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Network Working Group                                          M. BhatiaRequest for Comments: 5709                                Alcatel-LucentUpdates:2328                                                  V. ManralCategory: Standards Track                                    IP Infusion                                                                M. Fanto                                                     Aegis Data Security                                                                R. White                                                               M. Barnes                                                           Cisco Systems                                                                   T. Li                                                                Ericsson                                                             R. Atkinson                                                        Extreme Networks                                                            October 2009OSPFv2 HMAC-SHA Cryptographic AuthenticationAbstract   This document describes how the National Institute of Standards and   Technology (NIST) Secure Hash Standard family of algorithms can be   used with OSPF version 2's built-in, cryptographic authentication   mechanism.  This updates, but does not supercede, the cryptographic   authentication mechanism specified inRFC 2328.Status of This Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright and License Notice   Copyright (c) 2009 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 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 BSD License.Bhatia, et al.              Standards Track                     [Page 1]

RFC 5709                    OSPFv2 HMAC-SHA                 October 2009   This document may contain material from IETF Documents or IETF   Contributions published or made publicly available before November   10, 2008.  The person(s) controlling the copyright in some of this   material may not have granted the IETF Trust the right to allow   modifications of such material outside the IETF Standards Process.   Without obtaining an adequate license from the person(s) controlling   the copyright in such materials, this document may not be modified   outside the IETF Standards Process, and derivative works of it may   not be created outside the IETF Standards Process, except to format   it for publication as an RFC or to translate it into languages other   than English.1.  Introduction   A variety of risks exist when deploying any routing protocol   [Bell89].  This document provides an update to OSPFv2 Cryptographic   Authentication, which is specified inAppendix D of RFC 2328.  This   document does not deprecate or supercedeRFC 2328.  OSPFv2, itself,   is defined inRFC 2328 [RFC2328].   This document adds support for Secure Hash Algorithms (SHA) defined   in the US NIST Secure Hash Standard (SHS), which is defined by NIST   FIPS 180-2.  [FIPS-180-2] includes SHA-1, SHA-224, SHA-256, SHA-384,   and SHA-512.  The Hashed Message Authentication Code (HMAC)   authentication mode defined in NIST FIPS 198 is used [FIPS-198].   It is believed that [RFC2104] is mathematically identical to   [FIPS-198] and it is also believed that algorithms in [RFC4634] are   mathematically identical to [FIPS-180-2].   The creation of this addition to OSPFv2 was driven by operator   requests that they be able to use the NIST SHS family of algorithms   in the NIST HMAC mode, instead of being forced to use the Keyed-MD5   algorithm and mode with OSPFv2 Cryptographic Authentication.   Cryptographic matters are discussed in more detail in the Security   Considerations section of 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 inRFC 2119 [RFC2119].2.  Background   All OSPF protocol exchanges can be authenticated.  The OSPF packet   header (seeAppendix A.3.1 of RFC 2328) includes an Authentication   Type field and 64 bits of data for use by the appropriate   authentication scheme (determined by the Type field).Bhatia, et al.              Standards Track                     [Page 2]

RFC 5709                    OSPFv2 HMAC-SHA                 October 2009   The authentication type is configurable on a per-interface (or,   equivalently, on a per-network/subnet) basis.  Additional   authentication data is also configurable on a per-interface basis.   OSPF authentication types 0, 1, and 2 are defined byRFC 2328.  This   document provides an update toRFC 2328 that is only applicable to   Authentication Type 2, "Cryptographic Authentication".3.  Cryptographic Authentication with NIST SHS in HMAC Mode   Using this authentication type, a shared secret key is configured in   all routers attached to a common network/subnet.  For each OSPF   protocol packet, the key is used to generate/verify a "message   digest" that is appended to the end of the OSPF packet.  The message   digest is a one-way function of the OSPF protocol packet and the   secret key.  Since the secret key is never sent over the network in   the clear, protection is provided against passive attacks [RFC1704].   The algorithms used to generate and verify the message digest are   specified implicitly by the secret key.  This specification discusses   the computation of OSPFv2 Cryptographic Authentication data when any   of the NIST SHS family of algorithms is used in the Hashed Message   Authentication Code (HMAC) mode.  Please also seeRFC 2328, Appendix D.   With the additions in this document, the currently valid algorithms   (including mode) for OSPFv2 Cryptographic Authentication include:           Keyed-MD5               (defined inRFC 2328, Appendix D)           HMAC-SHA-1              (defined here)           HMAC-SHA-256            (defined here)           HMAC-SHA-384            (defined here)           HMAC-SHA-512            (defined here)   Of the above, implementations of this specification MUST include   support for at least:           HMAC-SHA-256   and SHOULD include support for:           HMAC-SHA-1   and SHOULD also (for backwards compatibility with existing   implementations and deployments) include support for:           Keyed-MD5Bhatia, et al.              Standards Track                     [Page 3]

RFC 5709                    OSPFv2 HMAC-SHA                 October 2009   and MAY also include support for:           HMAC-SHA-384           HMAC-SHA-512   An implementation of this specification MUST allow network operators   to configure ANY authentication algorithm supported by that   implementation for use with ANY given KeyID value that is configured   into that OSPFv2 router.3.1.  Generating Cryptographic Authentication   The overall cryptographic authentication process defined inAppendixD of RFC 2328 remains unchanged.  However, the specific cryptographic   details (i.e., SHA rather than MD5, HMAC rather than Keyed-Hash) are   defined herein.  To reduce the potential for confusion, this section   minimises the repetition of text fromRFC 2328, Appendix D, which is   incorporated here by reference [RFC2328].   First, following the procedure defined inRFC 2328, Appendix D,   select the appropriate OSPFv2 Security Association for use with this   packet and set the KeyID field to the KeyID value of that OSPFv2   Security Association.   Second, set the Authentication Type to Cryptographic Authentication,   and set the Authentication Data Length field to the length (measured   in bytes, not bits) of the cryptographic hash that will be used.   When any NIST SHS algorithm is used in HMAC mode with OSPFv2   Cryptographic Authentication, the Authentication Data Length is equal   to the normal hash output length (measured in bytes) for the specific   NIST SHS algorithm in use.  For example, with NIST SHA-256, the   Authentication Data Length is 32 bytes.   Third, the 32-bit cryptographic sequence number is set in accordance   with the procedures inRFC 2328, Appendix D that are applicable to   the Cryptographic Authentication type.   Fourth, the message digest is then calculated and appended to the   OSPF packet, as described below inSection 3.3.  The KeyID,   Authentication Algorithm, and Authentication Key to be used for   calculating the digest are all components of the selected OSPFv2   Security Association.  Input to the authentication algorithm consists   of the OSPF packet and the secret key.Bhatia, et al.              Standards Track                     [Page 4]

RFC 5709                    OSPFv2 HMAC-SHA                 October 20093.2.  OSPFv2 Security Association   This document uses the term OSPFv2 Security Association (OSPFv2 SA)   to refer to the authentication key information defined in Section D.3   ofRFC 2328.  The OSPFv2 protocol does not include an in-band   mechanism to create or manage OSPFv2 Security Associations.  The   parameters of an OSPFv2 Security Association are updated to be:   Key Identifier (KeyID)      This is an 8-bit unsigned value used to uniquely identify an      OSPFv2 SA and is configured either by the router administrator      (or, in the future, possibly by some key management protocol      specified by the IETF).  The receiver uses this to locate the      appropriate OSPFv2 SA to use.  The sender puts this KeyID value in      the OSPF packet based on the active OSPF configuration.   Authentication Algorithm      This indicates the authentication algorithm (and also the      cryptographic mode, such as HMAC) to be used.  This information      SHOULD never be sent over the wire in cleartext form.  At present,      valid values are Keyed-MD5, HMAC-SHA-1, HMAC-SHA-256, HMAC-SHA-      384, and HMAC-SHA-512.   Authentication Key      This is the cryptographic key used for cryptographic      authentication with this OSPFv2 SA.  This value SHOULD never be      sent over the wire in cleartext form.  This is noted as "K" inSection 3.3 below.   Key Start Accept      The time that this OSPF router will accept packets that have been      created with this OSPF Security Association.   Key Start Generate      The time that this OSPF router will begin using this OSPF Security      Association for OSPF packet generation.   Key Stop Generate      The time that this OSPF router will stop using this OSPF Security      Association for OSPF packet generation.   Key Stop Accept      The time that this OSPF router will stop accepting packets      generated with this OSPF Security Association.   In order to achieve smooth key transition, KeyStartAccept SHOULD be   less than KeyStartGenerate and KeyStopGenerate SHOULD be less than   KeyStopAccept.  If KeyStopGenerate and KeyStopAccept are leftBhatia, et al.              Standards Track                     [Page 5]

RFC 5709                    OSPFv2 HMAC-SHA                 October 2009   unspecified, the key's lifetime is infinite.  When a new key replaces   an old, the KeyStartGenerate time for the new key MUST be less than   or equal to the KeyStopGenerate time of the old key.   Key storage SHOULD persist across a system restart, warm or cold, to   avoid operational issues.  In the event that the last key associated   with an interface expires, it is unacceptable to revert to an   unauthenticated condition, and not advisable to disrupt routing.   Therefore, the router should send a "last Authentication Key   expiration" notification to the network manager and treat the key as   having an infinite lifetime until the lifetime is extended, the key   is deleted by network management, or a new key is configured.3.3.  Cryptographic Aspects   This describes the computation of the Authentication Data value when   any NIST SHS algorithm is used in the HMAC mode with OSPFv2   Cryptographic Authentication.   In the algorithm description below, the following nomenclature, which   is consistent with [FIPS-198], is used:      H    is the specific hashing algorithm (e.g., SHA-256).      K    is the Authentication Key for the OSPFv2 security           association.      Ko   is the cryptographic key used with the hash algorithm.      B    is the block size of H, measured in octets           rather than bits.  Note well that B is the           internal block size, not the hash size.              For SHA-1 and SHA-256: B == 64              For SHA-384 and SHA-512: B == 128      L    is the length of the hash, measured in octets           rather than bits.      XOR  is the exclusive-or operation.      Opad is the hexadecimal value 0x5c repeated B times.      Ipad is the hexadecimal value 0x36 repeated B times.      Apad is the hexadecimal value 0x878FE1F3 repeated (L/4) times.Bhatia, et al.              Standards Track                     [Page 6]

RFC 5709                    OSPFv2 HMAC-SHA                 October 2009      Implementation note:         This definition of Apad means that Apad is always the same         length as the hash output.   (1) PREPARATION OF KEY       In this application, Ko is always L octets long.       If the Authentication Key (K) is L octets long, then Ko is equal       to K.  If the Authentication Key (K) is more than L octets long,       then Ko is set to H(K).  If the Authentication Key (K) is less       than L octets long, then Ko is set to the Authentication Key (K)       with zeros appended to the end of the Authentication Key (K),       such that Ko is L octets long.   (2) FIRST-HASH       First, the OSPFv2 packet's Authentication Trailer (which is the       appendage described inRFC 2328, Section D.4.3, Page 233, items       (6)(a) and (6)(d)) is filled with the value Apad, and the       Authentication Type field is set to 2.       Then, a First-Hash, also known as the inner hash, is computed as       follows:             First-Hash = H(Ko XOR Ipad || (OSPFv2 Packet))       Implementation Notes:          Note that the First-Hash above includes the Authentication          Trailer containing the Apad value, as well as the OSPF packet,          as perRFC 2328, Section D.4.3.       The definition of Apad (above) ensures it is always the same       length as the hash output.  This is consistent withRFC 2328.       The "(OSPFv2 Packet)" mentioned in the First-Hash (above) does       include the OSPF Authentication Trailer.       The digest length for SHA-1 is 20 bytes; for SHA-256, 32 bytes;       for SHA-384, 48 bytes; and for SHA-512, 64 bytes.   (3) SECOND-HASH       Then a Second-Hash, also known as the outer hash, is computed as       follows:             Second-Hash = H(Ko XOR Opad || First-Hash)Bhatia, et al.              Standards Track                     [Page 7]

RFC 5709                    OSPFv2 HMAC-SHA                 October 2009   (4) RESULT       The resulting Second-Hash becomes the Authentication Data that is       sent in the Authentication Trailer of the OSPFv2 packet.  The       length of the Authentication Trailer is always identical to the       message digest size of the specific hash function H that is being       used.       This also means that the use of hash functions with larger output       sizes will also increase the size of the OSPFv2 packet as       transmitted on the wire.       Implementation Note:RFC 2328, Appendix D specifies that the Authentication Trailer          is not counted in the OSPF packet's own Length field, but is          included in the packet's IP Length field.3.4.  Message Verification   Message verification follows the procedure defined inRFC 2328,   except that the cryptographic calculation of the message digest   follows the procedure inSection 3.3 above when any NIST SHS   algorithm in the HMAC mode is in use.  Kindly recall that the   cryptographic algorithm/mode in use is indicated implicitly by the   KeyID of the received OSPFv2 packet.   Implementation Notes:      One must save the received digest value before calculating the      expected digest value, so that after that calculation the received      value can be compared with the expected value to determine whether      to accept that OSPF packet.RFC 2328, Section D.4.3 (6) (c) should be read very closely prior      to implementing the above.  With SHA algorithms in HMAC mode, Apad      is placed where the MD5 key would be put if Keyed-MD5 were in use.3.5.  Changing OSPFv2 Security Associations   Using KeyIDs makes changing the active OSPFv2 SA convenient.  An   implementation can choose to associate a lifetime with each OSPFv2 SA   and can thus automatically switch to a different OSPFv2 SA based on   the lifetimes of the configured OSPFv2 SA(s).   After changing the active OSPFv2 SA, the OSPF sender will use the   (different) KeyID value associated with the newly active OSPFv2 SA.   The receiver will use this new KeyID to select the appropriate (new)   OSPFv2 SA to use with the received OSPF packet containing the new   KeyID value.Bhatia, et al.              Standards Track                     [Page 8]

RFC 5709                    OSPFv2 HMAC-SHA                 October 2009   Because the KeyID field is present, the receiver does not need to try   all configured OSPFv2 Security Associations with any received OSPFv2   packet.  This can mitigate some of the risks of a Denial-of-Service   (DoS) attack on the OSPF instance, but does not entirely prevent all   conceivable DoS attacks.  For example, an on-link adversary still   could generate OSPFv2 packets that are syntactically valid but that   contain invalid Authentication Data, thereby forcing the receiver(s)   to perform expensive cryptographic computations to discover that the   packets are invalid.4.  Security Considerations   This document enhances the security of the OSPFv2 routing protocol by   adding, to the existing OSPFv2 Cryptographic Authentication method,   support for the algorithms defined in the NIST Secure Hash Standard   (SHS) using the Hashed Message Authentication Code (HMAC) mode, and   by adding support for the Hashed Message Authentication Code (HMAC)   mode.   This provides several alternatives to the existing Keyed-MD5   mechanism.  There are published concerns about the overall strength   of the MD5 algorithm ([Dobb96a], [Dobb96b], [Wang04]).  While those   published concerns apply to the use of MD5 in other modes (e.g., use   of MD5 X.509v3/PKIX digital certificates), they are not an attack   upon Keyed-MD5, which is what OSPFv2 specified inRFC 2328.  There   are also published concerns about the SHA algorithm [Wang05] and also   concerns about the MD5 and SHA algorithms in the HMAC mode ([RR07],   [RR08]).  Separately, some organisations (e.g., the US government)   prefer NIST algorithms, such as the SHA family, over other algorithms   for local policy reasons.   The value Apad is used here primarily for consistency with IETF   specifications for HMAC-SHA authentication of RIPv2 SHA [RFC4822] and   IS-IS SHA [RFC5310] and to minimise OSPF protocol processing changes   in Section D.4.3 ofRFC 2328 [RFC2328].   The quality of the security provided by the Cryptographic   Authentication option depends completely on the strength of the   cryptographic algorithm and cryptographic mode in use, the strength   of the key being used, and the correct implementation of the security   mechanism in all communicating OSPF implementations.  Accordingly,   the use of high assurance development methods is recommended.  It   also requires that all parties maintain the secrecy of the shared   secret key.  [RFC4086] provides guidance on methods for generating   cryptographically random bits.Bhatia, et al.              Standards Track                     [Page 9]

RFC 5709                    OSPFv2 HMAC-SHA                 October 2009   This mechanism is vulnerable to a replay attack by any on-link node.   An on-link node could record a legitimate OSPF packet sent on the   link, then replay that packet at the next time the recorded OSPF   packet's sequence number is valid.  This replay attack could cause   significant routing disruptions within the OSPF domain.   Ideally, for example, to prevent the preceding attack, each OSPF   Security Association would be replaced by a new and different OSPF   Security Association before any sequence number were reused.  As of   the date this document was published, no form of automated key   management has been standardised for OSPF.  So, as of the date this   document was published, common operational practice has been to use   the same OSPF Authentication Key for very long periods of time.  This   operational practice is undesirable for many reasons.  Therefore, it   is clearly desirable to develop and standardise some automated key-   management mechanism for OSPF.   Because all of the currently specified algorithms use symmetric   cryptography, one cannot authenticate precisely which OSPF router   sent a given packet.  However, one can authenticate that the sender   knew the OSPF Security Association (including the OSPFv2 SA's   parameters) currently in use.   Because a routing protocol contains information that need not be kept   secret, privacy is not a requirement.  However, authentication of the   messages within the protocol is of interest in order to reduce the   risk of an adversary compromising the routing system by deliberately   injecting false information into the routing system.   The technology in this document enhances an authentication mechanism   for OSPFv2.  The mechanism described here is not perfect and need not   be perfect.  Instead, this mechanism represents a significant   increase in the work function of an adversary attacking OSPFv2, as   compared with plain-text authentication or null authentication, while   not causing undue implementation, deployment, or operational   complexity.  Denial-of-Service attacks are not generally preventable   in a useful networking protocol [VK83].   Because of implementation considerations, including the need for   backwards compatibility, this specification uses the same mechanism   as specified inRFC 2328 and limits itself to adding support for   additional cryptographic hash functions.  Also, some large network   operators have indicated they prefer to retain the basic mechanism   defined inRFC 2328, rather than migrate to IP Security, due to   deployment and operational considerations.  If all the OSPFv2 routers   supported IPsec, then IPsec tunnels could be used in lieu of this   mechanism [RFC4301].  This would, however, relegate the topology to   point-to-point adjacencies over the mesh of IPsec tunnels.Bhatia, et al.              Standards Track                    [Page 10]

RFC 5709                    OSPFv2 HMAC-SHA                 October 2009   If a stronger authentication were believed to be required, then the   use of a full digital signature [RFC2154] would be an approach that   should be seriously considered.  Use of full digital signatures would   enable precise authentication of the OSPF router originating each   OSPF link-state advertisement, and thereby provide much stronger   integrity protection for the OSPF routing domain.5.  IANA Considerations   The OSPF Authentication Codes registry entry for Cryptographic   Authentication (Registry Code 2) has been updated to refer to this   document as well as toRFC 2328.6.  Acknowledgements   The authors would like to thank Bill Burr, Tim Polk, John Kelsey, and   Morris Dworkin of (US) NIST for review of portions of this document   that are directly derived from the closely related work on RIPv2   Cryptographic Authentication [RFC4822].   David Black, Nevil Brownlee, Acee Lindem, and Hilarie Orman (in   alphabetical order by last name) provided feedback on earlier   versions of this document.  That feedback has greatly improved both   the technical content and the readability of the current document.   Henrik Levkowetz's Internet Draft tools were very helpful in   preparing this document and are much appreciated.7.  References7.1.  Normative References   [FIPS-180-2] US National Institute of Standards & Technology, "Secure                Hash Standard (SHS)", FIPS PUB 180-2, August 2002.   [FIPS-198]   US National Institute of Standards & Technology, "The                Keyed-Hash Message Authentication Code (HMAC)", FIPS PUB                198, March 2002.   [RFC2119]    Bradner, S., "Key words for use in RFCs to Indicate                Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC2328]    Moy, J., "OSPF Version 2", STD 54,RFC 2328, April 1998.Bhatia, et al.              Standards Track                    [Page 11]

RFC 5709                    OSPFv2 HMAC-SHA                 October 20097.2.  Informative References   [Bell89]     Bellovin, S., "Security Problems in the TCP/IP Protocol                Suite", ACM Computer Communications Review, Volume 19,                Number 2, pp. 32-48, April 1989.   [Dobb96a]    Dobbertin, H, "Cryptanalysis of MD5 Compress", Technical                Report, 2 May 1996. (Presented at the Rump Session of                EuroCrypt 1996.)   [Dobb96b]    Dobbertin, H, "The Status of MD5 After a Recent Attack",                CryptoBytes, Vol. 2, No. 2, Summer 1996.   [RFC1704]    Haller, N. and R. Atkinson, "On Internet                Authentication",RFC 1704, October 1994.   [RFC2104]    Krawczyk, H., Bellare, M., and R. Canetti, "HMAC:                Keyed-Hashing for Message Authentication",RFC 2104,                February 1997.   [RFC2154]    Murphy, S., Badger, M., and B. Wellington, "OSPF with                Digital Signatures",RFC 2154, June 1997.   [RFC4086]    Eastlake, D., 3rd, Schiller, J., and S. Crocker,                "Randomness Requirements for Security",BCP 106,RFC4086, June 2005.   [RFC4301]    Kent, S. and K. Seo, "Security Architecture for the                Internet Protocol",RFC 4301, December 2005.   [RFC4634]    Eastlake 3rd, D. and T. Hansen, "US Secure Hash                Algorithms (SHA and HMAC-SHA)",RFC 4634, July 2006.   [RFC4822]    Atkinson, R. and M. Fanto, "RIPv2 Cryptographic                Authentication",RFC 4822, February 2007.   [RFC5310]    Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,                and M. Fanto, "IS-IS Generic Cryptographic                Authentication",RFC 5310, February 2009.   [RR07]       Rechberger, C. and V. Rijmen, "On Authentication with                HMAC and Non-random Properties", Financial Cryptography                and Data Security, Lecture Notes in Computer Science,                Volume 4886/2008, Springer-Verlag, Berlin, December                2007.Bhatia, et al.              Standards Track                    [Page 12]

RFC 5709                    OSPFv2 HMAC-SHA                 October 2009   [RR08]       Rechberger, C. and V. Rijmen, "New Results on NMAC/HMAC                when Instantiated with Popular Hash Functions", Journal                of Universal Computer Science, Volume 14, Number 3, pp.                347-376, 1 February 2008.   [VK83]       Voydock, V. and S. Kent, "Security Mechanisms in High-                level Networks", ACM Computing Surveys, Vol. 15, No. 2,                June 1983.   [Wang04]     Wang, X., et alia, "Collisions for Hash Functions MD4,                MD5, HAVAL-128, and RIPEMD", August 2004, IACR,http://eprint.iacr.org/2004/199   [Wang05]     Wang, X., et alia, "Finding Collisions in the Full SHA-                1" Proceedings of Crypto 2005, Lecture Notes in Computer                Science, Volume 3621, pp. 17-36, Springer-Verlag,                Berlin, August 31, 2005.Authors' Addresses   Manav Bhatia   Alcatel-Lucent   Bangalore,   India   EMail: manav.bhatia@alcatel-lucent.com   Vishwas Manral   IP Infusion   Almora, Uttarakhand   India   EMail: vishwas@ipinfusion.com   Matthew J. Fanto   Aegis Data Security   Dearborn, MI   USA   EMail: mfanto@aegisdatasecurity.comBhatia, et al.              Standards Track                    [Page 13]

RFC 5709                    OSPFv2 HMAC-SHA                 October 2009   Russ I. White   Cisco Systems   7025 Kit Creek Road   P.O. Box 14987   RTP, NC   27709 USA   EMail: riw@cisco.com   M. Barnes   Cisco Systems   225 West Tasman Drive   San Jose, CA   95134  USA   EMail: mjbarnes@cisco.com   Tony Li   Ericsson   300 Holger Way   San Jose, CA   95134  USA   EMail: tony.li@tony.li   Randall J. Atkinson   Extreme Networks   3585 Monroe Street   Santa Clara, CA   95051  USA   Phone: +1 (408) 579-2800   EMail: rja@extremenetworks.comBhatia, et al.              Standards Track                    [Page 14]