path: root/doc/rfc/rfc5920.txt

Internet Engineering Task Force (IETF)                      L. Fang, Ed.
Request for Comments: 5920                           Cisco Systems, Inc.
Category: Informational                                        July 2010
ISSN: 2070-1721


             Security Framework for MPLS and GMPLS Networks

Abstract

   This document provides a security framework for Multiprotocol Label
   Switching (MPLS) and Generalized Multiprotocol Label Switching
   (GMPLS) Networks.  This document addresses the security aspects that
   are relevant in the context of MPLS and GMPLS.  It describes the
   security threats, the related defensive techniques, and the
   mechanisms for detection and reporting.  This document emphasizes
   RSVP-TE and LDP security considerations, as well as inter-AS and
   inter-provider security considerations for building and maintaining
   MPLS and GMPLS networks across different domains or different
   Service Providers.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any
   errata, and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc5920.















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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
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   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
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   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.

























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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












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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



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   Documents" [OPSEC-EFFORTS] and "Security Mechanisms for the Internet"
   [RFC3631] for general network operation security considerations.  It
   is not our intention, however, to formulate precise "requirements"
   for each specific technology in terms of defining the mechanisms and
   techniques that must be implemented to satisfy such security
   requirements.

2.  Terminology

2.1.  Acronyms and Abbreviations

   AS        Autonomous System
   ASBR      Autonomous System Border Router
   ATM       Asynchronous Transfer Mode
   BGP       Border Gateway Protocol
   BFD       Bidirectional Forwarding Detection
   CE        Customer-Edge device
   CoS       Class of Service
   CPU       Central Processing Unit
   DNS       Domain Name System
   DoS       Denial of Service
   ESP       Encapsulating Security Payload
   FEC       Forwarding Equivalence Class
   GMPLS     Generalized Multi-Protocol Label Switching
   GCM       Galois Counter Mode
   GRE       Generic Routing Encapsulation
   ICI       InterCarrier Interconnect
   ICMP      Internet Control Message Protocol
   ICMPv6    ICMP in IP Version 6
   IGP       Interior Gateway Protocol
   IKE       Internet Key Exchange
   IP        Internet Protocol
   IPsec     IP Security
   IPVPN     IP-based VPN
   LDP       Label Distribution Protocol
   L2TP      Layer 2 Tunneling Protocol
   LMP       Link Management Protocol
   LSP       Label Switched Path
   LSR       Label Switching Router
   MD5       Message Digest Algorithm
   MPLS      Multiprotocol Label Switching
   MP-BGP    Multiprotocol BGP
   NTP       Network Time Protocol
   OAM       Operations, Administration, and Maintenance
   PCE       Path Computation Element
   PE        Provider-Edge device
   PPVPN     Provider-Provisioned Virtual Private Network
   PSN       Packet-Switched Network



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   PW        Pseudowire
   QoS       Quality of Service
   RR        Route Reflector
   RSVP      Resource Reservation Protocol
   RSVP-TE   Resource Reservation Protocol with Traffic Engineering
                  Extensions
   SLA       Service Level Agreement
   SNMP      Simple Network Management Protocol
   SP        Service Provider
   SSH       Secure Shell
   SSL       Secure Sockets Layer
   SYN       Synchronize packet in TCP
   TCP       Transmission Control Protocol
   TDM       Time Division Multiplexing
   TE        Traffic Engineering
   TLS       Transport Layer Security
   ToS       Type of Service
   TTL       Time-To-Live
   UDP       User Datagram Protocol
   VC        Virtual Circuit
   VPN       Virtual Private Network
   WG        Working Group of IETF
   WSS       Web Services Security

2.2.  MPLS and GMPLS Terminology

   This document uses MPLS- and GMPLS-specific terminology.  Definitions
   and details about MPLS and GMPLS terminology can be found in
   [RFC3031] and [RFC3945].  The most important definitions are repeated
   in this section; for other definitions, the reader is referred to
   [RFC3031] and [RFC3945].

   Core network: An MPLS/GMPLS core network is defined as the central
   network infrastructure that consists of P and PE routers.  An
   MPLS/GMPLS core network may consist of one or more networks belonging
   to a single SP.

   Customer Edge (CE) device: A Customer Edge device is a router or a
   switch in the customer's network interfacing with the Service
   Provider's network.

   Forwarding Equivalence Class (FEC): A group of IP packets that are
   forwarded in the same manner (e.g., over the same path, with the same
   forwarding treatment).

   Label: A short, fixed length, physically contiguous identifier,
   usually of local significance.




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   Label merging: the replacement of multiple incoming labels for a
   particular FEC with a single outgoing label.

   Label Switched Hop: A hop between two MPLS nodes, on which forwarding
   is done using labels.

   Label Switched Path (LSP): The path through one or more LSRs at one
   level of the hierarchy followed by packets in a particular FEC.

   Label Switching Routers (LSRs): An MPLS/GMPLS node assumed to have a
   forwarding plane that is capable of (a) recognizing either packet or
   cell boundaries, and (b) being able to process either packet headers
   or cell headers.

   Loop Detection: A method of dealing with loops in which loops are
   allowed to be set up, and data may be transmitted over the loop, but
   the loop is later detected.

   Loop Prevention: A method of dealing with loops in which data is
   never transmitted over a loop.

   Label Stack: An ordered set of labels.

   Merge Point: A node at which label merging is done.

   MPLS Domain: A contiguous set of nodes that perform MPLS routing and
   forwarding and are also in one Routing or Administrative Domain.

   MPLS Edge Node: An MPLS node that connects an MPLS domain with a node
   outside of the domain, either because it does not run MPLS, or
   because it is in a different domain.  Note that if an LSR has a
   neighboring host not running MPLS, then that LSR is an MPLS edge
   node.

   MPLS Egress Node: An MPLS edge node in its role in handling traffic
   as it leaves an MPLS domain.

   MPLS Ingress Node: A MPLS edge node in its role in handling traffic
   as it enters a MPLS domain.

   MPLS Label: A label carried in a packet header, which represents the
   packet's FEC.

   MPLS Node: A node running MPLS.  An MPLS node is aware of MPLS
   control protocols, runs one or more routing protocols, and is capable
   of forwarding packets based on labels.  An MPLS node may optionally
   be also capable of forwarding native IP packets.




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   Multiprotocol Label Switching (MPLS): MPLS is an architecture for
   efficient data packet switching and routing.  MPLS assigns data
   packets with labels.  Instead of performing the longest match for
   each packet's destination as in conventional IP forwarding, MPLS
   makes the packet-forwarding decisions solely on the contents of the
   label without examining the packet itself.  This allows the creation
   of end-to-end circuits across any type of transport medium, using any
   protocols.

   P: Provider Router.  A Provider Router is a router in the Service
   Provider's core network that does not have interfaces directly
   towards the customer.  A P router is used to interconnect the PE
   routers and/or other P routers within the core network.

   PE: Provider Edge device.  A Provider Edge device is the equipment in
   the Service Provider's network that interfaces with the equipment in
   the customer's network.

   PPVPN: Provider-Provisioned Virtual Private Network, including Layer
   2 VPNs and Layer 3 VPNs.

   VPN: Virtual Private Network, which restricts communication between a
   set of sites, making use of an IP backbone shared by traffic not
   going to or not coming from those sites [RFC4110].

3.  Security Reference Models

   This section defines a reference model for security in MPLS/GMPLS
   networks.

   This document defines each MPLS/GMPLS core in a single domain to be a
   trusted zone.  A primary concern is about security aspects that
   relate to breaches of security from the "outside" of a trusted zone
   to the "inside" of this zone.  Figure 1 depicts the concept of
   trusted zones within the MPLS/GMPLS framework.
















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




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   inter-AS LSPs, the other provider is considered an untrusted but
   authorized neighbor.

                +---------------+        +----------------+
                |               |        |                |
                | MPLS/GMPLS   ASBR1----ASBR3  MPLS/GMPLS |
          CE1--PE1   Network    |        |     Network   PE2--CE2
                | Provider A   ASBR2----ASBR4  Provider B |
                |               |        |                |
                +---------------+        +----------------+
                                InterCarrier
                                Interconnect (ICI)
   For Provider A:
        Trusted Zone: Provider A MPLS/GMPLS network
        Authorized but untrusted neighbor: provider B
        Unauthorized neighbors: CE1, CE2

          Figure 2: MPLS/GMPLS Trusted Zone and Authorized Neighbor

   All aspects of network security independent of whether a network is
   an MPLS/GMPLS network, are out of scope.  For example, attacks from
   the Internet to a user's web-server connected through the MPLS/GMPLS
   network are not considered here, unless the way the MPLS/GMPLS
   network is provisioned could make a difference to the security of
   this user's server.

4.  Security Threats

   This section discusses the various network security threats that may
   endanger MPLS/GMPLS networks.  RFC 4778 [RFC4778] provided the best
   current operational security practices in Internet Service Provider
   environments.

   A successful attack on a particular MPLS/GMPLS network or on an SP's
   MPLS/GMPLS infrastructure may cause one or more of the following ill
   effects:

   -  Observation, modification, or deletion of a provider's or user's
      data.

   -  Replay of a provider's or user's data.

   -  Injection of inauthentic data into a provider's or user's traffic
      stream.

   -  Traffic pattern analysis on a provider's or user's traffic.

   -  Disruption of a provider's or user's connectivity.



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   -  Degradation of a provider's service quality.

   -  Probing a provider's network to determine its configuration,
      capacity, or usage.

   It is useful to consider that threats, whether malicious or
   accidental, may come from different categories of sources.  For
   example, they may come from:

   -  Other users whose services are provided by the same MPLS/GMPLS
      core.

   -  The MPLS/GMPLS SP or persons working for it.

   -  Other persons who obtain physical access to an MPLS/GMPLS SP's
      site.

   -  Other persons who use social engineering methods to influence the
      behavior of an SP's personnel.

   -  Users of the MPLS/GMPLS network itself, e.g., intra-VPN threats.
      (Such threats are beyond the scope of this document.)

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

   -  Other SPs in the case of MPLS/GMPLS inter-provider connection.
      The core of the other provider may or may not be using MPLS/GMPLS.

   -  Those who create, deliver, install, and maintain software for
      network equipment.

   Given that security is generally a tradeoff between expense and risk,
   it is also useful to consider the likelihood of different attacks
   occurring.  There is at least a perceived difference in the
   likelihood of most types of attacks being successfully mounted in
   different environments, such as:

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

   -  An MPLS/GMPLS configuration transiting the public Internet.

   Most types of attacks become easier to mount and hence more likely as
   the shared infrastructure via which service is provided expands from
   a single SP to multiple cooperating SPs to the global Internet.
   Attacks that may not be of sufficient likeliness to warrant concern
   in a closely controlled environment often merit defensive measures in
   broader, more open environments.  In closed communities, it is often




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   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.



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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.)






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

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

   This includes unauthorized access to an SP's infrastructure
   equipment, for example, to reconfigure the equipment or to extract
   information (statistics, topology, etc.) pertaining to the network.

4.1.7.  Cross-Connection of Traffic between Users

   This refers to the event in which expected isolation between separate
   users (who may be VPN users) is breached.  This includes cases such
   as:

   -  A site being connected into the "wrong" VPN.

   -  Traffic being replicated and sent to an unauthorized user.

   -  Two or more VPNs being improperly merged together.

   -  A point-to-point VPN connecting the wrong two points.

   -  Any packet or frame being improperly delivered outside the VPN to
      which it belongs

   Misconnection or cross-connection of VPNs may be caused by service
   provider or equipment vendor error, or by the malicious action of an
   attacker.  The breach may be physical (e.g., PE-CE links
   misconnected) or logical (e.g., improper device configuration).

   Anecdotal evidence suggests that the cross-connection threat is one
   of the largest security concerns of users (or would-be users).

4.1.8.  Attacks against Routing Protocols

   This encompasses attacks against underlying routing protocols that
   are run by the SP and that directly support the MPLS/GMPLS core.
   (Attacks against the use of routing protocols for the distribution of
   backbone routes are beyond the scope of this document.)  Specific
   attacks against popular routing protocols have been widely studied
   and are described in [RFC4593].







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4.1.9.  Other Attacks on Control Traffic

   Besides routing and management protocols (covered separately in the
   previous sections), a number of other control protocols may be
   directly involved in delivering services by the MPLS/GMPLS core.
   These include but may not be limited to:

   -  MPLS signaling (LDP, RSVP-TE) discussed above in subsections 4.1.4
      and 4.1.3

   -  PCE signaling

   -  IPsec signaling (IKE and IKEv2)

   -  ICMP and ICMPv6

   -  L2TP

   -  BGP-based membership discovery

   -  Database-based membership discovery (e.g., RADIUS)

   -  Other protocols that may be important to the control
      infrastructure, e.g., DNS, LMP, NTP, SNMP, and GRE.

   Attacks might subvert or disrupt the activities of these protocols,
   for example via impersonation or DoS.

   Note that all of the data-plane attacks can also be carried out
   against the packets of the control and management planes: insertion,
   spoofing, replay, deletion, pattern analysis, and other attacks
   mentioned above.

4.2.  Attacks on the Data Plane

   This category encompasses attacks on the provider's or end-user's
   data.  Note that from the MPLS/GMPLS network end user's point of
   view, some of this might be control-plane traffic, e.g., routing
   protocols running from user site A to user site B via IP or non-IP
   connections, which may be some type of VPN.

4.2.1.  Unauthorized Observation of Data Traffic

   This refers to "sniffing" provider or end user packets and examining
   their contents.  This can result in exposure of confidential
   information.  It can also be a first step in other attacks (described
   below) in which the recorded data is modified and re-inserted, or
   simply replayed later.



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4.2.2.  Modification of Data Traffic

   This refers to modifying the contents of packets as they traverse the
   MPLS/GMPLS core.

4.2.3.  Insertion of Inauthentic Data Traffic: Spoofing and Replay

   Spoofing refers to sending a user packets or inserting packets into a
   data stream that do not belong, with the objective of having them
   accepted by the recipient as legitimate.  Also included in this
   category is the insertion of copies of once-legitimate packets that
   have been recorded and replayed.

4.2.4.  Unauthorized Deletion of Data Traffic

   This refers to causing packets to be discarded as they traverse the
   MPLS/GMPLS networks.  This is a specific type of denial-of-service
   attack.

4.2.5.  Unauthorized Traffic Pattern Analysis

   This refers to "sniffing" provider or user packets and examining
   aspects or meta-aspects of them that may be visible even when the
   packets themselves are encrypted.  An attacker might gain useful
   information based on the amount and timing of traffic, packet sizes,
   source and destination addresses, etc.  For most users, this type of
   attack is generally considered to be significantly less of a concern
   than the other types discussed in this section.

4.2.6.  Denial-of-Service Attacks

   Denial-of-service (DoS) attacks are those in which an attacker
   attempts to disrupt or prevent the use of a service by its legitimate
   users.  Taking network devices out of service, modifying their
   configuration, or overwhelming them with requests for service are
   several of the possible avenues for DoS attack.

   Overwhelming the network with requests for service, otherwise known
   as a "resource exhaustion" DoS attack, may target any resource in the
   network, e.g., link bandwidth, packet forwarding capacity, session
   capacity for various protocols, CPU power, table size, storage
   overflows, and so on.

   DoS attacks of the resource exhaustion type can be mounted against
   the data plane of a particular provider or end user by attempting to
   insert (spoofing) an overwhelming quantity of inauthentic data into
   the provider or end-user's network from outside of the trusted zone.
   Potential results might be to exhaust the bandwidth available to that



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   provider or end user, or to overwhelm the cryptographic
   authentication mechanisms of the provider or end user.

   Data-plane resource exhaustion attacks can also be mounted by
   overwhelming the service provider's general (MPLS/GMPLS-independent)
   infrastructure with traffic.  These attacks on the general
   infrastructure are not usually an MPLS/GMPLS-specific issue, unless
   the attack is mounted by another MPLS/GMPLS network user from a
   privileged position.  (For example, an MPLS/GMPLS network user might
   be able to monopolize network data-plane resources and thus disrupt
   other users.)

   Many DoS attacks use amplification, whereby the attacker co-opts
   otherwise innocent parties to increase the effect of the attack.  The
   attacker may, for example, send packets to a broadcast or multicast
   address with the spoofed source address of the victim, and all of the
   recipients may then respond to the victim.

4.2.7.  Misconnection

   Misconnection may arise through deliberate attack, or through
   misconfiguration or misconnection of the network resources.  The
   result is likely to be delivery of data to the wrong destination or
   black-holing of the data.

   In GMPLS with physically diverse control and data planes, it may be
   possible for data-plane misconnection to go undetected by the control
   plane.

   In optical networks under GMPLS control, misconnection may give rise
   to physical safety risks as unprotected lasers may be activated
   without warning.

4.3.  Attacks on Operation and Management Plane

   Attacks on the Operation and Management plane have been discussed
   extensively as general network security issues over the last 20
   years.  RFC 4778 [RFC4778] may serve as the best current operational
   security practices in Internet Service Provider environments.  RFC
   4377 [RFC4377] provided Operations and Management Requirements for
   MPLS networks.  See also the Security Considerations of RFC 4377 and
   Section 7 of RFC 4378 [RFC4378].

   Operation and Management across the MPLS-ICI could also be the source
   of security threats on the provider infrastructure as well as the
   service offered over the MPLS-ICI.  A large volume of Operation and
   Management messages could overwhelm the processing capabilities of an
   ASBR if the ASBR is not properly protected.  Maliciously generated



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   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





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   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,



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   protocol designers need to provide a full set of security services,
   which can be used where appropriate.

   The techniques discussed here include encryption, authentication,
   filtering, firewalls, access control, isolation, aggregation, and
   others.

   Often, security is achieved by careful protocol design, rather than
   by adding a security method.  For example, one method of mitigating
   DoS attacks is to make sure that innocent parties cannot be used to
   amplify the attack.  Security works better when it is "designed in"
   rather than "added on".

   Nothing is ever 100% secure.  Defense therefore involves protecting
   against those attacks that are most likely to occur or that have the
   most direct consequences if successful.  For those attacks that are
   protected against, absolute protection is seldom achievable; more
   often it is sufficient just to make the cost of a successful attack
   greater than what the adversary will be willing or able to expend.

   Successfully defending against an attack does not necessarily mean
   the attack must be prevented from happening or from reaching its
   target.  In many cases, the network can instead be designed to
   withstand the attack.  For example, the introduction of inauthentic
   packets could be defended against by preventing their introduction in
   the first place, or by making it possible to identify and eliminate
   them before delivery to the MPLS/GMPLS user's system.  The latter is
   frequently a much easier task.

5.1.  Authentication

   To prevent security issues arising from some DoS attacks or from
   malicious or accidental misconfiguration, it is critical that devices
   in the MPLS/GMPLS should only accept connections or control messages
   from valid sources.  Authentication refers to methods to ensure that
   message sources are properly identified by the MPLS/GMPLS devices
   with which they communicate.  This section focuses on identifying the
   scenarios in which sender authentication is required and recommends
   authentication mechanisms for these scenarios.

   Cryptographic techniques (authentication, integrity, and encryption)
   do not protect against some types of denial-of-service attacks,
   specifically resource exhaustion attacks based on CPU or bandwidth
   exhaustion.  In fact, the software-based cryptographic processing
   required to decrypt or check authentication may in some cases
   increase the effect of these resource exhaustion attacks.  With a
   hardware cryptographic accelerator, attack packets can be dropped at
   line speed without a cost to software cycles.  Cryptographic



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

   The MPLS data plane, as presently defined, is not amenable to source
   authentication, as there are no source identifiers in the MPLS packet
   to authenticate.  The MPLS label is only locally meaningful.  It may
   be assigned by a downstream node or upstream node for multicast
   support.

   When the MPLS payload carries identifiers that may be authenticated
   (e.g., IP packets), authentication may be carried out at the client
   level, but this does not help the MPLS SP, as these client
   identifiers belong to an external, untrusted network.

5.1.1.  Management System Authentication

   Management system authentication includes the authentication of a PE
   to a centrally managed network management or directory server when
   directory-based "auto-discovery" is used.  It also includes
   authentication of a CE to the configuration server, when a
   configuration server system is used.

   Authentication should be bidirectional, including PE or CE to
   configuration server authentication for the PE or CE to be certain it
   is communicating with the right server.

5.1.2.  Peer-to-Peer Authentication

   Peer-to-peer authentication includes peer authentication for network
   control protocols (e.g., LDP, BGP, etc.) and other peer
   authentication (i.e., authentication of one IPsec security gateway by
   another).

   Authentication should be bidirectional, including PE or CE to
   configuration server authentication for the PE or CE to be certain it
   is communicating with the right server.

   As indicated in Section 5.1.1, authentication should be
   bidirectional.

5.1.3.  Cryptographic Techniques for Authenticating Identity

   Cryptographic techniques offer several mechanisms for authenticating
   the identity of devices or individuals.  These include the use of
   shared secret keys, one-time keys generated by accessory devices or
   software, user-ID and password pairs, and a range of public-private




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   key systems.  Another approach is to use a hierarchical Certification
   Authority system to provide digital certificates.

   This section describes or provides references to the specific
   cryptographic approaches for authenticating identity.  These
   approaches provide secure mechanisms for most of the authentication
   scenarios required in securing an MPLS/GMPLS network.

5.2.  Cryptographic Techniques

   MPLS/GMPLS defenses against a wide variety of attacks can be enhanced
   by the proper application of cryptographic techniques.  These same
   cryptographic techniques are applicable to general network
   communications and can provide confidentiality (encryption) of
   communication between devices, authenticate the identities of the
   devices, and detect whether the data being communicated has been
   changed during transit or replayed from previous messages.

   Several aspects of authentication are addressed in some detail in a
   separate "Authentication" section (Section 5.1).

   Cryptographic methods add complexity to a service and thus, for a few
   reasons, may not be the most practical solution in every case.
   Cryptography adds an additional computational burden to devices,
   which may reduce the number of user connections that can be handled
   on a device or otherwise reduce the capacity of the device,
   potentially driving up the provider's costs.  Typically, configuring
   encryption services on devices adds to the complexity of their
   configuration and adds labor cost.  Some key management system is
   usually needed.  Packet sizes are typically increased when the
   packets are encrypted or have integrity checks or replay counters
   added, increasing the network traffic load and adding to the
   likelihood of packet fragmentation with its increased overhead.
   (This packet length increase can often be mitigated to some extent by
   data compression techniques, but at the expense of additional
   computational burden.) Finally, some providers may employ enough
   other defensive techniques, such as physical isolation or filtering
   and firewall techniques, that they may not perceive additional
   benefit from encryption techniques.

   Users may wish to provide confidentiality end to end.  Generally,
   encrypting for confidentiality must be accompanied with cryptographic
   integrity checks to prevent certain active attacks against the
   encrypted communications.  On today's processors, encryption and
   integrity checks run extremely quickly, but key management may be
   more demanding in terms of both computational and administrative
   overhead.




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   The trust model among the MPLS/GMPLS user, the MPLS/GMPLS provider,
   and other parts of the network is a major element in determining the
   applicability of cryptographic protection for any specific MPLS/GMPLS
   implementation.  In particular, it determines where cryptographic
   protection should be applied:

   -  If the data path between the user's site and the provider's PE is
      not trusted, then it may be used on the PE-CE link.

   -  If some part of the backbone network is not trusted, particularly
      in implementations where traffic may travel across the Internet or
      multiple providers' networks, then the PE-PE traffic may be
      cryptographically protected.  One also should consider cases where
      L1 technology may be vulnerable to eavesdropping.

   -  If the user does not trust any zone outside of its premises, it
      may require end-to-end or CE-CE cryptographic protection.  This
      fits within the scope of this MPLS/GMPLS security framework when
      the CE is provisioned by the MPLS/GMPLS provider.

   -  If the user requires remote access to its site from a system at a
      location that is not a customer location (for example, access by a
      traveler), there may be a requirement for cryptographically
      protecting the traffic between that system and an access point or
      a customer's site.  If the MPLS/GMPLS provider supplies the access
      point, then the customer must cooperate with the provider to
      handle the access control services for the remote users.  These
      access control services are usually protected cryptographically,
      as well.

   Access control usually starts with authentication of the entity.  If
   cryptographic services are part of the scenario, then it is important
   to bind the authentication to the key management.  Otherwise, the
   protocol is vulnerable to being hijacked between the authentication
   and key management.

   Although CE-CE cryptographic protection can provide integrity and
   confidentiality against third parties, if the MPLS/GMPLS provider has
   complete management control over the CE (encryption) devices, then it
   may be possible for the provider to gain access to the user's traffic
   or internal network.  Encryption devices could potentially be
   reconfigured to use null encryption, bypass cryptographic processing
   altogether, reveal internal configuration, or provide some means of
   sniffing or diverting unencrypted traffic.  Thus an implementation
   using CE-CE encryption needs to consider the trust relationship
   between the MPLS/GMPLS user and provider.  MPLS/GMPLS users and
   providers may wish to negotiate a service level agreement (SLA) for
   CE-CE encryption that provides an acceptable demarcation of



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   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,



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   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.







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5.2.3.  Encryption for Device Configuration and Management

   For configuration and management of MPLS/GMPLS devices, encryption
   and authentication of the management connection at a level comparable
   to that provided by IPsec is desirable.

   Several methods of transporting MPLS/GMPLS device management traffic
   offer authentication, integrity, and confidentiality.

   -  Secure Shell (SSH) offers protection for TELNET [STD8] or
      terminal-like connections to allow device configuration.

   -  SNMPv3 [STD62] provides encrypted and authenticated protection for
      SNMP-managed devices.

   -  Transport Layer Security (TLS) [RFC5246] and the closely-related
      Secure Sockets Layer (SSL) are widely used for securing HTTP-based
      communication, and thus can provide support for most XML- and
      SOAP-based device management approaches.

   -  Since 2004, there has been extensive work proceeding in several
      organizations (OASIS, W3C, WS-I, and others) on securing device
      management traffic within a "Web Services" framework, using a wide
      variety of security models, and providing support for multiple
      security token formats, multiple trust domains, multiple signature
      formats, and multiple encryption technologies.

   -  IPsec provides security services including integrity and
      confidentiality at the network layer.  With regards to device
      management, its current use is primarily focused on in-band
      management of user-managed IPsec gateway devices.

   -  There is recent work in the ISMS WG (Integrated Security Model for
      SNMP Working Group) to define how to use SSH to secure SNMP, due
      to the limited deployment of SNMPv3, and the possibility of using
      Kerberos, particularly for interfaces like TELNET, where client
      code exists.

5.2.4.  Security Considerations for MPLS Pseudowires

   In addition to IP traffic, MPLS networks may be used to transport
   other services such as Ethernet, ATM, Frame Relay, and TDM.  This is
   done by setting up pseudowires (PWs) that tunnel the native service
   through the MPLS core by encapsulating at the edges.  The PWE
   architecture is defined in [RFC3985].






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   PW tunnels may be set up using the PWE control protocol based on LDP
   [RFC4447], and thus security considerations for LDP will most likely
   be applicable to the PWE3 control protocol as well.

   PW user packets contain at least one MPLS label (the PW label) and
   may contain one or more MPLS tunnel labels.  After the label stack,
   there is a four-byte control word (which is optional for some PW
   types), followed by the native service payload.  It must be stressed
   that encapsulation of MPLS PW packets in IP for the purpose of
   enabling use of IPsec mechanisms is not a valid option.

   The following is a non-exhaustive list of PW-specific threats:

   -  Unauthorized setup of a PW (e.g., to gain access to a customer
      network)

   -  Unauthorized teardown of a PW (thus causing denial of service)

   -  Malicious reroute of a PW

   -  Unauthorized observation of PW packets

   -  Traffic analysis of PW connectivity

   -  Unauthorized insertion of PW packets

   -  Unauthorized modification of PW packets

   -  Unauthorized deletion of PW packets replay of PW packets

   -  Denial of service or significant impact on PW service quality

   These threats are not mutually exclusive, for example, rerouting can
   be used for snooping or insertion/deletion/replay, etc.  Multisegment
   PWs introduce additional weaknesses at their stitching points.

   The PW user plane suffers from the following inherent security
   weaknesses:

   -  Since the PW label is the only identifier in the packet, there is
      no authenticatable source address.

   -  Since guessing a valid PW label is not difficult, it is relatively
      easy to introduce seemingly valid foreign packets.

   -  Since the PW packet is not self-describing, minor modification of
      control-plane packets renders the data-plane traffic useless.




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   -  The control-word sequence number processing algorithm is
      susceptible to a DoS attack.

   The PWE control protocol introduces its own weaknesses:

   -  No (secure) peer autodiscovery technique has been standardized .

   -  PE authentication is not mandated, so an intruder can potentially
      impersonate a PE; after impersonating a PE, unauthorized PWs may
      be set up, consuming resources and perhaps allowing access to user
      networks.

   -  Alternately, desired PWs may be torn down, giving rise to denial
      of service.

   The following characteristics of PWs can be considered security
   strengths:

   -  The most obvious attacks require compromising edge or core routers
      (although not necessarily those along the PW path).

   -  Adequate protection of the control-plane messaging is sufficient
      to rule out many types of attacks.

   -  PEs are usually configured to reject MPLS packets from outside the
      service provider network, thus ruling out insertion of PW packets
      from the outside (since IP packets cannot masquerade as PW
      packets).

5.2.5.  End-to-End versus Hop-by-Hop Protection Tradeoffs in MPLS/GMPLS

   In MPLS/GMPLS, cryptographic protection could potentially be applied
   to the MPLS/GMPLS traffic at several different places.  This section
   discusses some of the tradeoffs in implementing encryption in several
   different connection topologies among different devices within an
   MPLS/GMPLS network.

   Cryptographic protection typically involves a pair of devices that
   protect the traffic passing between them.  The devices may be
   directly connected (over a single "hop"), or intervening devices may
   transport the protected traffic between the pair of devices.  The
   extreme cases involve using protection between every adjacent pair of
   devices along a given path (hop-by-hop), or using protection only
   between the end devices along a given path (end-to-end).  To keep
   this discussion within the scope of this document, the latter ("end-
   to-end") case considered here is CE-to-CE rather than fully end-to-
   end.




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   Figure 3 depicts a simplified topology showing the Customer Edge (CE)
   devices, the Provider Edge (PE) devices, and a variable number (three
   are shown) of Provider core (P) devices, which might be present along
   the path between two sites in a single VPN operated by a single
   service provider (SP).

   Site_1---CE---PE---P---P---P---PE---CE---Site_2

   Figure 3: Simplified Topology Traversing through MPLS/GMPLS Core

   Within this simplified topology, and assuming that the P devices are
   not involved with cryptographic protection, four basic, feasible
   configurations exist for protecting connections among the devices:

   1) Site-to-site (CE-to-CE) - Apply confidentiality or integrity
      services between the two CE devices, so that traffic will be
      protected throughout the SP's network.

   2) Provider edge-to-edge (PE-to-PE) - Apply confidentiality or
      integrity services between the two PE devices.  Unprotected
      traffic is received at one PE from the customer's CE, then it is
      protected for transmission through the SP's network to the other
      PE, and finally it is decrypted or checked for integrity and sent
      to the other CE.

   3) Access link (CE-to-PE) - Apply confidentiality or integrity
      services between the CE and PE on each side or on only one side.

   4) Configurations 2 and 3 above can also be combined, with
      confidentiality or integrity running from CE to PE, then PE to PE,
      and then PE to CE.

   Among the four feasible configurations, key tradeoffs in considering
   encryption include:

   -  Vulnerability to link eavesdropping or tampering - assuming an
      attacker can observe or modify data in transit on the links, would
      it be protected by encryption?

   -  Vulnerability to device compromise - assuming an attacker can get
      access to a device (or freely alter its configuration), would the
      data be protected?

   -  Complexity of device configuration and management - given the
      number of sites per VPN customer as Nce and the number of PEs
      participating in a given VPN as Npe, how many device
      configurations need to be created or maintained, and how do those
      configurations scale?



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   -  Processing load on devices - how many cryptographic operations
      must be performed given N packets? - This raises considerations of
      device capacity and perhaps end-to-end delay.

   -  Ability of the SP to provide enhanced services (QoS, firewall,
      intrusion detection, etc.) - Can the SP inspect the data to
      provide these services?

   These tradeoffs are discussed for each configuration, below:

   1) Site-to-site (CE-to-CE)

   Link eavesdropping or tampering - protected on all links.  Device
   compromise - vulnerable to CE compromise.

   Complexity - single administration, responsible for one device per
         site (Nce devices), but overall configuration per VPN scales as
         Nce**2.

         Though the complexity may be reduced: 1) In practice, as Nce
         grows, the number of VPNs falls off from being a full clique;
         2) If the CEs run an automated key management protocol, then
         they should be able to set up and tear down secured VPNs
         without any intervention.

   Processing load - on each of the two CEs, each packet is
         cryptographically processed (2P), though the protection may be
         "integrity check only" or "integrity check plus encryption."

   Enhanced services - severely limited; typically only Diffserv
         markings are visible to the SP, allowing some QoS services.
         The CEs could also use the IPv6 Flow Label to identify traffic
         classes.

   2) Provider Edge-to-Edge (PE-to-PE)

   Link eavesdropping or tampering - vulnerable on CE-PE links;
         protected on SP's network links.

   Device compromise - vulnerable to CE or PE compromise.

   Complexity - single administration, Npe devices to configure.
         (Multiple sites may share a PE device so Npe is typically much
         smaller than Nce.)  Scalability of the overall configuration
         depends on the PPVPN type: if the cryptographic protection is
         separate per VPN context, it scales as Npe**2 per customer VPN.
         If it is per-PE, it scales as Npe**2 for all customer VPNs
         combined.



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   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.







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   Given the tradeoffs discussed above, a few conclusions can be drawn:

   -  Configurations 2 and 3 are subsets of 4 that may be appropriate
      alternatives to 4 under certain threat models; the remainder of
      these conclusions compare 1 (CE-to-CE) versus 4 (combined access
      links and PE-to-PE).

   -  If protection from link eavesdropping or tampering is all that is
      important, then configurations 1 and 4 are equivalent.

   -  If protection from device compromise is most important and the
      threat is to the CE devices, both cases are equivalent; if the
      threat is to the PE devices, configuration 1 is better.

   -  If reducing complexity is most important, and the size of the
      network is small, configuration 1 is better.  Otherwise,
      configuration 4 is better because rather than a mesh of CE
      devices, it requires a smaller mesh of PE devices.  Also, under
      some PPVPN approaches, the scaling of 4 is further improved by
      sharing the same PE-PE mesh across all VPN contexts.  The scaling
      advantage of 4 may be increased or decreased in any given
      situation if the CE devices are simpler to configure than the PE
      devices, or vice-versa.

   -  If the overall processing load is a key factor, then 1 is better,
      unless the PEs come with a hardware encryption accelerator and the
      CEs do not.

   -  If the availability of enhanced services support from the SP is
      most important, then 4 is best.

   -  If users are concerned with having their VPNs misconnected with
      other users' VPNs, then encryption with 1 can provide protection.

   As a quick overall conclusion, CE-to-CE protection is better against
   device compromise, but this comes at the cost of enhanced services
   and at the cost of operational complexity due to the Order(n**2)
   scaling of a larger mesh.

   This analysis of site-to-site vs. hop-by-hop tradeoffs does not
   explicitly include cases of multiple providers cooperating to provide
   a PPVPN service, public Internet VPN connectivity, or remote access
   VPN service, but many of the tradeoffs are similar.








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   In addition to the simplified models, the following should also be
   considered:

   -  There are reasons, perhaps, to protect a specific P-to-P or PE-
      to-P.

   -  There may be reasons to do multiple encryptions over certain
      segments.  One may be using an encrypted wireless link under our
      IPsec VPN to access an SSL-secured web site to download encrypted
      email attachments: four layers.)

   -  It may be appropriate that, for example, cryptographic integrity
      checks are applied end to end, and confidentiality is applied over
      a shorter span.

   -  Different cryptographic protection may be required for control
      protocols and data traffic.

   -  Attention needs to be given to how auxiliary traffic is protected,
      e.g., the ICMPv6 packets that flow back during PMTU discovery,
      among other examples.

5.3.  Access Control Techniques

   Access control techniques include packet-by-packet or packet-flow-
   by-packet-flow access control by means of filters and firewalls on
   IPv4/IPv6 packets, as well as by means of admitting a "session" for a
   control, signaling, or management protocol.  Enforcement of access
   control by isolated infrastructure addresses is discussed in Section
   5.4 of this document.

   In this document, we distinguish between filtering and firewalls
   based primarily on the direction of traffic flow.  We define
   filtering as being applicable to unidirectional traffic, while a
   firewall can analyze and control both sides of a conversation.

   The definition has two significant corollaries:

   -  Routing or traffic flow symmetry: A firewall typically requires
      routing symmetry, which is usually enforced by locating a firewall
      where the network topology assures that both sides of a
      conversation will pass through the firewall.  A filter can operate
      upon traffic flowing in one direction, without considering traffic
      in the reverse direction.  Beware that this concept could result
      in a single point of failure.






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   -  Statefulness: Because it receives both sides of a conversation, a
      firewall may be able to interpret a significant amount of
      information concerning the state of that conversation and use this
      information to control access.  A filter can maintain some limited
      state information on a unidirectional flow of packets, but cannot
      determine the state of the bidirectional conversation as precisely
      as a firewall.

   For a general description on filtering and rate limiting for IP
   networks, please also see [OPSEC-FILTER].

5.3.1.  Filtering

   It is relatively common for routers to filter packets.  That is,
   routers can look for particular values in certain fields of the IP or
   higher-level (e.g., TCP or UDP) headers.  Packets matching the
   criteria associated with a particular filter may either be discarded
   or given special treatment.  Today, not only routers, but most end
   hosts have filters, and every instance of IPsec is also a filter
   [RFC4301].

   In discussing filters, it is useful to separate the filter
   characteristics that may be used to determine whether a packet
   matches a filter from the packet actions applied to those packets
   matching a particular filter.

   o  Filter Characteristics

   Filter characteristics or rules are used to determine whether a
   particular packet or set of packets matches a particular filter.

   In many cases, filter characteristics may be stateless.  A stateless
   filter determines whether a particular packet matches a filter based
   solely on the filter definition, normal forwarding information (such
   as the next hop for a packet), the interface on which a packet
   arrived, and the contents of that individual packet.  Typically,
   stateless filters may consider the incoming and outgoing logical or
   physical interface, information in the IP header, and information in
   higher-layer headers such as the TCP or UDP header.  Information in
   the IP header to be considered may for example include source and
   destination IP addresses; Protocol field, Fragment Offset, and TOS
   field in IPv4; or Next Header, Extension Headers, Flow label, etc. in
   IPv6.  Filters also may consider fields in the TCP or UDP header such
   as the Port numbers, the SYN field in the TCP header, as well as ICMP
   and ICMPv6 type.






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   Stateful filtering maintains packet-specific state information to aid
   in determining whether a filter rule has been met.  For example, a
   device might apply stateless filtering to the first fragment of a
   fragmented IPv4 packet.  If the filter matches, then the data unit ID
   may be remembered and other fragments of the same packet may then be
   considered to match the same filter.  Stateful filtering is more
   commonly done in firewalls, although firewall technology may be added
   to routers.  The data unit ID can also be a Fragment Extension Header
   Identification field in IPv6.

   o Actions based on Filter Results

   If a packet, or a series of packets, matches a specific filter, then
   a variety of actions may be taken based on that match.  Examples of
   such actions include:

      -  Discard

         In many cases, filters are set to catch certain undesirable
         packets.  Examples may include packets with forged or invalid
         source addresses, packets that are part of a DoS or Distributed
         DoS (DDoS) attack, or packets trying to access unallowed
         resources (such as network management packets from an
         unauthorized source).  Where such filters are activated, it is
         common to discard the packet or set of packets matching the
         filter silently.  The discarded packets may of course also be
         counted or logged.

      -  Set CoS

         A filter may be used to set the class of service associated
         with the packet.

      -  Count packets or bytes

      -  Rate Limit

         In some cases, the set of packets matching a particular filter
         may be limited to a specified bandwidth.  In this case, packets
         or bytes would be counted, and would be forwarded normally up
         to the specified limit.  Excess packets may be discarded or may
         be marked (for example, by setting a "discard eligible" bit in
         the IPv4 ToS field, or changing the EXP value to identify
         traffic as being out of contract).







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      - 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



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   MPLS/GMPLS user sites, but typically other defensive techniques will
   be used for this purpose.

   Where firewalls are employed as a service to protect user VPN sites
   from the Internet, different VPN users, and even different sites of a
   single VPN user, may have varying firewall requirements.  The overall
   PPVPN logical and physical topology, along with the capabilities of
   the devices implementing the firewall services, has a significant
   effect on the feasibility and manageability of such varied firewall
   service offerings.

   Another consideration with the use of firewalls is that they can
   provide few options for handling packets carrying encrypted data.
   Because the data itself is not accessible, only packet header
   information, other unencrypted fields, or analysis of the flow of
   encrypted packets can be used for making decisions on accepting or
   rejecting encrypted traffic.

   Two approaches of using firewalls are to move the firewall outside of
   the encrypted part of the path or to register and pre-approve the
   encrypted session with the firewall.

   Handling DoS attacks has become increasingly important.  Useful
   guidelines include the following:

   1. Perform ingress filtering everywhere.

   2. Be able to filter DoS attack packets at line speed.

   3. Do not allow oneself to amplify attacks.

   4. Continue processing legitimate traffic.  Over provide for heavy
      loads.  Use diverse locations, technologies, etc.

5.3.3.  Access Control to Management Interfaces

   Most of the security issues related to management interfaces can be
   addressed through the use of authentication techniques as described
   in the section on authentication (Section 5.1).  However, additional
   security may be provided by controlling access to management
   interfaces in other ways.

   The Optical Internetworking Forum has done relevant work on
   protecting such interfaces with TLS, SSH, Kerberos, IPsec, WSS, etc.
   See "Security for Management Interfaces to Network Elements"
   [OIF-SMI-01.0] and "Addendum to the Security for Management
   Interfaces to Network Elements" [OIF-SMI-02.1].  See also the work in
   the ISMS WG (http://datatracker.ietf.org/wg/isms/charter/).



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   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,



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   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




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   much ensures that there is no unintended connectivity to some other
   site.

5.8.  Verification of Connectivity

   In order to protect against deliberate or accidental misconnection,
   mechanisms can be put in place to verify both end-to-end connectivity
   and hop-by-hop resources.  These mechanisms can trace the routes of
   LSPs in both the control plane and the data plane.

   It should be noted that if there is an attack on the control plane,
   data-plane connectivity test mechanisms that rely on the control
   plane can also be attacked.  This may hide faults through false
   positives or disrupt functioning services through false negatives.

6.  Monitoring, Detection, and Reporting of Security Attacks

   MPLS/GMPLS network and service may be subject to attacks from a
   variety of security threats.  Many threats are described in Section 4
   of this document.  Many of the defensive techniques described in this
   document and elsewhere provide significant levels of protection from
   a variety of threats.  However, in addition to employing defensive
   techniques silently to protect against attacks, MPLS/GMPLS services
   can also add value for both providers and customers by implementing
   security monitoring systems to detect and report on any security
   attacks, regardless of whether the attacks are effective.

   Attackers often begin by probing and analyzing defenses, so systems
   that can detect and properly report these early stages of attacks can
   provide significant benefits.

   Information concerning attack incidents, especially if available
   quickly, can be useful in defending against further attacks.  It can
   be used to help identify attackers or their specific targets at an
   early stage.  This knowledge about attackers and targets can be used
   to strengthen defenses against specific attacks or attackers, or to
   improve the defenses for specific targets on an as-needed basis.
   Information collected on attacks may also be useful in identifying
   and developing defenses against novel attack types.

   Monitoring systems used to detect security attacks in MPLS/GMPLS
   typically operate by collecting information from the Provider Edge
   (PE), Customer Edge (CE), and/or Provider backbone (P) devices.
   Security monitoring systems should have the ability to actively
   retrieve information from devices (e.g., SNMP get) or to passively
   receive reports from devices (e.g., SNMP notifications).  The systems
   may actively retrieve information from devices (e.g., SNMP get) or
   passively receive reports from devices (e.g., SNMP notifications).



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   The specific information exchanged depends on the capabilities of the
   devices and on the type of VPN technology.  Particular care should be
   given to securing the communications channel between the monitoring
   systems and the MPLS/GMPLS devices.

   The CE, PE, and P devices should employ efficient methods to acquire
   and communicate the information needed by the security monitoring
   systems.  It is important that the communication method between
   MPLS/GMPLS devices and security monitoring systems be designed so
   that it will not disrupt network operations.  As an example, multiple
   attack events may be reported through a single message, rather than
   allowing each attack event to trigger a separate message, which might
   result in a flood of messages, essentially becoming a DoS attack
   against the monitoring system or the network.


   The mechanisms for reporting security attacks should be flexible
   enough to meet the needs of MPLS/GMPLS service providers, MPLS/GMPLS
   customers, and regulatory agencies, if applicable.  The specific
   reports should depend on the capabilities of the devices, the
   security monitoring system, the type of VPN, and the service level
   agreements between the provider and customer.

   While SNMP/syslog type monitoring and detection mechanisms can detect
   some attacks (usually resulting from flapping protocol adjacencies,
   CPU overload scenarios, etc.), other techniques, such as netflow-
   based traffic fingerprinting, are needed for more detailed detection
   and reporting.

   With netflow-based traffic fingerprinting, each packet that is
   forwarded within a device is examined for a set of IP packet
   attributes.  These attributes are the IP packet identity or
   fingerprint of the packet and determine if the packet is unique or
   similar to other packets.

   The flow information is extremely useful for understanding network
   behavior, and detecting and reporting security attacks:

   -  Source address allows the understanding of who is originating the
      traffic.

   -  Destination address tells who is receiving the traffic.

   -  Ports characterize the application utilizing the traffic.

   -  Class of service examines the priority of the traffic.





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

   -  Tallied packets and bytes show the amount of traffic.

   -  Flow timestamps allow the understanding of the life of a flow;
      timestamps are useful for calculating packets and bytes per
      second.

   -  Next-hop IP addresses including BGP routing Autonomous Systems
      (ASes).

   -  Subnet mask for the source and destination addresses are for
      calculating prefixes.

   -  TCP flags are useful for examining TCP handshakes.

7.  Service Provider General Security Requirements

   This section covers security requirements the provider may have for
   securing its MPLS/GMPLS network infrastructure including LDP and
   RSVP-TE-specific requirements.

   The MPLS/GMPLS service provider's requirements defined here are for
   the MPLS/GMPLS core in the reference model.  The core network can be
   implemented with different types of network technologies, and each
   core network may use different technologies to provide the various
   services to users with different levels of offered security.
   Therefore, an MPLS/GMPLS service provider may fulfill any number of
   the security requirements listed in this section.  This document does
   not state that an MPLS/GMPLS network must fulfill all of these
   requirements to be secure.

   These requirements are focused on: 1) how to protect the MPLS/GMPLS
   core from various attacks originating outside the core including
   those from network users, both accidentally and maliciously, and 2)
   how to protect the end users.

7.1.  Protection within the Core Network

7.1.1.  Control-Plane Protection - General

   -  Filtering spoofed infrastructure IP addresses at edges

   Many attacks on protocols running in a core involve spoofing a source
   IP address of a node in the core (e.g., TCP-RST attacks).  It makes
   sense to apply anti-spoofing filtering at edges, e.g., using strict
   unicast reverse path forwarding (uRPF) [RFC3704] and/or by preventing



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   the use of infrastructure addresses as source.  If this is done
   comprehensively, the need to cryptographically secure these protocols
   is smaller.  See [BACKBONE-ATTKS] for more elaborate description.

   -  Protocol authentication within the core

   The network infrastructure must support mechanisms for authentication
   of the control-plane messages.  If an MPLS/GMPLS core is used, LDP
   sessions may be authenticated with TCP MD5.  In addition, IGP and BGP
   authentication should be considered.  For a core providing various
   IP, VPN, or transport services, PE-to-PE authentication may also be
   performed via IPsec.  See the above discussion of protocol security
   services: authentication, integrity (with replay detection), and
   confidentiality.  Protocols need to provide a complete set of
   security services from which the SP can choose.  Also, the important
   but often more difficult part is key management.  Considerations,
   guidelines, and strategies regarding key management are discussed in
   [RFC3562], [RFC4107], [RFC4808].

   With today's processors, applying cryptographic authentication to the
   control plane may not increase the cost of deployment for providers
   significantly, and will help to improve the security of the core.  If
   the core is dedicated to MPLS/GMPLS enabled services without any
   interconnects to third parties, then this may reduce the requirement
   for authentication of the core control plane.

   -  Infrastructure Hiding

   Here we discuss means to hide the provider's infrastructure nodes.
   An MPLS/GMPLS provider may make its infrastructure routers (P and PE)
   unreachable from outside users and unauthorized internal users.  For
   example, separate address space may be used for the infrastructure
   loopbacks.

   Normal TTL propagation may be altered to make the backbone look like
   one hop from the outside, but caution needs to be taken for loop
   prevention.  This prevents the backbone addresses from being exposed
   through trace route; however, this must also be assessed against
   operational requirements for end-to-end fault tracing.

   An Internet backbone core may be re-engineered to make Internet
   routing an edge function, for example, by using MPLS label switching
   for all traffic within the core and possibly making the Internet a
   VPN within the PPVPN core itself.  This helps to detach Internet
   access from PPVPN services.

   Separating control-plane, data-plane, and management-plane
   functionality in hardware and software may be implemented on the PE



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   devices to improve security.  This may help to limit the problems
   when attacked in one particular area, and may allow each plane to
   implement additional security measures separately.

   PEs are often more vulnerable to attack than P routers, because PEs
   cannot be made unreachable from outside users by their very nature.
   Access to core trunk resources can be controlled on a per-user basis
   by using of inbound rate limiting or traffic shaping; this can be
   further enhanced on a per-class-of-service basis (see Section 8.2.3)

   In the PE, using separate routing processes for different services,
   for example, Internet and PPVPN service, may help to improve the
   PPVPN security and better protect VPN customers.  Furthermore, if
   resources, such as CPU and memory, can be further separated based on
   applications, or even individual VPNs, it may help to provide
   improved security and reliability to individual VPN customers.

7.1.2.  Control-Plane Protection with RSVP-TE

   -  General RSVP Security Tools

   Isolation of the trusted domain is an important security mechanism
   for RSVP, to ensure that an untrusted element cannot access a router
   of the trusted domain.  However, ASBR-ASBR communication for inter-AS
   LSPs needs to be secured specifically.  Isolation mechanisms might
   also be bypassed by an IPv4 Router Alert or IPv6 using Next Header 0
   packets.  A solution could consist of disabling the processing of IP
   options.  This drops or ignores all IP packets with IPv4 options,
   including the router alert option used by RSVP; however, this may
   have an impact on other protocols using IPv4 options.  An alternative
   is to configure access-lists on all incoming interfaces dropping IPv4
   protocol or IPv6 next header 46 (RSVP).

   RSVP security can be strengthened by deactivating RSVP on interfaces
   with neighbors who are not authorized to use RSVP, to protect against
   adjacent CE-PE attacks.  However, this does not really protect
   against DoS attacks or attacks on non-adjacent routers.  It has been
   demonstrated that substantial CPU resources are consumed simply by
   processing received RSVP packets, even if the RSVP process is
   deactivated for the specific interface on which the RSVP packets are
   received.

   RSVP neighbor filtering at the protocol level, to restrict the set of
   neighbors that can send RSVP messages to a given router, protects
   against non-adjacent attacks.  However, this does not protect against
   DoS attacks and does not effectively protect against spoofing of the
   source address of RSVP packets, if the filter relies on the
   neighbor's address within the RSVP message.



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   RSVP neighbor filtering at the data-plane level, with an access list
   to accept IP packets with port 46 only for specific neighbors,
   requires Router Alert mode to be deactivated and does not protect
   against spoofing.

   Another valuable tool is RSVP message pacing, to limit the number of
   RSVP messages sent to a given neighbor during a given period.  This
   allows blocking DoS attack propagation.

   -  Another approach is to limit the impact of an attack on control-
      plane resources.

   To ensure continued effective operation of the MPLS router even in
   the case of an attack that bypasses packet filtering mechanisms such
   as Access Control Lists in the data plane, it is important that
   routers have some mechanisms to limit the impact of the attack.
   There should be a mechanism to rate limit the amount of control-plane
   traffic addressed to the router, per interface.  This should be
   configurable on a per-protocol basis, (and, ideally, on a per-sender
   basis) to avoid letting an attacked protocol or a given sender block
   all communications.  This requires the ability to filter and limit
   the rate of incoming messages of particular protocols, such as RSVP
   (filtering at the IP protocol level), and particular senders.  In
   addition, there should be a mechanism to limit CPU and memory
   capacity allocated to RSVP, so as to protect other control-plane
   elements.  To limit memory allocation, it will probably be necessary
   to limit the number of LSPs that can be set up.

   -  Authentication for RSVP messages

   RSVP message authentication is described in RFC 2747 [RFC2747] and
   RFC 3097 [RFC3097].  It is one of the most powerful tools for
   protection against RSVP-based attacks.  It applies cryptographic
   authentication to RSVP messages based on a secure message hash using
   a key shared by RSVP neighbors.  This protects against LSP creation
   attacks, at the expense of consuming significant CPU resources for
   digest computation.  In addition, if the neighboring RSVP speaker is
   compromised, it could be used to launch attacks using authenticated
   RSVP messages.  These methods, and certain other aspects of RSVP
   security, are explained in detail in RFC 4230 [RFC4230].  Key
   management must be implemented.  Logging and auditing as well as
   multiple layers of cryptographic protection can help here.  IPsec can
   also be used in some cases (see [RFC4230]).

   One challenge using RSVP message authentication arises in many cases
   where non-RSVP nodes are present in the network.  In such cases, the
   RSVP neighbor may not be known up front, thus neighbor-based keying
   approaches fail, unless the same key is used everywhere, which is not



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   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.




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   Rate limiting may be applied to the user interface/logical interfaces
   as a defense against DDoS bandwidth attack.  This is helpful when the
   PE device is supporting both multiple services, especially VPN and
   Internet Services, on the same physical interfaces through different
   logical interfaces.

7.2.1.  Link Authentication

   Authentication can be used to validate site access to the network via
   fixed or logical connections, e.g., L2TP or IPsec, respectively.  If
   the user wishes to hold the authentication credentials for access,
   then provider solutions require the flexibility for either direct
   authentication by the PE itself or interaction with a customer
   authentication server.  Mechanisms are required in the latter case to
   ensure that the interaction between the PE and the customer
   authentication server is appropriately secured.

7.2.2.  Access Routing Control

   Choice of routing protocols, e.g., RIP, OSPF, or BGP, may be used to
   provide control access between a CE and a PE.  Per-neighbor and per-
   VPN routing policies may be established to enhance security and
   reduce the impact of a malicious or non-malicious attack on the PE;
   the following mechanisms, in particular, should be considered:

   -  Limiting the number of prefixes that may be advertised on a per-
      access basis into the PE.  Appropriate action may be taken should
      a limit be exceeded, e.g., the PE shutting down the peer session
      to the CE

   -  Applying route dampening at the PE on received routing updates

   -  Definition of a per-VPN prefix limit after which additional
      prefixes will not be added to the VPN routing table.

   In the case of inter-provider connection, access protection, link
   authentication, and routing policies as described above may be
   applied.  Both inbound and outbound firewall or filtering mechanisms
   between ASes may be applied.  Proper security procedures must be
   implemented in inter-provider interconnection to protect the
   providers' network infrastructure and their customers.  This may be
   custom designed for each inter-provider peering connection, and must
   be agreed upon by both providers.








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7.2.3.  Access QoS

   MPLS/GMPLS providers offering QoS-enabled services require mechanisms
   to ensure that individual accesses are validated against their
   subscribed QoS profile and as such gain access to core resources that
   match their service profile.  Mechanisms such as per-class-of-service
   rate limiting or traffic shaping on ingress to the MPLS/GMPLS core
   are two options for providing this level of control.  Such mechanisms
   may require the per-class-of-service profile to be enforced either by
   marking, remarking, or discarding of traffic outside of the profile.

7.2.4.  Customer Service Monitoring Tools

   End users needing specific statistics on the core, e.g., routing
   table, interface status, or QoS statistics, place requirements on
   mechanisms at the PE both to validate the incoming user and limit the
   views available to that particular user.  Mechanisms should also be
   considered to ensure that such access cannot be used as means to
   construct a DoS attack (either maliciously or accidentally) on the PE
   itself.  This could be accomplished either through separation of
   these resources within the PE itself or via the capability to rate
   limiting, which is performed on the basis of each physical interface
   or each logical connection.

7.3.  General User Requirements for MPLS/GMPLS Providers

   MPLS/GMPLS providers must support end users' security requirements.
   Depending on the technologies used, these requirements may include:

   -  User control plane separation through routing isolation when
      applicable, for example, in the case of MPLS VPNs.

   -  Protection against intrusion, DoS attacks, and spoofing

   -  Access Authentication

   -  Techniques highlighted throughout this document that identify
      methodologies for the protection of resources and the MPLS/GMPLS
      infrastructure.

   Hardware or software errors in equipment leading to breaches in
   security are not within the scope of this document.

8.  Inter-Provider Security Requirements

   This section discusses security capabilities that are important at
   the MPLS/GMPLS inter-provider connections and at devices (including
   ASBR routers) supporting these connections.  The security



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   capabilities stated in this section should be considered as
   complementary to security considerations addressed in individual
   protocol specifications or security frameworks.

   Security vulnerabilities and exposures may be propagated across
   multiple networks because of security vulnerabilities arising in one
   peer's network.  Threats to security originate from accidental,
   administrative, and intentional sources.  Intentional threats include
   events such as spoofing and denial-of-service (DoS) attacks.

   The level and nature of threats, as well as security and availability
   requirements, may vary over time and from network to network.  This
   section, therefore, discusses capabilities that need to be available
   in equipment deployed for support of the MPLS InterCarrier
   Interconnect (MPLS-ICI).  Whether any particular capability is used
   in any one specific instance of the ICI is up to the service
   providers managing the PE equipment offering or using the ICI
   services.

8.1.  Control-Plane Protection

   This section discusses capabilities for control-plane protection,
   including protection of routing, signaling, and OAM capabilities.

8.1.1.  Authentication of Signaling Sessions

   Authentication may be needed for signaling sessions (i.e., BGP, LDP,
   and RSVP-TE) and routing sessions (e.g., BGP), as well as OAM
   sessions across domain boundaries.  Equipment must be able to support
   the exchange of all protocol messages over IPsec ESP, with NULL
   encryption and authentication, between the peering ASBRs.  Support
   for message authentication for LDP, BGP, and RSVP-TE authentication
   must also be provided.  Manual keying of IPsec should not be used.
   IKEv2 with pre-shared secrets or public key methods should be used.
   Replay detection should be used.

   Mechanisms to authenticate and validate a dynamic setup request must
   be available.  For instance, if dynamic signaling of a TE-LSP or PW
   is crossing a domain boundary, there must be a way to detect whether
   the LSP source is who it claims to be and that it is allowed to
   connect to the destination.

   Message authentication support for all TCP-based protocols within the
   scope of the MPLS-ICI (i.e., LDP signaling and BGP routing) and
   Message authentication with the RSVP-TE Integrity Object must be
   provided to interoperate with current practices.  Equipment should be
   able to support the exchange of all signaling and routing (LDP, RSVP-
   TE, and BGP) protocol messages over a single IPsec association pair



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   in tunnel or transport mode with authentication but with NULL
   encryption, between the peering ASBRs.  IPsec, if supported, must be
   supported with HMAC-SHA-1 and alternatively with HMAC-SHA-2 and
   optionally SHA-1.  It is expected that authentication algorithms will
   evolve over time and support can be updated as needed.

   OAM operations across the MPLS-ICI could also be the source of
   security threats on the provider infrastructure as well as the
   service offered over the MPLS-ICI.  A large volume of OAM messages
   could overwhelm the processing capabilities of an ASBR if the ASBR is
   not properly protected.  Maliciously generated OAM messages could
   also be used to bring down an otherwise healthy service (e.g., MPLS
   Pseudowire), and therefore affect service security.  LSP ping does
   not support authentication today, and that support should be a
   subject for future consideration.  Bidirectional Forwarding Detection
   (BFD), however, does have support for carrying an authentication
   object.  It also supports Time-To-Live (TTL) processing as an anti-
   replay measure.  Implementations conformant with this MPLS-ICI should
   support BFD authentication and must support the procedures for TTL
   processing.

8.1.2.  Protection Against DoS Attacks in the Control Plane

   Implementations must have the ability to prevent signaling and
   routing DoS attacks on the control plane per interface and provider.
   Such prevention may be provided by rate limiting signaling and
   routing messages that can be sent by a peer provider according to a
   traffic profile and by guarding against malformed packets.

   Equipment must provide the ability to filter signaling, routing, and
   OAM packets destined for the device, and must provide the ability to
   rate limit such packets.  Packet filters should be capable of being
   separately applied per interface, and should have minimal or no
   performance impact.  For example, this allows an operator to filter
   or rate limit signaling, routing, and OAM messages that can be sent
   by a peer provider and limit such traffic to a given profile.

   During a control-plane DoS attack against an ASBR, the router should
   guarantee sufficient resources to allow network operators to execute
   network management commands to take corrective action, such as
   turning on additional filters or disconnecting an interface under
   attack.  DoS attacks on the control plane should not adversely affect
   data-plane performance.

   Equipment running BGP must support the ability to limit the number of
   BGP routes received from any particular peer.  Furthermore, in the
   case of IPVPN, a router must be able to limit the number of routes




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   learned from a BGP peer per IPVPN.  In the case that a device has
   multiple BGP peers, it should be possible for the limit to vary
   between peers.

8.1.3.  Protection against Malformed Packets

   Equipment should be robust in the presence of malformed protocol
   packets.  For example, malformed routing, signaling, and OAM packets
   should be treated in accordance with the relevant protocol
   specification.

8.1.4.  Ability to Enable/Disable Specific Protocols

   Equipment must have the ability to drop any signaling or routing
   protocol messages when these messages are to be processed by the ASBR
   but the corresponding protocol is not enabled on that interface.

   Equipment must allow an administrator to enable or disable a protocol
   (by default, the protocol is disabled unless administratively
   enabled) on an interface basis.

   Equipment must be able to drop any signaling or routing protocol
   messages when these messages are to be processed by the ASBR but the
   corresponding protocol is not enabled on that interface.  This
   dropping should not adversely affect data-plane or control-plane
   performance.

8.1.5.  Protection against Incorrect Cross Connection

   The capability to detect and locate faults in an LSP cross-connect
   must be provided.  Such faults may cause security violations as they
   result in directing traffic to the wrong destinations.  This
   capability may rely on OAM functions.  Equipment must support MPLS
   LSP ping [RFC4379].  This may be used to verify end-to-end
   connectivity for the LSP (e.g., PW, TE Tunnel, VPN LSP, etc.), and to
   verify PE-to-PE connectivity for IPVPN services.

   When routing information is advertised from one domain to the other,
   operators must be able to guard against situations that result in
   traffic hijacking, black-holing, resource stealing (e.g., number of
   routes), etc.  For instance, in the IPVPN case, an operator must be
   able to block routes based on associated route target attributes.  In
   addition, mechanisms to defend against routing protocol attack must
   exist to verify whether a route advertised by a peer for a given VPN
   is actually a valid route and whether the VPN has a site attached to
   or reachable through that domain.





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   Equipment (ASBRs and Route Reflectors (RRs)) supporting operation of
   BGP must be able to restrict which route target attributes are sent
   to and accepted from a BGP peer across an ICI.  Equipment (ASBRs,
   RRs) should also be able to inform the peer regarding which route
   target attributes it will accept from a peer, because sending an
   incorrect route target can result in an incorrect cross-connection of
   VPNs.  Also, sending inappropriate route targets to a peer may
   disclose confidential information.  This is another example of
   defense against routing protocol attacks.

8.1.6.  Protection against Spoofed Updates and Route Advertisements

   Equipment must support route filtering of routes received via a BGP
   peer session by applying policies that include one or more of the
   following: AS path, BGP next hop, standard community, or extended
   community.

8.1.7.  Protection of Confidential Information

   The ability to identify and block messages with confidential
   information from leaving the trusted domain that can reveal
   confidential information about network operation (e.g., performance
   OAM messages or LSP ping messages) is required.  SPs must have the
   flexibility to handle these messages at the ASBR.

   Equipment should be able to identify and restrict where it sends
   messages that can reveal confidential information about network
   operation (e.g., performance OAM messages, LSP Traceroute messages).
   Service Providers must have the flexibility to handle these messages
   at the ASBR.  For example, equipment supporting LSP Traceroute may
   limit to which addresses replies can be sent.  Note that this
   capability should be used with care.  For example, if an SP chooses
   to prohibit the exchange of LSP ping messages at the ICI, it may make
   it more difficult to debug incorrect cross-connection of LSPs or
   other problems.

   An SP may decide to progress these messages if they arrive from a
   trusted provider and are targeted to specific, agreed-on addresses.
   Another provider may decide to traffic police, reject, or apply other
   policies to these messages.  Solutions must enable providers to
   control the information that is relayed to another provider about the
   path that an LSP takes.  For example, when using the RSVP-TE record
   route object or LSP ping / trace, a provider must be able to control
   the information contained in corresponding messages when sent to
   another provider.






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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.





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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.





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9.1.  MPLS and GMPLS Specific Security Threats

9.1.1.  Control-Plane Attacks

   Types of attacks on the control plane:

   -  Unauthorized LSP creation

   -  LSP message interception

   Attacks against RSVP-TE: DoS attacks that set up unauthorized LSP
   and/or LSP messages.

   Attacks against LDP: DoS attack with storms of LDP Hello messages or
   LDP TCP SYN messages.

   Attacks may be launched from external or internal sources, or through
   an SP's management systems.

   Attacks may be targeted at the SP's routing protocols or
   infrastructure elements.

   In general, control protocols may be attacked by:

   -  MPLS signaling (LDP, RSVP-TE)

   -  PCE signaling

   -  IPsec signaling (IKE and IKEv2)

   -  ICMP and ICMPv6

   -  L2TP

   -  BGP-based membership discovery

   -  Database-based membership discovery (e.g., RADIUS)

   -  OAM and diagnostic protocols such as LSP ping and LMP

   -  Other protocols that may be important to the control
      infrastructure, e.g., DNS, LMP, NTP, SNMP, and GRE









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9.1.2.  Data-Plane Attacks

   - Unauthorized observation of data traffic

   - Data-traffic modification

   - Spoofing and replay

   - Unauthorized deletion

   - Unauthorized traffic-pattern analysis

   - Denial of Service

9.2.  Defense Techniques

   1)  Authentication:

      - Bidirectional authentication

      - Key management

      - Management system authentication

      - Peer-to-peer authentication

   2)  Cryptographic techniques

   3)  Use of IPsec in MPLS/GMPLS networks

   4)  Encryption for device configuration and management

   5)  Cryptographic techniques for MPLS pseudowires

   6)  End-to-End versus Hop-by-Hop protection (CE-CE, PE-PE, PE-CE)

   7)  Access control techniques

         - Filtering

         - Firewalls

         - Access Control to management interfaces

   8)  Infrastructure isolation

   9)  Use of aggregated infrastructure




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   10) Quality control processes

   11) Testable MPLS/GMPLS service

   12) End-to-end connectivity verification

   13) Hop-by-hop resource configuration verification and discovery

9.3.  Service Provider MPLS and GMPLS Best-Practice Outlines

9.3.1.  SP Infrastructure Protection

   1) General control-plane protection

      -  Filtering out infrastructure source addresses at edges

      -  Protocol authentication within the core

      -  Infrastructure hiding (e.g., disable TTL propagation)

   2) RSVP control-plane protection

      -  RSVP security tools

      -  Isolation of the trusted domain

      -  Deactivating RSVP on interfaces with neighbors who are not
         authorized to use RSVP

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

      -  Authentication for RSVP messages

      -  RSVP message pacing

   3) LDP control-plane protection (similar techniques as for RSVP)

   4) Data-plane protection

      -  User access link protection

      -  Link authentication

      -  Access routing control (e.g., prefix limits, route dampening,
         routing table limits (such as VRF limits)

      -  Access QoS control



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      -  Customer service monitoring tools

      -  Use of LSP ping (with its own control-plane security) to verify
         end-to-end connectivity of MPLS LSPs

      -  LMP (with its own security) to verify hop-by-hop connectivity.

9.3.2.  Inter-Provider Security

   Inter-provider connections are high security risk areas.  Similar
   techniques and procedures as described for SP's general core
   protection are listed below for inter-provider connections.

   1) Control-plane protection at inter-provider connections

      -  Authentication of signaling sessions

      -  Protection against DoS attacks in the control plane

      -  Protection against malformed packets

      -  Ability to enable/disable specific protocols

      -  Protection against incorrect cross connection

      -  Protection against spoofed updates and route advertisements

      -  Protection of confidential information

      -  Protection against an over-provisioned number of RSVP-TE LSPs
         and bandwidth reservation

   2) Data-plane protection at the inter-provider connections

      -  Protection against DoS in the data plane

      -  Protection against label spoofing

   For MPLS VPN interconnections [RFC4364], in practice, inter-AS option
   a), VRF-to-VRF connections at the AS (Autonomous System) border, is
   commonly used for inter-provider connections.  Option c), Multi-hop
   EBGP redistribution of labeled VPN-IPv4 routes between source and
   destination ASes with EBGP redistribution of labeled IPv4 routes from
   AS to a neighboring AS, on the other hand, is not normally used for
   inter-provider connections due to higher security risks.  For more
   details, please see [RFC4111].





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10.  Security Considerations

   Security considerations constitute the sole subject of this memo and
   hence are discussed throughout.  Here we recap what has been
   presented and explain at a high level the role of each type of
   consideration in an overall secure MPLS/GMPLS system.

   The document describes a number of potential security threats.  Some
   of these threats have already been observed occurring in running
   networks; others are largely hypothetical at this time.

   DoS attacks and intrusion attacks from the Internet against an SPs'
   infrastructure have been seen.  DoS "attacks" (typically not
   malicious) have also been seen in which CE equipment overwhelms PE
   equipment with high quantities or rates of packet traffic or routing
   information.  Operational or provisioning errors are cited by SPs as
   one of their prime concerns.

   The document describes a variety of defensive techniques that may be
   used to counter the suspected threats.  All of the techniques
   presented involve mature and widely implemented technologies that are
   practical to implement.

   The document describes the importance of detecting, monitoring, and
   reporting attacks, both successful and unsuccessful.  These
   activities are essential for "understanding one's enemy", mobilizing
   new defenses, and obtaining metrics about how secure the MPLS/GMPLS
   network is.  As such, they are vital components of any complete PPVPN
   security system.

   The document evaluates MPLS/GMPLS security requirements from a
   customer's perspective as well as from a service provider's
   perspective.  These sections re-evaluate the identified threats from
   the perspectives of the various stakeholders and are meant to assist
   equipment vendors and service providers, who must ultimately decide
   what threats to protect against in any given configuration or service
   offering.

11.  References

11.1.  Normative References

   [RFC2747]         Baker, F., Lindell, B., and M. Talwar, "RSVP
                     Cryptographic Authentication", RFC 2747, January
                     2000.






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   [RFC3031]         Rosen, E., Viswanathan, A., and R. Callon,
                     "Multiprotocol Label Switching Architecture", RFC
                     3031, January 2001.

   [RFC3097]         Braden, R. and L. Zhang, "RSVP Cryptographic
                     Authentication -- Updated Message Type Value", RFC
                     3097, April 2001.

   [RFC3209]         Awduche, D., Berger, L., Gan, D., Li, T.,
                     Srinivasan, V., and G. Swallow, "RSVP-TE:
                     Extensions to RSVP for LSP Tunnels", RFC 3209,
                     December 2001.

   [RFC3945]         Mannie, E., Ed., "Generalized Multi-Protocol Label
                     Switching (GMPLS) Architecture", RFC 3945, October
                     2004.

   [RFC4106]         Viega, J. and D. McGrew, "The Use of Galois/Counter
                     Mode (GCM) in IPsec Encapsulating Security Payload
                     (ESP)", RFC 4106, June 2005.

   [RFC4301]         Kent, S. and K. Seo, "Security Architecture for the
                     Internet Protocol", RFC 4301, December 2005.

   [RFC4302]         Kent, S., "IP Authentication Header", RFC 4302,
                     December 2005.

   [RFC4306]         Kaufman, C., Ed., "Internet Key Exchange (IKEv2)
                     Protocol", RFC 4306, December 2005.

   [RFC4309]         Housley, R., "Using Advanced Encryption Standard
                     (AES) CCM Mode with IPsec Encapsulating Security
                     Payload (ESP)", RFC 4309, December 2005.

   [RFC4364]         Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual
                     Private Networks (VPNs)", RFC 4364, February 2006.

   [RFC4379]         Kompella, K. and G. Swallow, "Detecting Multi-
                     Protocol Label Switched (MPLS) Data Plane
                     Failures", RFC 4379, February 2006.

   [RFC4447]         Martini, L., Ed., Rosen, E., El-Aawar, N., Smith,
                     T., and G. Heron, "Pseudowire Setup and Maintenance
                     Using the Label Distribution Protocol (LDP)", RFC
                     4447, April 2006.






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   [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.




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   [STD8]            Postel, J. and J. Reynolds, "Telnet Protocol
                     Specification", STD 8, RFC 854, May 1983.

                     Postel, J. and J. Reynolds, "Telnet Option
                     Specifications", STD 8, RFC 855, May 1983.

11.2.  Informative References

   [OIF-SMI-01.0]    Renee Esposito, "Security for Management Interfaces
                     to Network Elements", Optical Internetworking
                     Forum, Sept. 2003.

   [OIF-SMI-02.1]    Renee Esposito, "Addendum to the Security for
                     Management Interfaces to Network Elements", Optical
                     Internetworking Forum, March 2006.

   [RFC2104]         Krawczyk, H., Bellare, M., and R. Canetti, "HMAC:
                     Keyed-Hashing for Message Authentication", RFC
                     2104, February 1997.

   [RFC2411]         Thayer, R., Doraswamy, N., and R. Glenn, "IP
                     Security Document Roadmap", RFC 2411, November
                     1998.

   [RFC3174]         Eastlake 3rd, D. and P. Jones, "US Secure Hash
                     Algorithm 1 (SHA1)", RFC 3174, September 2001.

   [RFC3562]         Leech, M., "Key Management Considerations for the
                     TCP MD5 Signature Option", RFC 3562, July 2003.

   [RFC3631]         Bellovin, S., Ed., Schiller, J., Ed., and C.
                     Kaufman, Ed., "Security Mechanisms for the
                     Internet", RFC 3631, December 2003.

   [RFC3704]         Baker, F. and P. Savola, "Ingress Filtering for
                     Multihomed Networks", BCP 84, RFC 3704, March 2004.

   [RFC3985]         Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire
                     Emulation Edge-to-Edge (PWE3) Architecture", RFC
                     3985, March 2005.

   [RFC4107]         Bellovin, S. and R. Housley, "Guidelines for
                     Cryptographic Key Management", BCP 107, RFC 4107,
                     June 2005.

   [RFC4110]         Callon, R. and M. Suzuki, "A Framework for Layer 3
                     Provider-Provisioned Virtual Private Networks
                     (PPVPNs)", RFC 4110, July 2005.



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   [RFC4111]         Fang, L., Ed., "Security Framework for Provider-
                     Provisioned Virtual Private Networks (PPVPNs)", RFC
                     4111, July 2005.

   [RFC4230]         Tschofenig, H. and R. Graveman, "RSVP Security
                     Properties", RFC 4230, December 2005.

   [RFC4308]         Hoffman, P., "Cryptographic Suites for IPsec", RFC
                     4308, December 2005.

   [RFC4377]         Nadeau, T., Morrow, M., Swallow, G., Allan, D., and
                     S. Matsushima, "Operations and Management (OAM)
                     Requirements for Multi-Protocol Label Switched
                     (MPLS) Networks", RFC 4377, February 2006.

   [RFC4378]         Allan, D., Ed., and T. Nadeau, Ed., "A Framework
                     for Multi-Protocol Label Switching (MPLS)
                     Operations and Management (OAM)", RFC 4378,
                     February 2006.

   [RFC4593]         Barbir, A., Murphy, S., and Y. Yang, "Generic
                     Threats to Routing Protocols", RFC 4593, October
                     2006.

   [RFC4778]         Kaeo, M., "Operational Security Current Practices
                     in Internet Service Provider Environments", RFC
                     4778, January 2007.

   [RFC4808]         Bellovin, S., "Key Change Strategies for TCP-MD5",
                     RFC 4808, March 2007.

   [RFC4864]         Van de Velde, G., Hain, T., Droms, R., Carpenter,
                     B., and E. Klein, "Local Network Protection for
                     IPv6", RFC 4864, May 2007.

   [RFC4869]         Law, L. and J. Solinas, "Suite B Cryptographic
                     Suites for IPsec", RFC 4869, May 2007.

   [RFC5254]         Bitar, N., Ed., Bocci, M., Ed., and L. Martini,
                     Ed., "Requirements for Multi-Segment Pseudowire
                     Emulation Edge-to-Edge (PWE3)", RFC 5254, October
                     2008.

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






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   [OIF-Sec-Mag]     R. Esposito, R. Graveman, and B. Hazzard, "Security
                     for Management Interfaces to Network Elements,"
                     OIF-SMI-01.0, September 2003.

   [BACKBONE-ATTKS]  Savola, P., "Backbone Infrastructure Attacks and
                     Protections", Work in Progress, January 2007.

   [OPSEC-FILTER]    Morrow, C., Jones, G., and V. Manral, "Filtering
                     and Rate Limiting Capabilities for IP Network
                     Infrastructure", Work in Progress, July 2007.

   [IPSECME-ROADMAP] Frankel, S. and S. Krishnan, "IP Security (IPsec)
                     and Internet Key Exchange (IKE) Document Roadmap",
                     Work in Progress, May 2010.

   [OPSEC-EFFORTS]   Lonvick, C. and D. Spak, "Security Best Practices
                     Efforts and Documents", Work in Progress, May 2010.

   [RSVP-key]        Behringer, M. and F. Le Faucheur, "Applicability of
                     Keying Methods for RSVP Security", Work in
                     Progress, June 2009.

12.  Acknowledgements

   The authors and contributors would also like to acknowledge the
   helpful comments and suggestions from Sam Hartman, Dimitri
   Papadimitriou, Kannan Varadhan, Stephen Farrell, Mircea Pisica, Scott
   Brim in particular for his comments and discussion through GEN-ART
   review,as well as Suresh Krishnan for his GEN-ART review and
   comments.  The authors would like to thank Sandra Murphy and Tim Polk
   for their comments and help through Security AD review, thank Pekka
   Savola for his comments through ops-dir review, and Amanda Baber for
   her IANA review.

   This document has used relevant content from RFC 4111 "Security
   Framework of Provider Provisioned VPN for Provider-Provisioned
   Virtual Private Networks (PPVPNs)" [RFC4111].  We acknowledge the
   authors of RFC 4111 for the valuable information and text.

   Authors:

   Luyuan Fang, Ed., Cisco Systems, Inc.
   Michael Behringer, Cisco Systems, Inc.
   Ross Callon, Juniper Networks
   Richard Graveman, RFG Security, LLC
   J. L. Le Roux, France Telecom
   Raymond Zhang, British Telecom
   Paul Knight, Individual Contributor



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   Yaakov Stein, RAD Data Communications
   Nabil Bitar, Verizon
   Monique Morrow, Cisco Systems, Inc.
   Adrian Farrel, Old Dog Consulting

   As a design team member for the MPLS Security Framework, Jerry Ash
   also made significant contributions to this document.

13.  Contributors' Contact Information

   Michael Behringer
   Cisco Systems, Inc.
   Village d'Entreprises Green Side
   400, Avenue Roumanille, Batiment T 3
   06410 Biot, Sophia Antipolis
   FRANCE
   EMail: mbehring@cisco.com

   Ross Callon
   Juniper Networks
   10 Technology Park Drive
   Westford, MA 01886
   USA
   EMail: rcallon@juniper.net

   Richard Graveman
   RFG Security
   15 Park Avenue
   Morristown, NJ  07960
   EMail: rfg@acm.org

   Jean-Louis Le Roux
   France Telecom
   2, avenue Pierre-Marzin
   22307 Lannion Cedex
   FRANCE
   EMail: jeanlouis.leroux@francetelecom.com

   Raymond Zhang
   British Telecom
   BT Center
   81 Newgate Street
   London, EC1A 7AJ
   United Kingdom
   EMail: raymond.zhang@bt.com






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   Paul Knight
   39 N. Hancock St.
   Lexington, MA 02420
   EMail: paul.the.knight@gmail.com

   Yaakov (Jonathan) Stein
   RAD Data Communications
   24 Raoul Wallenberg St., Bldg C
   Tel Aviv  69719
   ISRAEL
   EMail: yaakov_s@rad.com

   Nabil Bitar
   Verizon
   40 Sylvan Road
   Waltham, MA 02145
   EMail: nabil.bitar@verizon.com

   Monique Morrow
   Glatt-com
   CH-8301 Glattzentrum
   Switzerland
   EMail: mmorrow@cisco.com

   Adrian Farrel
   Old Dog Consulting
   EMail: adrian@olddog.co.uk

Editor's Address

   Luyuan Fang (editor)
   Cisco Systems, Inc.
   300 Beaver Brook Road
   Boxborough, MA 01719
   USA
   EMail: lufang@cisco.com















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