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rfc:rfc6518

Internet Engineering Task Force (IETF) G. Lebovitz Request for Comments: 6518 M. Bhatia Category: Informational Alcatel-Lucent ISSN: 2070-1721 February 2012

       Keying and Authentication for Routing Protocols (KARP)
                         Design Guidelines

Abstract

 This document is one of a series concerned with defining a roadmap of
 protocol specification work for the use of modern cryptographic
 mechanisms and algorithms for message authentication in routing
 protocols.  In particular, it defines the framework for a key
 management protocol that may be used to create and manage session
 keys for message authentication and integrity.

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/rfc6518.

Lebovitz & Bhatia Informational [Page 1] RFC 6518 KARP Design Guidelines February 2012

Copyright Notice

 Copyright (c) 2012 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1. Introduction ....................................................3
    1.1. Conventions Used in This Document ..........................4
 2. Categorizing Routing Protocols ..................................5
    2.1. Category: Message Transaction Type .........................5
    2.2. Category: Peer versus Group Keying .........................6
 3. Consider the Future Existence of a Key Management Protocol ......6
    3.1. Consider Asymmetric Keys ...................................7
    3.2. Cryptographic Keys Life Cycle ..............................8
 4. Roadmap .........................................................9
    4.1. Work Phases on Any Particular Protocol .....................9
    4.2. Work Items per Routing Protocol ...........................11
 5. Routing Protocols in Categories ................................13
 6. Supporting Incremental Deployment ..............................16
 7. Denial-of-Service Attacks ......................................17
 8. Gap Analysis ...................................................18
 9. Security Considerations ........................................20
    9.1. Use Strong Keys ...........................................21
    9.2. Internal versus External Operation ........................22
    9.3. Unique versus Shared Keys .................................22
    9.4. Key Exchange Mechanism ....................................24
 10. Acknowledgments ...............................................26
 11. References ....................................................26
     11.1. Normative References ....................................26
     11.2. Informative References ..................................26

Lebovitz & Bhatia Informational [Page 2] RFC 6518 KARP Design Guidelines February 2012

1. Introduction

 In March 2006, the Internet Architecture Board (IAB) held a workshop
 on the topic of "Unwanted Internet Traffic".  The report from that
 workshop is documented in RFC 4948 [RFC4948].  Section 8.1 of that
 document states that "A simple risk analysis would suggest that an
 ideal attack target of minimal cost but maximal disruption is the
 core routing infrastructure".  Section 8.2 calls for "[t]ightening
 the security of the core routing infrastructure".  Four main steps
 were identified for that tightening:
 o  Increase the security mechanisms and practices for operating
    routers.
 o  Clean up the Internet Routing Registry [IRR] repository, and
    securing both the database and the access, so that it can be used
    for routing verifications.
 o  Create specifications for cryptographic validation of routing
    message content.
 o  Secure the routing protocols' packets on the wire.
 The first bullet is being addressed in the OPSEC working group.  The
 second bullet should be addressed through liaisons with those running
 the IRR's globally.  The third bullet is being addressed in the SIDR
 working group.
 This document addresses the last bullet, securing the packets on the
 wire of the routing protocol exchanges.  Thus, it is concerned with
 guidelines for describing issues and techniques for protecting the
 messages between directly communicating peers.  This may overlap
 with, but is strongly distinct from, protection designed to ensure
 that routing information is properly authorized relative to sources
 of this information.  Such authorizations are provided by other
 mechanisms and are outside the scope of this document and the work
 that relies on it.
 This document uses the terminology "on the wire" to talk about the
 information used by routing systems.  This term is widely used in
 RFCs, but is used in several different ways.  In this document, it is
 used to refer both to information exchanged between routing protocol
 instances and to underlying protocols that may also need to be
 protected in specific circumstances.  Other documents that will
 analyze individual protocols will need to indicate how they use the
 term "on the wire".

Lebovitz & Bhatia Informational [Page 3] RFC 6518 KARP Design Guidelines February 2012

 The term "routing transport" is used to refer to the layer that
 exchanges the routing protocols.  This can be TCP, UDP, or even
 direct link-level messaging in the case of some routing protocols.
 The term is used here to allow a referent for discussing both common
 and disparate issues that affect or interact with this dimension of
 the routing systems.  The term is used here to refer generally to the
 set of mechanisms and exchanges underneath the routing protocol,
 whatever that is in specific cases.
 Keying and Authentication for Routing Protocols (KARP) will focus on
 an abstraction for keying information that describes the interface
 between routing protocols, operators, and automated key management.
 Conceptually, when routing protocols send or receive messages, they
 will look up the key to use in this abstract key table.
 Conceptually, there will be an interface for a routing protocol to
 make requests of automated key management when it is being used; when
 keys become available, they will be made available in the key table.
 There is no requirement that this abstraction be used for
 implementation; the abstraction serves the needs of standardization
 and management.  Specifically, as part of the KARP work plan:
 1) KARP will design the key table abstraction, the interface between
    key management protocols and routing protocols, and possibly
    security protocols at other layers.
 2) For each routing protocol, KARP will define the mapping between
    how the protocol represents key material and the protocol-
    independent key table abstraction.  When routing protocols share a
    common mechanism for authentication, such as the TCP
    Authentication Option, the same mapping is likely to be reused
    between protocols.  An implementation may be able to move much of
    the keying logic into code related to this shared authentication
    primitive rather than code specific to routing protocols.
 3) When designing automated key management for both symmetric keys
    and group keys, we will only use the abstractions designed in
    point 1 above to communicate between automated key management and
    routing protocols.
 Readers must refer to [THTS-REQS] for a clear definition of the
 scope, goals, non-goals, and the audience for the design work being
 undertaken in the KARP WG.

1.1. Conventions Used in This Document

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC 2119 [RFC2119].

Lebovitz & Bhatia Informational [Page 4] RFC 6518 KARP Design Guidelines February 2012

2. Categorizing Routing Protocols

 This document places the routing protocols into two categories
 according to their requirements for authentication.  We hope these
 categories will allow design teams to focus on security mechanisms
 for a given category.  Further, we hope that each protocol in the
 group will be able to reuse the authentication mechanism.  It is also
 hoped that, down the road, we can create one Key Management Protocol
 (KMP) per category (if not for several categories), so that the work
 can be easily leveraged for use in the various routing protocol
 groupings.  KMPs are useful for allowing simple, automated updates of
 the traffic keys used in a base protocol.  KMPs replace the need for
 humans, or operational support systems (OSS) routines, to
 periodically replace keys on running systems.  It also removes the
 need for a chain of manual keys to be chosen or configured on such
 systems.  When configured properly, a KMP will enforce the key
 freshness policy among peers by keeping track of the key's lifetime
 and negotiating a new key at the defined interval.

2.1. Category: Message Transaction Type

 The first category defines three types of messaging transactions used
 on the wire by the base routing protocol.  They are as follows:
    One-to-One
       One peer router directly and intentionally delivers a route
       update specifically to one other peer router.  Examples are BGP
       [RFC4271]; LDP [RFC5036]; BFD [RFC5880]; and RSVP-TE [RFC3209],
       [RFC3473], [RFC4726], and [RFC5151].  Point-to-point modes of
       both IS-IS [RFC1195] and OSPF [RFC2328], when sent over both
       traditional point-to-point links and when using multi-access
       layers, may both also fall into this category.
    One-to-Many
       A router peers with multiple other routers on a single network
       segment -- i.e., on link local -- such that it creates and
       sends one route update message that is intended for multiple
       peers.  Examples would be OSPF and IS-IS in their broadcast,
       non-point-to-point mode and Routing Information Protocol (RIP)
       [RFC2453].
    Multicast
       Multicast protocols have unique security properties because
       they are inherently group-based protocols; thus, they have
       group keying requirements at the routing level where link-local

Lebovitz & Bhatia Informational [Page 5] RFC 6518 KARP Design Guidelines February 2012

       routing messages are multicasted.  Also, at least in the case
       of Protocol Independent Multicast - Sparse Mode (PIM-SM)
       [RFC4601], some messages are sent unicast to a given peer(s),
       as is the case with router-close-to-sender and the "Rendezvous
       Point".  Some work for application-layer message security has
       been done in the Multicast Security (MSEC) working group and
       may be helpful to review, but it is not directly applicable.
 These categories affect both the routing protocol view of the
 communication and the actual message transfer.  As a result, some
 message transaction types for a few routing protocols may be
 mixtures, for example, using broadcast where multicast might be
 expected or using unicast to deliver what looks to the routing
 protocol like broadcast or multicast.
 Protocol security analysis documents produced in the KARP working
 group need to pay attention both to the semantics of the
 communication and the techniques that are used for the message
 exchanges.

2.2. Category: Peer versus Group Keying

 The second category is the keying mechanism that will be used to
 distribute the session keys to the routing transports.  They are as
 follows:
 Peer Keying
    One router sends the keying messages only to one other router,
    such that a one-to-one, uniquely keyed security association (SA)
    is established between the two routers (e.g., BGP, BFD and LDP).
 Group Keying
    One router creates and distributes a single keying message to
    multiple peers.  In this case, a group SA will be established and
    used among multiple peers simultaneously.  Group keying exists for
    protocols like OSPF [RFC2328] and for multicast protocols like
    PIM-SM [RFC4601].

3. Consider the Future Existence of a Key Management Protocol

 When it comes time for the KARP WG to design a reusable model for a
 Key Management Protocol (KMP), [RFC4107] should be consulted.

Lebovitz & Bhatia Informational [Page 6] RFC 6518 KARP Design Guidelines February 2012

 When conducting the design work on a manually keyed version of a
 routing protocol's authentication mechanism, consideration must be
 made for the eventual use of a KMP.  In particular, design teams must
 consider what parameters would need to be handed to the routing
 protocols by a KMP.
 Examples of parameters that might need to be passed are as follows: a
 security association identifier (e.g., IPsec Security Parameter Index
 (SPI) or the TCP Authentication Option's (TCP-AO's) KeyID), a key
 lifetime (which may be represented in either bytes or seconds), the
 cryptographic algorithms being used, the keys themselves, and the
 directionality of the keys (i.e., receiving versus the sending keys).

3.1. Consider Asymmetric Keys

 The use of asymmetric keys can be a very powerful way to authenticate
 machine peers as used in routing protocol peer exchanges.  If
 generated on the machine, and never moved off the machine, these keys
 will not need to be changed if an administrator leaves the
 organization.  Since the keys are random, they are far less
 susceptible to off-line dictionary and guessing attacks.
 An easy and simple way to use asymmetric keys is to start by having
 the router generate a public/private key pair.  At the time of this
 writing, the recommended key size for algorithms based on integer
 factorization cryptography like RSA is 1024 bits and 2048 bits for
 extremely valuable keys like the root key pair used by a
 certification authority.  It is believed that a 1024-bit RSA key is
 equivalent in strength to 80-bit symmetric keys and 2048-bit RSA keys
 to 112-bit symmetric keys [RFC3766].  Elliptic Curve Cryptography
 (ECC) [RFC4492] appears to be secure with shorter keys than those
 needed by other asymmetric key algorithms.  National Institute of
 Standards and Technology (NIST) guidelines [NIST-800-57] state that
 ECC keys should be twice the length of equivalent strength symmetric
 key algorithms.  Thus, a 224-bit ECC key would roughly have the same
 strength as a 112-bit symmetric key.
 Many routers have the ability to be remotely managed using Secure
 Shell (SSH) Protocol [RFC4252] and [RFC4253].  As such, routers will
 also have the ability to generate and store an asymmetric key pair,
 because this is the common authentication method employed by SSH when
 an administrator connects to a router for management sessions.

Lebovitz & Bhatia Informational [Page 7] RFC 6518 KARP Design Guidelines February 2012

 Once an asymmetric key pair is generated, the KMP generating security
 association parameters and keys for routing protocol may use the
 machine's asymmetric keys for the authentication mechanism.  The form
 of the identity proof could be raw keys, the more easily
 administrable self-signed certificate format, or a PKI-issued
 [RFC5280] certificate credential.
 Regardless of which credential is standardized, the authentication
 mechanism can be as simple as a strong hash over a string of human-
 readable and transferable form of ASCII characters.  More complex,
 but also more secure, the identity proof could be verified through
 the use of a PKI system's revocation checking mechanism, (e.g.,
 Certificate Revocation List (CRL) or Online Certificate Status
 Protocol (OCSP) responder).  If the SHA-1 fingerprint is used, the
 solution could be as simple as loading a set of neighbor routers'
 peer ID strings into a table and listing the associated fingerprint
 string for each ID string.  In most organizations or peering points,
 this list will not be longer than a thousand or so routers, and often
 the list will be much shorter.  In other words, the entire list for a
 given organization's router ID and hash could be held in a router's
 configuration file, uploaded, downloaded, and moved about at will.
 Additionally, it doesn't matter who sees or gains access to these
 fingerprints, because they can be distributed publicly as it needn't
 be kept secret.

3.2. Cryptographic Keys Life Cycle

 Cryptographic keys should have a limited lifetime and may need to be
 changed when an operator who had access to them leaves.  Using a key
 chain, a set of keys derived from the same keying material and used
 one after the other, also does not help as one still has to change
 all the keys in the key chain when an operator having access to all
 those keys leaves the company.  Additionally, key chains will not
 help if the routing transport subsystem does not support rolling over
 to the new keys without bouncing the routing sessions and
 adjacencies.  So the first step is to fix the routing stack so that
 routing protocols can change keys without breaking or bouncing the
 adjacencies.
 An often cited reason for limiting the lifetime of a key is to
 minimize the damage from a compromised key.  It could be argued that
 it is likely a user will not discover an attacker has compromised the
 key if the attacker remains "passive"; thus, relatively frequent key
 changes will limit any potential damage from compromised keys.

Lebovitz & Bhatia Informational [Page 8] RFC 6518 KARP Design Guidelines February 2012

 Another threat against the long-lived key is that one of the systems
 storing the key, or one of the users entrusted with the key, will be
 subverted.  So, while there may not be cryptographic motivations of
 changing the keys, there could be system security motivations for
 rolling the key.
 Although manual key distribution methods are subject to human error
 and frailty, more frequent manual key changes might actually increase
 the risk of exposure, as it is during the time that the keys are
 being changed that they are likely to be disclosed.  In these cases,
 especially when very strong cryptography is employed, it may be more
 prudent to have fewer, well-controlled manual key distributions
 rather than more frequent, poorly controlled manual key
 distributions.  In general, where strong cryptography is employed,
 physical, procedural, and logical access protection considerations
 often have more impact on the key life than do algorithm and key size
 factors.
 For incremental deployments, we could start by associating life times
 with the send and the receive keys in the key chain for the long-
 lived keys.  This is an incremental approach that we could use until
 the cryptographic keying material for individual sessions is derived
 from the keying material stored in a database of long-lived
 cryptographic keys as described in [CRPT-TAB].  A key derivation
 function (KDF) and its inputs are also specified in the database of
 long-lived cryptographic keys; session-specific values based on the
 routing protocol are input to the KDF.  Protocol-specific key
 identifiers may be assigned to the cryptographic keying material for
 individual sessions if needed.
 The long-lived cryptographic keys used by the routing protocols can
 either be inserted manually in a database or make use of an automated
 key management protocol to do this.

4. Roadmap

4.1. Work Phases on Any Particular Protocol

 It is believed that improving security for any routing protocol will
 be a two-phase process.  The first phase would be to modify routing
 protocols to support modern cryptography algorithms and key agility.
 The second phase would be to design and move to an automated key
 management mechanism.  This is like a crawl, walk, and run process.
 In order for operators to accept these phases, we believe that the
 key management protocol should be clearly separated from the routing
 transport.  This would mean that the routing transport subsystem is
 oblivious to how the keys are derived, exchanged, and downloaded as
 long as there is something that it can use.  It is like having a

Lebovitz & Bhatia Informational [Page 9] RFC 6518 KARP Design Guidelines February 2012

 routing-protocol-configuration switch that requests the security
 module for the "KARP security parameters" so that it can refer to
 some module written, maintained, and operated by security experts and
 insert those parameters in the routing exchange.
 The desired end state for the KARP work contains several items.
 First, the people desiring to deploy securely authenticated and
 integrity validated packets between routing peers have the tools
 specified, implemented, and shipped in order to deploy.  These tools
 should be fairly simple to implement and not more complex than the
 security mechanisms to which the operators are already accustomed.
 (Examples of security mechanisms to which router operators are
 accustomed include: the use of asymmetric keys for authentication in
 SSH for router configuration, the use of pre-shared keys (PSKs) in
 TCP MD5 for BGP protection, the use of self-signed certificates for
 HTTP Secure (HTTPS) access to device Web-based user interfaces, the
 use of strongly constructed passwords and/or identity tokens for user
 identification when logging into routers and management systems.)
 While the tools that we intend to specify may not be able to stop a
 deployment from using "foobar" as an input key for every device
 across their entire routing domain, we intend to make a solid, modern
 security system that is not too much more difficult than that.  In
 other words, simplicity and deployability are keys to success.  The
 routing protocols will specify modern cryptographic algorithms and
 security mechanisms.  Routing peers will be able to employ unique,
 pair-wise keys per peering instance, with reasonable key lifetimes,
 and updating those keys on a regular basis will be operationally
 easy, causing no service interruption.
 Achieving the above described end state using manual keys may be
 pragmatic only in very small deployments.  However, manual keying in
 larger deployments will be too burdensome for operators.  Thus, the
 second goal is to support key life cycle management with a KMP.  We
 expect that both manual and automated key management will coexist in
 the real world.
 In accordance with the desired end state just described, we define
 two main work phases for each routing protocol:
 1.  Enhance the routing protocol's current authentication
     mechanism(s).  This work involves enhancing a routing protocol's
     current security mechanisms in order to achieve a consistent,
     modern level of security functionality within its existing key
     management framework.  It is understood and accepted that the
     existing key management frameworks are largely based on manual
     keys.  Since many operators have already built operational
     support systems (OSS) around these manual key implementations,
     there is some automation available for an operator to leverage in

Lebovitz & Bhatia Informational [Page 10] RFC 6518 KARP Design Guidelines February 2012

     that way, if the underlying mechanisms are themselves secure.  In
     this phase, we explicitly exclude embedding or creating a KMP.
     Refer to [THTS-REQS] for the list of the requirements for Phase 1
     work.
 2.  Develop an automated key management framework.  The second phase
     will focus on the development of an automated keying framework to
     facilitate unique pair-wise (group-wise, where applicable) keys
     per peering instance.  This involves the use of a KMP.  The use
     of automatic key management mechanisms offers a number of
     benefits over manual keying.  Most important, it provides fresh
     traffic keying material for each session, thus helping to prevent
     inter-connection replay attacks.  In an inter-connection replay
     attack, protocol packets from the earlier protocol session are
     replayed affecting the current execution of the protocol.  A KMP
     is also helpful because it negotiates unique, pair-wise, random
     keys, without administrator involvement.  It negotiates several
     SA parameters like algorithms, modes, and parameters required for
     the secure connection, thus providing interoperability between
     endpoints with disparate capabilities and configurations.  In
     addition it could also include negotiating the key lifetimes.
     The KMP can thus keep track of those lifetimes using counters and
     can negotiate new keys and parameters before they expire, again,
     without administrator interaction.  Additionally, in the event of
     a breach, changing the KMP key will immediately cause a rekey to
     occur for the traffic key, and those new traffic keys will be
     installed and used in the current connection.  In summary, a KMP
     provides a protected channel between the peers through which they
     can negotiate and pass important data required to exchange proof
     of identities, derive traffic keys, determine rekeying,
     synchronize their keying state, signal various keying events,
     notify with error messages, etc.

4.2. Work Items per Routing Protocol

 Each routing protocol will have a team (the Routing_Protocol-KARP
 team, e.g., the OSPF-KARP team) working on incrementally improving
 the security of a routing protocol.  These teams will have the
 following main work items:
 PHASE 1:
    Characterize the Routing Protocol
       Assess the routing protocol to see what authentication and
       integrity mechanisms it has today.  Does it need significant
       improvement to its existing mechanisms or not?  This will

Lebovitz & Bhatia Informational [Page 11] RFC 6518 KARP Design Guidelines February 2012

       include determining if modern, strong security algorithms and
       parameters are present and if the protocol supports key agility
       without bouncing adjacencies.
    Define Optimal State
       List the requirements for the routing protocol's session key
       usage and format to contain modern, strong security algorithms
       and mechanisms, per the Requirements document [THTS-REQS].  The
       goal here is to determine what is needed for the routing
       protocol to be used securely with at least manual key
       management.
    Gap Analysis
       Enumerate the requirements for this protocol to move from its
       current security state, the first bullet, to its optimal state,
       as listed just above.
    Transition and Deployment Considerations
       Document the operational transition plan for moving from the
       old to the new security mechanism.  Will adjacencies need to
       bounce?  What new elements/servers/services in the
       infrastructure will be required?  What is an example work flow
       that an operator will take?  The best possible case is if the
       adjacency does not break, but this may not always be possible.
    Define, Assign, Design
       Create a deliverables list of the design and specification
       work, with milestones.  Define owners.  Release one or more
       documents.
 PHASE 2:
    KMP Analysis
       Review requirements for KMPs.  Identify any nuances for this
       particular routing protocol's needs and its use cases for a
       KMP.  List the requirements that this routing protocol has for
       being able to be used in conjunction with a KMP.  Define the
       optimal state and check how easily it can be decoupled from the
       KMP.

Lebovitz & Bhatia Informational [Page 12] RFC 6518 KARP Design Guidelines February 2012

    Gap Analysis
       Enumerate the requirements for this protocol to move from its
       current security state to its optimal state, with respect to
       the key management.
    Define, Assign, Design
       Create a deliverables list of the design and specification
       work, with milestones.  Define owners.  Generate the design and
       document work for a KMP to be able to generate the routing
       protocol's session keys for the packets on the wire.  These
       will be the arguments passed in the API to the KMP in order to
       bootstrap the session keys for the routing protocol.
       There will also be a team formed to work on the base framework
       mechanisms for each of the main categories.

5. Routing Protocols in Categories

 This section groups the routing protocols into categories according
 to attributes set forth in the Categories' Section (Section 2).  Each
 group will have a design team tasked with improving the security of
 the routing protocol mechanisms and defining the KMP requirements for
 their group, then rolling both into a roadmap document upon which
 they will execute.
 BGP, LDP, PCEP, and MSDP
    These routing protocols fall into the category of the one-to-one
    peering messages and will use peer keying protocols.  Border
    Gateway Protocol (BGP) [RFC4271], Path Computation Element
    Communication Protocol (PCEP) [RFC5440], and Multicast Source
    Discovery Protocol (MSDP) [RFC3618] messages are transmitted over
    TCP, while Label Distribution Protocol (LDP) [RFC5036] uses both
    UDP and TCP.  A team will work on one mechanism to cover these TCP
    unicast protocols.  Much of the work on the routing protocol
    update for its existing authentication mechanism has already
    occurred in the TCPM working group, on the TCP-AO [RFC5925]
    document, as well as its cryptography-helper document, TCP-AO-
    CRYPTO [RFC5926].  However, TCP-AO cannot be used for discovery
    exchanges carried in LDP as those are carried over UDP.  A
    separate team might want to look at LDP.  Another exception is the
    mode where LDP is used directly on the LAN.  The work for this may
    go into the group keying category (along with OSPF) as mentioned
    below.

Lebovitz & Bhatia Informational [Page 13] RFC 6518 KARP Design Guidelines February 2012

 OSPF, IS-IS, and RIP
    The routing protocols that fall into the category group keying
    (with one-to-many peering) includes OSPF [RFC2328], IS-IS
    [RFC1195] and RIP [RFC2453].  Not surprisingly, all these routing
    protocols have two other things in common.  First, they are run on
    a combination of the OSI datalink Layer 2, and the OSI network
    Layer 3.  By this we mean that they have a component of how the
    routing protocol works, which is specified in Layer 2 as well as
    in Layer 3.  Second, they are all internal gateway protocols
    (IGPs).  The keying mechanisms will be much more complicated to
    define for these than for a one-to-one messaging protocol.
 BFD
    Because it is less of a routing protocol, per se, and more of a
    peer liveness detection mechanism, Bidirectional Forwarding
    Detection (BFD) [RFC5880] will have its own team.  BFD is also
    different from the other protocols covered here as it works on
    millisecond timers and would need separate considerations to
    mitigate the potential for Denial-of-Service (DoS) attacks.  It
    also raises interesting issues [RFC6039] with respect to the
    sequence number scheme that is generally deployed to protect
    against replay attacks as this space can roll over quite
    frequently because of the rate at which BFD packets are generated.
 RSVP and RSVP-TE
    The Resource reSerVation Protocol (RSVP) [RFC2205] allows hop-by-
    hop authentication of RSVP neighbors, as specified in [RFC2747].
    In this mode, an integrity object is attached to each RSVP message
    to transmit a keyed message digest.  This message digest allows
    the recipient to verify the identity of the RSVP node that sent
    the message and to validate the integrity of the message.  Through
    the inclusion of a sequence number in the scope of the digest, the
    digest also offers replay protection.
    [RFC2747] does not dictate how the key for the integrity operation
    is derived.  Currently, most implementations of RSVP use a
    statically configured key, on a per-interface or per-neighbor
    basis.
    RSVP relies on a per-peer authentication mechanism where each hop
    authenticates its neighbor using a shared key or a certificate.
    Trust in this model is transitive.  Each RSVP node trusts,
    explicitly, only its RSVP next-hop peers through the message
    digest contained in the INTEGRITY object [RFC2747].  The next-hop

Lebovitz & Bhatia Informational [Page 14] RFC 6518 KARP Design Guidelines February 2012

    RSVP speaker, in turn, trusts its own peers, and so on.  See also
    the document "RSVP Security Properties" [RFC4230] for more
    background.
    The keys used for protecting the RSVP messages can be group keys
    (for example, distributed via the Group Domain of Interpretation
    (GDOI) [RFC6407], as discussed in [GDOI-MAC]).
    The trust an RSVP node has with another RSVP node has an explicit
    and implicit component.  Explicitly, the node trusts the other
    node to maintain the integrity (and, optionally, the
    confidentiality) of RSVP messages depending on whether
    authentication or encryption (or both) are used.  This means that
    the message has not been altered or its contents seen by another,
    non-trusted node.  Implicitly, each node trusts the other node to
    maintain the level of protection specified within that security
    domain.  Note that in any group key management scheme, like GDOI,
    each node trusts all the other members of the group with regard to
    data origin authentication.
    RSVP-TE [RFC3209], [RFC3473], [RFC4726], and [RFC5151] is an
    extension of the RSVP protocol for traffic engineering.  It
    supports the reservation of resources across an IP network and is
    used for establishing MPLS label switch paths (LSPs), taking into
    consideration network constraint parameters such as available
    bandwidth and explicit hops.  RSVP-TE signaling is used to
    establish both intra- and inter-domain TE LSPs.
    When signaling an inter-domain RSVP-TE LSP, operators may make use
    of the security features already defined for RSVP-TE [RFC3209].
    This may require some coordination between domains to share keys
    ([RFC2747][RFC3097]), and care is required to ensure that the keys
    are changed sufficiently frequently.  Note that this may involve
    additional synchronization, should the domain border nodes be
    protected with Fast Reroute, since the merge point (MP) and point
    of local repair (PLR) should also share the key.
    For inter-domain signaling for MPLS-TE, the administrators of
    neighboring domains must satisfy themselves as to the existence of
    a suitable trust relationship between the domains.  In the absence
    of such a relationship, the administrators should decide not to
    deploy inter-domain signaling and should disable RSVP-TE on any
    inter-domain interfaces.
    KARP will currently be working only on RSVP-TE, as the native RSVP
    lies outside the scope of the WG charter.

Lebovitz & Bhatia Informational [Page 15] RFC 6518 KARP Design Guidelines February 2012

 PIM-SM and PIM-DM
    Finally, the multicast protocols Protocol Independent Multicast -
    Sparse Mode (PIM-SM) [RFC4601] and Protocol Independent Multicast
    - Dense Mode (PIM-DM) [RFC3973] will be grouped together.  PIM-SM
    multicasts routing information (Hello, Join/Prune, Assert) on a
    link-local basis, using a defined multicast address.  In addition,
    it specifies unicast communication for exchange of information
    (Register, Register-Stop) between the router closest to a group
    sender and the "Rendezvous Point".  The Rendezvous Point is
    typically not "on-link" for a particular router.  While much work
    has been done on multicast security for application-layer groups,
    little has been done to address the problem of managing hundreds
    or thousands of small one-to-many groups with link-local scope.
    Such an authentication mechanism should be considered along with
    the router-to-Rendezvous Point authentication mechanism.  The most
    important issue is ensuring that only the "authorized neighbors"
    get the keys for source/group (S,G), so that rogue routers cannot
    participate in the exchanges.  Another issue is that some of the
    communication may occur intra-domain, e.g., the link-local
    messages in an enterprise, while others for the same (*,G) may
    occur inter-domain, e.g., the router-to-Rendezvous Point messages
    may be from one enterprise's router to another.
    One possible solution proposes a region-wide "master" key server
    (possibly replicated), and one "local" key server per speaking
    router.  There is no issue with propagating the messages outside
    the link, because link-local messages, by definition, are not
    forwarded.  This solution is offered only as an example of how
    work may progress; further discussion should occur in this work
    team.  Specification of a link-local protection mechanism for PIM-
    SM is defined in [RFC4601], and this mechanism has been updated in
    PIM-SM-LINKLOCAL [RFC5796].  However, the KMP part is completely
    unspecified and will require work outside the expertise of the PIM
    working group to accomplish, another example of why this roadmap
    is being created.

6. Supporting Incremental Deployment

 It is imperative that the new authentication and security mechanisms
 defined support incremental deployment, as it is not feasible to
 deploy a new routing protocol authentication mechanism throughout the
 network instantaneously.  One of the goals of the KARP WG is to add
 incremental security to existing mechanisms rather than replacing
 them.  Delivering better deployable solutions to which vendors and
 operators can migrate is more important than getting a perfect
 security solution.  It may also not be possible to deploy such a
 mechanism to all routers in a large Autonomous System (AS) at one

Lebovitz & Bhatia Informational [Page 16] RFC 6518 KARP Design Guidelines February 2012

 time.  This means that the designers must work on this aspect of the
 authentication mechanism for the routing protocol on which they are
 working.  The mechanisms must provide backward compatibility in the
 message formatting, transmission, and processing of routing
 information carried through a mixed security environment.

7. Denial-of-Service Attacks

 DoS attacks must be kept in mind when designing KARP solutions.
 [THTS-REQS] describes DoS attacks that are in scope for the KARP
 work.  Protocol designers should ensure that the new cryptographic
 validation mechanisms must not provide an attacker with an
 opportunity for DoS attacks.  Cryptographic validation, while
 typically cheaper than signing, is still an incremental cost.  If an
 attacker can force a system to validate many packets multiple times,
 then this could be a potential DoS attack vector.  On the other hand,
 if the authentication procedure is itself quite CPU intensive, then
 overwhelming the CPU with multiple bogus packets can bring down the
 system.  In this case, the authentication procedure itself aids the
 DoS attack.
 There are some known techniques to reduce the cryptographic
 computation load.  Packets can include non-cryptographic consistency
 checks.  For example, [RFC5082] provides a mechanism that uses the IP
 header to limit the attackers that can inject packets that will be
 subject to cryptographic validation.  In the design, Phase 2, once an
 automated key management protocol is developed, it may be possible to
 determine the peer IP addresses that are valid participants.  Only
 the packets from the verified sources could be subject to
 cryptographic validation.
 Protocol designers must ensure that a device never needs to check
 incoming protocol packets using multiple keys, as this can overwhelm
 the CPU, leading to a DoS attack.  KARP solutions should indicate the
 checks that are appropriate prior to performing cryptographic
 validation.  KARP solutions should indicate where information about
 valid neighbors can be used to limit the scope of the attacks.
 Particular care needs to be paid to the design of automated key
 management schemes.  It is often desirable to force a party
 attempting to authenticate to do work and to maintain state until
 that work is done.  That is, the initiator of the authentication
 should maintain the cost of any state required by the authentication
 for as long as possible.  This also helps when an attacker sends an
 overwhelming load of keying protocol initiations from bogus sources.

Lebovitz & Bhatia Informational [Page 17] RFC 6518 KARP Design Guidelines February 2012

 Another important class of attack is denial of service against the
 routing protocol where an attacker can manipulate either the routing
 protocol or the cryptographic authentication mechanism to disrupt
 routing adjacencies.
 Without KARP solutions, many routing protocols are subject to
 disruption simply by injecting an invalid packet or a packet for the
 wrong state.  Even with cryptographic validation, replay attacks are
 often a vector where a previously valid packet can be injected to
 create a denial of service.   KARP solutions should prevent all cases
 where packet replays or other packet injections by an outsider can
 disrupt routing sessions.
 Some residual denial-of-service risk is always likely.  If an
 attacker can generate a large enough number of packets, the routing
 protocol can get disrupted.  Even if the routing protocol is not
 disrupted, the loss rate on a link may rise to a point where claiming
 that traffic can successfully be routed across the link will be
 inaccurate.

8. Gap Analysis

 The [THTS-REQS] document lists the generic requirements for the
 security mechanisms that must exist for the various routing protocols
 that come under the purview of KARP.  There will be different design
 teams working for each of the categories of routing protocols
 defined.
 To start, design teams must review the "Threats and Requirements for
 Authentication of routing protocols" document [THTS-REQS].  This
 document contains detailed descriptions of the threat analysis for
 routing protocol authentication and integrity in general.  Note that
 it does not contain all the authentication-related threats for any
 one routing protocol, or category of routing protocols.  The design
 team must conduct a protocol-specific threat analysis to determine if
 threats beyond those in the [THTS-REQS] document arise in the context
 of the protocol (group) and to describe those threats.
 The [THTS-REQS] document also contains many security requirements.
 Each routing protocol design team must walk through each section of
 the requirements and determine one by one how its protocol either
 does or does not relate to each requirement.
 Examples include modern, strong, cryptographic algorithms, with at
 least one such algorithm listed as a MUST, algorithm agility, secure
 use of simple PSKs, intra-connection replay protection, inter-
 connection replay protection, etc.

Lebovitz & Bhatia Informational [Page 18] RFC 6518 KARP Design Guidelines February 2012

 When doing the gap analysis, we must first identify the elements of
 each routing protocol that we wish to protect.  In case of protocols
 riding on top of IP, we might want to protect the IP header and the
 protocol headers, while for those that work on top of TCP, it will be
 the TCP header and the protocol payload.  There is patently value in
 protecting the IP header and the TCP header if the routing protocols
 rely on these headers for some information (for example, identifying
 the neighbor that originated the packet).
 Then, there will be a set of cryptography requirements that we might
 want to look at.  For example, there must be at least one set of
 cryptographic algorithms (MD5, SHA, etc.) or constructions (Hashed
 MAC (HMAC), etc.) whose use is supported by all implementations and
 can be safely assumed to be supported by any implementation of the
 authentication option.  The design teams should look for the protocol
 on which they are working.  If such algorithms or constructions are
 not available, then some should be defined to support
 interoperability by having a single default.
 Design teams must ensure that the default cryptographic algorithms
 and constructions supported by the routing protocols are accepted by
 the community.  This means that the protocols must not rely on non-
 standard or ad hoc hash functions, keyed-hash constructions,
 signature schemes, or other functions, and they must use published
 and standard schemes.
 Care should also be taken to ensure that the routing protocol
 authentication scheme has algorithm agility (i.e., it is capable of
 supporting algorithms other than its defaults).  Ideally, the
 authentication mechanism should not be affected by packet loss and
 reordering.
 Design teams should ensure that their protocol's authentication
 mechanism is able to accommodate rekeying.  This is essential since
 it is well known that keys must periodically be changed.  Also, what
 the designers must ensure is that this rekeying event should not
 affect the functioning of the routing protocol.  For example, OSPF
 rekeying requires coordination among the adjacent routers, while IS-
 IS requires coordination among routers in the entire domain.
 If new authentication and security mechanisms are needed, then the
 design teams must design in such a manner that the routing protocol
 authentication mechanism remains oblivious to how the keying material
 is derived.  This decouples the authentication mechanism from the key
 management system that is employed.

Lebovitz & Bhatia Informational [Page 19] RFC 6518 KARP Design Guidelines February 2012

 Design teams should also note that many routing protocols require
 prioritized treatment of certain protocol packets and authentication
 mechanisms should honor this.
 Not all routing protocol authentication mechanisms provide support
 for replay attacks, and the design teams should identify such
 authentication mechanisms and work on them so that this can get
 fixed.  The design teams must look at the protocols that they are
 working on and see if packets captured from the previous/stale
 sessions can be replayed.
 What might also influence the design is the rate at which the
 protocol packets are originated.  In case of protocols like BFD,
 where packets are originated at millisecond intervals, there are some
 special considerations that must be kept in mind when defining the
 new authentication and security mechanisms.
 The designers should also consider whether the current authentication
 mechanisms impose considerable processing overhead on a router that's
 doing authentication.  Most currently deployed routers do not have
 hardware accelerators for cryptographic processing and these
 operations can impose a significant processing burden under some
 circumstances.  The proposed solutions should be evaluated carefully
 with regard to the processing burden that they will impose, since
 deployment may be impeded if network operators perceive that a
 solution will impose a processing burden which either entails
 substantial capital expenses or threatens to destabilize the routers.

9. Security Considerations

 As mentioned in the Introduction, RFC 4948 [RFC4948] identifies
 additional steps needed to achieve the overall goal of improving the
 security of the core routing infrastructure.  Those include
 validation of route origin announcements, path validation, cleaning
 up the IRR databases for accuracy, and operational security practices
 that prevent routers from becoming compromised devices.  The KARP
 work is but one step needed to improve core routing infrastructure.
 The security of cryptographic-based systems depends on both the
 strength of the cryptographic algorithms chosen and the strength of
 the keys used with those algorithms.  The security also depends on
 the engineering of the protocol used by the system to ensure that
 there are no non-cryptographic ways to bypass the security of the
 overall system.

Lebovitz & Bhatia Informational [Page 20] RFC 6518 KARP Design Guidelines February 2012

9.1. Use Strong Keys

 Care should be taken to ensure that the selected key is
 unpredictable, avoiding any keys known to be weak for the algorithm
 in use.  [RFC4086] contains helpful information on both key
 generation techniques and cryptographic randomness.
 Care should also be taken when choosing the length of the key.
 [RFC3766] provides some additional information on asymmetric and
 symmetric key sizes and how they relate to system requirements for
 attack resistance.
 In addition to using a key of appropriate length and randomness,
 deployers of KARP should use different keys between different routing
 peers whenever operationally possible.  This is especially true when
 the routing protocol takes a static traffic key as opposed to a
 traffic key derived on a per-connection basis using a KDF.  The
 burden for doing so is understandably much higher than using the same
 static traffic key across all peering routers.  Depending upon the
 specific KMP, it can be argued that generally using a KMP network-
 wide increases peer-wise security.  Consider an attacker that learns
 or guesses the traffic key used by two peer routers: if the traffic
 key is only used between those two routers, then the attacker has
 only compromised that one connection not the entire network.
 However whenever using manual keys, it is best to design a system
 where a given pre-shared key (PSK) will be used in a KDF mixed with
 connection-specific material, in order to generate session unique --
 and therefore peer-wise -- traffic keys.  Doing so has the following
 advantages: the traffic keys used in the per-message authentication
 mechanism are peer-wise unique, it provides inter-connection replay
 protection, and if the per-message authentication mechanism covers
 some connection counter, intra-connection replay protection.
 Note that certain key derivation functions (e.g., KDF_AES_128_CMAC)
 as used in TCP-AO [RFC5926], the pseudorandom function (PRF) used in
 the KDF may require a key of a certain fixed size as an input.
 For example, AES_128_CMAC requires a 128-bit (16-byte) key as the
 seed.  However, for the convenience of the administrators, a
 specification may not want to require the entry of a PSK be of
 exactly 16 bytes.  Instead, a specification may call for a key prep
 routine that could handle a variable-length PSK, one that might be
 less or more than 16 bytes (see [RFC4615], Section 3, as an example).
 That key prep routine would derive a key of exactly the required
 length, thus, be suitable as a seed to the PRF.  This does NOT mean
 that administrators are safe to use weak keys.  Administrators are
 encouraged to follow [RFC4086] [NIST-800-118].  We simply attempted

Lebovitz & Bhatia Informational [Page 21] RFC 6518 KARP Design Guidelines February 2012

 to "put a fence around stupidity", as much as possible as it's hard
 to imagine administrators putting in a password that is, say 16 bytes
 in length.
 A better option, from a security perspective, is to use some
 representation of a device-specific asymmetric key pair as the
 identity proof, as described in section "Unique versus Shared Keys"
 section.

9.2. Internal versus External Operation

 Design teams must consider whether the protocol is an internal
 routing protocol or an external one, i.e., does it primarily run
 between peers within a single domain of control or between two
 different domains of control?  Some protocols may be used in both
 cases, internally and externally, and as such, various modes of
 authentication operation may be required for the same protocol.
 While it is preferred that all routing exchanges run with the best
 security mechanisms enabled in all deployment contexts, this
 exhortation is greater for those protocols running on inter-domain
 point-to-point links.  It is greatest for those on shared access link
 layers with several different domains interchanging together, because
 the volume of attackers are greater from the outside.  Note however,
 that the consequences of internal attacks maybe no less severe -- in
 fact, they may be quite a bit more severe -- than an external attack.
 An example of this internal versus external consideration is BGP,
 which has both EBGP and IBGP modes.  Another example is a multicast
 protocol where the neighbors are sometimes within a domain of control
 and sometimes at an inter-domain exchange point.  In the case of PIM-
 SM running on an internal multi-access link, it would be acceptable
 to give up some security to get some convenience by using a group key
 among the peers on the link.  On the other hand, in the case of PIM-
 SM running over a multi-access link at a public exchange point,
 operators may favor security over convenience by using unique pair-
 wise keys for every peer.  Designers must consider both modes of
 operation and ensure the authentication mechanisms fit both.
 Operators are encouraged to run cryptographic authentication on all
 their adjacencies, but to work from the outside in, i.e., External
 BGP (EBGP) links are a higher priority than the Internal BGP (IBGP)
 links because they are externally facing, and, as a result, more
 likely to be targeted in an attack.

9.3. Unique versus Shared Keys

 This section discusses security considerations regarding when it is
 appropriate to use the same authentication key inputs for multiple
 peers and when it is not.  This is largely a debate of convenience

Lebovitz & Bhatia Informational [Page 22] RFC 6518 KARP Design Guidelines February 2012

 versus security.  It is often the case that the best secured
 mechanism is also the least convenient mechanism.  For example, an
 air gap between a host and the network absolutely prevents remote
 attacks on the host, but having to copy and carry files using the
 "sneaker net" is quite inconvenient and does not scale.
 Operators have erred on the side of convenience when it comes to
 securing routing protocols with cryptographic authentication.  Many
 do not use it at all.  Some use it only on external links, but not on
 internal links.  Those that do use it often use the same key for all
 peers in a network.  It is common to see the same key in use for
 years, e.g., the key was entered when authentication mechanisms were
 originally configured or when the routing gear was deployed.
 One goal for designers is to create authentication and integrity
 mechanisms that are easy for operators to deploy and manage, and
 still use unique keys between peers (or small groups on multi-access
 links) and for different sessions among the same peers.  Operators
 have the impression that they NEED one key shared across the network,
 when, in fact, they do not.  What they need is the relative
 convenience they experience from deploying cryptographic
 authentication with one key (or a few keys) compared to the
 inconvenience they would experience if they deployed the same
 authentication mechanism using unique pair-wise keys.  An example is
 BGP route reflectors.  Here, operators often use the same
 authentication key between each client and the route reflector.  The
 roadmaps defined from this guidance document should allow for unique
 keys to be used between each client and the peer, without sacrificing
 much convenience.  Designers should strive to deliver peer-wise
 unique keying mechanisms with similar ease-of-deployment properties
 as today's one-key method.
 Operators must understand the consequences of using the same key
 across many peers.  One argument against using the same key is that
 if the same key that is used in multiple devices, then a compromise
 of any one of the devices will expose the key.  Also, since the same
 key is supported on many devices, this is known by many people, which
 affects its distribution to all of the devices.
 Consider also the attack consequence size, the amount of routing
 adjacencies that can be negatively affected once a breach has
 occurred, i.e., once the keys have been acquired by the attacker.
 Again, if a shared key is used across the internal domain, then the
 consequence size is the whole network.  Ideally, unique key pairs
 would be used for each adjacency.

Lebovitz & Bhatia Informational [Page 23] RFC 6518 KARP Design Guidelines February 2012

 In some cases, use of shared keys is needed because of the problem
 space.  For example, a multicast packet is sent once but then
 consumed by several routing neighbors.  If unique keys were used per
 neighbor, the benefit of multicast would be erased because the sender
 would have to create a different announcement packet for each
 receiver.  Though this may be desired and acceptable in some small
 number of use cases, it is not the norm.  Shared (i.e., group) keys
 are an acceptable solution here, and much work has been done already
 in this area (by the MSEC working group).

9.4. Key Exchange Mechanism

 This section discusses the security and use case considerations for
 key exchange for routing protocols.  Two options exist: an out-of-
 band mechanism or a KMP.  An out-of-band mechanism involves operators
 configuring keys in the device through a configuration tool or
 management method (e.g., Simple Network Management Protocol (SNMP),
 Network Configuration Protocol (NETCONF)).  A KMP is an automated
 protocol that exchanges keys without operator intervention.  KMPs can
 occur either in-band to the routing protocol or out-of-band to the
 routing protocol (i.e., a different protocol).
 An example of an out-of-band configuration mechanism could be an
 administrator who makes a remote management connection (e.g., using
 SSH) to a router and manually enters the keying information, e.g.,
 the algorithm, the key(s), the key lifetimes, etc.  Another example
 could be an OSS system that inputs the same information by using a
 script over an SSH connection or by pushing configuration through
 some other management connection, standard (NETCONF-based) or
 proprietary.
 The drawbacks of an out-of-band configuration mechanism include lack
 of scalability, complexity, and speed of changing if a security
 breach is suspected.  For example, if an employee who had access to
 keys was terminated, or if a machine holding those keys was believed
 to be compromised, then the system would be considered insecure and
 vulnerable until new keys were generated and distributed.  Those keys
 then need to be placed into the OSS system, and the OSS system then
 needs to push the new keys -- often during a very limited change
 window -- into the relevant devices.  If there are multiple
 organizations involved in these connections, because the protected
 connections are inter-domain, this process is very complicated.
 The principle benefit of out-of-band configuration mechanism is that
 once the new keys/parameters are set in OSS system, they can be
 pushed automatically to all devices within the OSS's domain.

Lebovitz & Bhatia Informational [Page 24] RFC 6518 KARP Design Guidelines February 2012

 Operators have mechanisms in place for this already for managing
 other router configuration data.  In small environments with few
 routers, a manual system is not difficult to employ.
 We further define a peer-to-peer KMP as using cryptographically
 protected identity verification, session key negotiation, and
 security association parameter negotiation between the two routing
 peers.  The KMP among peers may also include the negotiation of
 parameters, like cryptographic algorithms, cryptographic inputs
 (e.g., initialization vectors), key lifetimes, etc.
 There are several benefits of a peer-to-peer KMP versus centrally
 managed and distributing keys.  It results in key(s) that are
 privately generated, and it need not be recorded permanently
 anywhere.  Since the traffic keys used in a particular connection are
 not a fixed part of a device configuration, no security sensitive
 data exists anywhere else in the operator's systems that can be
 stolen, e.g., in the case of a terminated or turned employee.  If a
 server or other data store is stolen or compromised, the thieves gain
 limited or no access to current traffic keys.  They may gain access
 to key derivation material, like a PSK, but may not be able to access
 the current traffic keys in use.  In this example, these PSKs can be
 updated in the device configurations (either manually or through an
 OSS) without bouncing or impacting the existing session at all.  In
 the case of using raw asymmetric keys or certificates, instead of
 PSKs, the data theft (from the data store) would likely not result in
 any compromise, as the key pairs would have been generated on the
 routers and never leave those routers.  In such a case, no changes
 are needed on the routers; the connections will continue to be
 secure, uncompromised.  Additionally, with a KMP, regular rekey
 operations occur without any operator involvement or oversight.  This
 keeps keys fresh.
 There are a few drawbacks to using a KMP.  First, a KMP requires more
 cryptographic processing for the router at the beginning of a
 connection.  This will add some minor start-up time to connection
 establishment versus a purely manual key management approach.  Once a
 connection with traffic keys has been established via a KMP, the
 performance is the same in the KMP and the out-of-band configuration
 case.  KMPs also add another layer of protocol and configuration
 complexity, which can fail or be misconfigured.  This was more of an
 issue when these KMPs were first deployed, but less so as these
 implementations and operational experience with them have matured.
 One of the goals for KARP is to develop a KMP; an out-of-band
 configuration protocol for key exchange is out of scope.

Lebovitz & Bhatia Informational [Page 25] RFC 6518 KARP Design Guidelines February 2012

 Within this constraint, there are two approaches for a KMP:
 The first is to use a KMP that runs independent of the routing and
 the signaling protocols.  It would run on its own port and use its
 own transport (to avoid interfering with the routing protocol that it
 is serving).  When a routing protocol needs a key, it would contact
 the local instance of this key management protocol and request a key.
 The KMP generates a key that is delivered to the routing protocol for
 it to use for authenticating and integrity verification of the
 routing protocol packets.  This KMP could either be an existing key
 management protocol such as ISAKMP/IKE, GKMP, etc., extended for the
 routing protocols, or it could be a new KMP, designed for the routing
 protocol context.
 The second approach is to define an in-band KMP extension for
 existing routing protocols putting the key management mechanisms
 inside the protocol itself.  In this case, the key management
 messages would be carried within the routing protocol packets,
 resulting in very tight coupling between the routing protocols and
 the key management protocol.

10. Acknowledgments

 Much of the text for this document came originally from "Roadmap for
 Cryptographic Authentication of Routing Protocol Packets on the
 Wire", authored by Gregory M. Lebovitz.
 We would like to thank Sam Hartman, Eric Rescorla, Russ White, Sean
 Turner, Stephen Kent, Stephen Farrell, Adrian Farrel, Russ Housley,
 Michael Barnes, and Vishwas Manral for their comments on the
 document.

11. References

11.1. Normative References

 [RFC2119]      Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC4948]      Andersson, L., Davies, E., and L. Zhang, "Report from
                the IAB workshop on Unwanted Traffic March 9-10,
                2006", RFC 4948, August 2007.

11.2. Informative References

 [RFC1195]      Callon, R., "Use of OSI IS-IS for routing in TCP/IP
                and dual environments", RFC 1195, December 1990.

Lebovitz & Bhatia Informational [Page 26] RFC 6518 KARP Design Guidelines February 2012

 [RFC2205]      Braden, R., Ed., Zhang, L., Berson, S., Herzog, S.,
                and S. Jamin, "Resource ReSerVation Protocol (RSVP) --
                Version 1 Functional Specification", RFC 2205,
                September 1997.
 [RFC2328]      Moy, J., "OSPF Version 2", STD 54, RFC 2328, April
                1998.
 [RFC2453]      Malkin, G., "RIP Version 2", STD 56, RFC 2453,
                November 1998.
 [RFC2747]      Baker, F., Lindell, B., and M. Talwar, "RSVP
                Cryptographic Authentication", RFC 2747, January 2000.
 [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.
 [RFC3473]      Berger, L., Ed., "Generalized Multi-Protocol Label
                Switching (GMPLS) Signaling Resource ReserVation
                Protocol-Traffic Engineering (RSVP-TE) Extensions",
                RFC 3473, January 2003.
 [RFC3618]      Fenner, B., Ed., and D. Meyer, Ed., "Multicast Source
                Discovery Protocol (MSDP)", RFC 3618, October 2003.
 [RFC3766]      Orman, H. and P. Hoffman, "Determining Strengths For
                Public Keys Used For Exchanging Symmetric Keys", BCP
                86, RFC 3766, April 2004.
 [RFC3973]      Adams, A., Nicholas, J., and W. Siadak, "Protocol
                Independent Multicast - Dense Mode (PIM-DM): Protocol
                Specification (Revised)", RFC 3973, January 2005.
 [RFC4086]      Eastlake 3rd, D., Schiller, J., and S. Crocker,
                "Randomness Requirements for Security", BCP 106, RFC
                4086, June 2005.
 [RFC4107]      Bellovin, S. and R. Housley, "Guidelines for
                Cryptographic Key Management", BCP 107, RFC 4107, June
                2005.
 [RFC4230]      Tschofenig, H. and R. Graveman, "RSVP Security
                Properties", RFC 4230, December 2005.

Lebovitz & Bhatia Informational [Page 27] RFC 6518 KARP Design Guidelines February 2012

 [RFC4252]      Ylonen, T. and C. Lonvick, Ed., "The Secure Shell
                (SSH) Authentication Protocol", RFC 4252, January
                2006.
 [RFC4253]      Ylonen, T. and C. Lonvick, Ed., "The Secure Shell
                (SSH) Transport Layer Protocol", RFC 4253, January
                2006.
 [RFC4271]      Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
                Border Gateway Protocol 4 (BGP-4)", RFC 4271, January
                2006.
 [RFC4492]      Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C.,
                and B. Moeller, "Elliptic Curve Cryptography (ECC)
                Cipher Suites for Transport Layer Security (TLS)", RFC
                4492, May 2006.
 [RFC4601]      Fenner, B., Handley, M., Holbrook, H., and I.
                Kouvelas, "Protocol Independent Multicast - Sparse
                Mode (PIM-SM): Protocol Specification (Revised)", RFC
                4601, August 2006.
 [RFC4615]      Song, J., Poovendran, R., Lee, J., and T. Iwata, "The
                Advanced Encryption Standard-Cipher-based Message
                Authentication Code-Pseudo-Random Function-128 (-
                AES-CMAC-PRF-128) Algorithm for the Internet Key
                Exchange Protocol (IKE)", RFC 4615, August 2006.
 [RFC4726]      Farrel, A., Vasseur, J.-P., and A. Ayyangar, "A
                Framework for  Inter-Domain Multiprotocol Label
                Switching Traffic Engineering", RFC 4726, November
                2006.
 [RFC5036]      Andersson, L., Ed., Minei, I., Ed., and B. Thomas,
                Ed., "LDP Specification", RFC 5036, October 2007.
 [RFC5082]      Gill, V., Heasley, J., Meyer, D., Savola, P., Ed., and
                C. Pignataro, "The Generalized TTL Security Mechanism
                (GTSM)", RFC 5082, October 2007.
 [RFC5151]      Farrel, A., Ed., Ayyangar, A., and JP. Vasseur,
                "Inter-Domain MPLS and GMPLS Traffic Engineering --
                Resource Reservation Protocol-Traffic Engineering
                (RSVP-TE) Extensions", RFC 5151, February 2008.

Lebovitz & Bhatia Informational [Page 28] RFC 6518 KARP Design Guidelines February 2012

 [RFC5280]      Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
                Housley, R., and W. Polk, "Internet X.509 Public Key
                Infrastructure Certificate and Certificate Revocation
                List (CRL) Profile", RFC 5280, May 2008.
 [RFC5440]      Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path
                Computation Element (PCE) Communication Protocol
                (PCEP)", RFC 5440, March 2009.
 [RFC5796]      Atwood, W., Islam, S., and M. Siami, "Authentication
                and Confidentiality in Protocol Independent Multicast
                Sparse Mode (PIM-SM) Link-Local Messages", RFC 5796,
                March 2010.
 [RFC5880]      Katz, D. and D. Ward, "Bidirectional Forwarding
                Detection (BFD)", RFC 5880, June 2010.
 [RFC5925]      Touch, J., Mankin, A., and R. Bonica, "The TCP
                Authentication Option", RFC 5925, June 2010.
 [RFC5926]      Lebovitz, G. and E. Rescorla, "Cryptographic
                Algorithms for the TCP Authentication Option (TCP-
                AO)", RFC 5926, June 2010.
 [RFC6039]      Manral, V., Bhatia, M., Jaeggli, J., and R. White,
                "Issues with Existing Cryptographic Protection Methods
                for Routing Protocols", RFC 6039, October 2010.
 [RFC6407]      Weis, B., Rowles, S., and T. Hardjono, "The Group
                Domain of Interpretation", RFC 6407, October 2011.
 [THTS-REQS]    Lebovitz, G., "The Threat Analysis and Requirements
                for Cryptographic Authentication of Routing Protocols'
                Transports", Work in Progress, June 2011.
 [CRPT-TAB]     Housley, R. and Polk, T., "Database of Long-Lived
                Symmetric Cryptographic Keys", Work in Progress,
                October 2011
 [GDOI-MAC]     Weis, B. and S. Rowles, "GDOI Generic Message
                Authentication Code Policy", Work in Progress,
                September 2011.
 [IRR]          Merit Network Inc , "Internet Routing Registry Routing
                Assets Database", 2006, http://www.irr.net/.

Lebovitz & Bhatia Informational [Page 29] RFC 6518 KARP Design Guidelines February 2012

 [NIST-800-57]  US National Institute of Standards & Technology,
                "Recommendation for Key Management Part 1: General
                (Revised)", March 2007
 [NIST-800-118] US National Institute of Standards & Technology,
                "Guide to Enterprise Password Management (Draft)",
                April 2009

Authors' Addresses

 Gregory M. Lebovitz
 Aptos, California
 USA 95003
 EMail: gregory.ietf@gmail.com
 Manav Bhatia
 Alcatel-Lucent
 Bangalore
 India
 EMail: manav.bhatia@alcatel-lucent.com

Lebovitz & Bhatia Informational [Page 30]

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