
  1. 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
  1. Since the PW label is the only identifier in the packet, there is

no authenticatable source address.

  1. Since guessing a valid PW label is not difficult, it is relatively

easy to introduce seemingly valid foreign packets.

  1. Since the PW packet is not self-describing, minor modification of

control-plane packets renders the data-plane traffic useless.

Fang Informational [Page 27] RFC 5920 MPLS/GMPLS Security Framework July 2010

  1. The control-word sequence number processing algorithm is

susceptible to a DoS attack.

 The PWE control protocol introduces its own weaknesses:
  1. No (secure) peer autodiscovery technique has been standardized .
  1. 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
  1. Alternately, desired PWs may be torn down, giving rise to denial

of service.

 The following characteristics of PWs can be considered security
  1. The most obvious attacks require compromising edge or core routers

(although not necessarily those along the PW path).

  1. Adequate protection of the control-plane messaging is sufficient

to rule out many types of attacks.

  1. 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

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-

Fang Informational [Page 28] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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).
 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:
  1. 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?
  1. Vulnerability to device compromise - assuming an attacker can get

access to a device (or freely alter its configuration), would the

    data be protected?
  1. 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?

Fang Informational [Page 29] RFC 5920 MPLS/GMPLS Security Framework July 2010

  1. 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.
  1. 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
       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
 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

Fang Informational [Page 30] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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.

Fang Informational [Page 31] RFC 5920 MPLS/GMPLS Security Framework July 2010

 Given the tradeoffs discussed above, a few conclusions can be drawn:
  1. 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).
  1. If protection from link eavesdropping or tampering is all that is

important, then configurations 1 and 4 are equivalent.

  1. 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.
  1. 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.
  1. 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.
  1. If the availability of enhanced services support from the SP is

most important, then 4 is best.

  1. 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.

Fang Informational [Page 32] RFC 5920 MPLS/GMPLS Security Framework July 2010

 In addition to the simplified models, the following should also be
  1. There are reasons, perhaps, to protect a specific P-to-P or PE-


  1. 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.)
  1. It may be appropriate that, for example, cryptographic integrity

checks are applied end to end, and confidentiality is applied over

    a shorter span.
  1. Different cryptographic protection may be required for control

protocols and data traffic.

  1. 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:
  1. 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.

Fang Informational [Page 33] RFC 5920 MPLS/GMPLS Security Framework July 2010

  1. 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
 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.

Fang Informational [Page 34] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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:
  1. 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.
  1. Set CoS
       A filter may be used to set the class of service associated
       with the packet.
  1. Count packets or bytes
  1. 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).

Fang Informational [Page 35] RFC 5920 MPLS/GMPLS Security Framework July 2010

  1. 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

Fang Informational [Page 36] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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 (

Fang Informational [Page 37] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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,

Fang Informational [Page 38] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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

Fang Informational [Page 39] RFC 5920 MPLS/GMPLS Security Framework July 2010

 much ensures that there is no unintended connectivity to some other

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).

Fang Informational [Page 40] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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:
  1. Source address allows the understanding of who is originating the


  1. Destination address tells who is receiving the traffic.
  1. Ports characterize the application utilizing the traffic.
  1. Class of service examines the priority of the traffic.

Fang Informational [Page 41] RFC 5920 MPLS/GMPLS Security Framework July 2010

  1. The device interface tells how traffic is being utilized by the

network device.

  1. Tallied packets and bytes show the amount of traffic.
  1. Flow timestamps allow the understanding of the life of a flow;

timestamps are useful for calculating packets and bytes per

  1. Next-hop IP addresses including BGP routing Autonomous Systems


  1. Subnet mask for the source and destination addresses are for

calculating prefixes.

  1. 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

  1. 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

Fang Informational [Page 42] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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.
  1. 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.
  1. 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
 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

Fang Informational [Page 43] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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

  1. 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
 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.

Fang Informational [Page 44] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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.
  1. 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.
  1. 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

Fang Informational [Page 45] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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.

Fang Informational [Page 46] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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:
  1. 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
  1. Applying route dampening at the PE on received routing updates
  1. 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.

Fang Informational [Page 47] RFC 5920 MPLS/GMPLS Security Framework July 2010

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:
  1. User control plane separation through routing isolation when

applicable, for example, in the case of MPLS VPNs.

  1. Protection against intrusion, DoS attacks, and spoofing
  1. Access Authentication
  1. Techniques highlighted throughout this document that identify

methodologies for the protection of resources and the MPLS/GMPLS

 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

Fang Informational [Page 48] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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

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

Fang Informational [Page 49] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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

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

Fang Informational [Page 50] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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

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

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.

Fang Informational [Page 51] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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

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.

Fang Informational [Page 52] RFC 5920 MPLS/GMPLS Security Framework July 2010

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.

Fang Informational [Page 53] RFC 5920 MPLS/GMPLS Security Framework July 2010

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.

Fang Informational [Page 54] RFC 5920 MPLS/GMPLS Security Framework July 2010

9.1. MPLS and GMPLS Specific Security Threats

9.1.1. Control-Plane Attacks

 Types of attacks on the control plane:
  1. Unauthorized LSP creation
  1. 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:
  1. MPLS signaling (LDP, RSVP-TE)
  1. PCE signaling
  1. IPsec signaling (IKE and IKEv2)
  1. ICMP and ICMPv6
  1. L2TP
  1. BGP-based membership discovery
  1. Database-based membership discovery (e.g., RADIUS)
  1. OAM and diagnostic protocols such as LSP ping and LMP
  1. Other protocols that may be important to the control

infrastructure, e.g., DNS, LMP, NTP, SNMP, and GRE

Fang Informational [Page 55] RFC 5920 MPLS/GMPLS Security Framework July 2010

9.1.2. Data-Plane Attacks

  1. Unauthorized observation of data traffic
  1. Data-traffic modification
  1. Spoofing and replay
  1. Unauthorized deletion
  1. Unauthorized traffic-pattern analysis
  1. Denial of Service

9.2. Defense Techniques

 1)  Authentication:
  1. Bidirectional authentication
  1. Key management
  1. Management system authentication
  1. 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
  1. Filtering
  1. Firewalls
  1. Access Control to management interfaces
 8)  Infrastructure isolation
 9)  Use of aggregated infrastructure

Fang Informational [Page 56] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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
  1. Filtering out infrastructure source addresses at edges
  1. Protocol authentication within the core
  1. Infrastructure hiding (e.g., disable TTL propagation)
 2) RSVP control-plane protection
  1. RSVP security tools
  1. Isolation of the trusted domain
  1. Deactivating RSVP on interfaces with neighbors who are not

authorized to use RSVP

  1. RSVP neighbor filtering at the protocol level and data-plane


  1. Authentication for RSVP messages
  1. RSVP message pacing
 3) LDP control-plane protection (similar techniques as for RSVP)
 4) Data-plane protection
  1. User access link protection
  1. Link authentication
  1. Access routing control (e.g., prefix limits, route dampening,

routing table limits (such as VRF limits)

  1. Access QoS control

Fang Informational [Page 57] RFC 5920 MPLS/GMPLS Security Framework July 2010

  1. Customer service monitoring tools
  1. Use of LSP ping (with its own control-plane security) to verify

end-to-end connectivity of MPLS LSPs

  1. 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
  1. Authentication of signaling sessions
  1. Protection against DoS attacks in the control plane
  1. Protection against malformed packets
  1. Ability to enable/disable specific protocols
  1. Protection against incorrect cross connection
  1. Protection against spoofed updates and route advertisements
  1. Protection of confidential information
  1. Protection against an over-provisioned number of RSVP-TE LSPs

and bandwidth reservation

 2) Data-plane protection at the inter-provider connections
  1. Protection against DoS in the data plane
  1. 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].

Fang Informational [Page 58] RFC 5920 MPLS/GMPLS Security Framework July 2010

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

11. References

11.1. Normative References

 [RFC2747]         Baker, F., Lindell, B., and M. Talwar, "RSVP
                   Cryptographic Authentication", RFC 2747, January

Fang Informational [Page 59] RFC 5920 MPLS/GMPLS Security Framework July 2010

 [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
 [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.

Fang Informational [Page 60] RFC 5920 MPLS/GMPLS Security Framework July 2010

 [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.

Fang Informational [Page 61] RFC 5920 MPLS/GMPLS Security Framework July 2010

 [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
 [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.

Fang Informational [Page 62] RFC 5920 MPLS/GMPLS Security Framework July 2010

 [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
 [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
 [MFA-MPLS-ICI]    N. Bitar, "MPLS InterCarrier Interconnect Technical
                   Specification," IP/MPLS Forum 19.0.0, April 2008.

Fang Informational [Page 63] RFC 5920 MPLS/GMPLS Security Framework July 2010

 [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.
 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

Fang Informational [Page 64] RFC 5920 MPLS/GMPLS Security Framework July 2010

 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
 Ross Callon
 Juniper Networks
 10 Technology Park Drive
 Westford, MA 01886
 Richard Graveman
 RFG Security
 15 Park Avenue
 Morristown, NJ  07960
 Jean-Louis Le Roux
 France Telecom
 2, avenue Pierre-Marzin
 22307 Lannion Cedex
 Raymond Zhang
 British Telecom
 BT Center
 81 Newgate Street
 London, EC1A 7AJ
 United Kingdom

Fang Informational [Page 65] RFC 5920 MPLS/GMPLS Security Framework July 2010

 Paul Knight
 39 N. Hancock St.
 Lexington, MA 02420
 Yaakov (Jonathan) Stein
 RAD Data Communications
 24 Raoul Wallenberg St., Bldg C
 Tel Aviv  69719
 Nabil Bitar
 40 Sylvan Road
 Waltham, MA 02145
 Monique Morrow
 CH-8301 Glattzentrum
 Adrian Farrel
 Old Dog Consulting

Editor's Address

 Luyuan Fang (editor)
 Cisco Systems, Inc.
 300 Beaver Brook Road
 Boxborough, MA 01719

Fang Informational [Page 66]

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