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Internet Engineering Task Force (IETF)                      S. GulrajaniRequest for Comments: 6395                                     S. VenaasCategory: Standards Track                                  Cisco SystemsISSN: 2070-1721                                             October 2011An Interface Identifier (ID) Hello Option for PIMAbstract   This document defines a new PIM Hello option to advertise an   Interface Identifier that can be used by PIM protocols to uniquely   identify an interface of a neighboring router.Status of This Memo   This is an Internet Standards Track document.   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).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6395.Copyright Notice   Copyright (c) 2011 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 Simplified BSD License.Gulrajani & Venaas           Standards Track                    [Page 1]

RFC 6395          An Interface ID Hello Option for PIM      October 2011Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .21.1.  Requirements Notation . . . . . . . . . . . . . . . . . . .22.  Interface Identifier Option . . . . . . . . . . . . . . . . . .22.1.  Local Interface Identifier  . . . . . . . . . . . . . . . .32.2.  Router Identifier . . . . . . . . . . . . . . . . . . . . .33.  Message Format  . . . . . . . . . . . . . . . . . . . . . . . .44.  Security Considerations . . . . . . . . . . . . . . . . . . . .45.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .56.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . .57.  References  . . . . . . . . . . . . . . . . . . . . . . . . . .57.1.  Normative References  . . . . . . . . . . . . . . . . . . .57.2.  Informative References  . . . . . . . . . . . . . . . . . .51.  Introduction   This document defines a new option for use in PIM Hello messages   [RFC4601] to carry an Interface Identifier.  A router generates   identifiers for each of its PIM-enabled interfaces such that each   interface has a different identifier.  The identifiers can optionally   be generated such that they are unique within, e.g., an   administrative domain.   An example where this Interface Identifier can be used is with PIM   over Reliable Transport (PORT) [PIM-PORT], where a single Transport   connection is used between two routers that have multiple interfaces   connecting them.  If these interfaces have unnumbered or IPv6 link-   local addresses, the Interface Identifier included in the PORT Join/   Prune message will identify with which interface the message is   associated.  For PORT, the Router Identifier is not needed, and it   can be set to zero.   All multi-byte integers in this specification are transmitted in   network byte order (i.e., most significant byte first).1.1.  Requirements Notation   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 [RFC2119].2.  Interface Identifier Option   The Interface Identifier option is used to identify the interface of   a neighboring router through which a PIM Hello [RFC4601] was sent.   This allows PIM protocols to refer to, or identify, a particular   interface on a neighboring router.Gulrajani & Venaas           Standards Track                    [Page 2]

RFC 6395          An Interface ID Hello Option for PIM      October 2011   The Interface Identifier option need only be included in PIM Hello   messages if the router supports protocols that require it.  An   implementation MAY choose to always include it.  The usage of the   Interface Identifier and the uniqueness requirements are left to the   specifications of the PIM protocols that implement it.  It is assumed   that different protocols have different minimum requirements for   stability and uniqueness of the Interface Identifier but that they   have no maximum requirement.  When specified, these protocols should   indicate what their minimum requirements are.   The Interface Identifier consists of 64 bits.  The lower 32 bits form   a Local Interface Identifier, and the high 32 bits form a Router   Identifier.2.1.  Local Interface Identifier   The 32-bit Local Interface Identifier is selected such that it is   unique among the router's PIM-enabled interfaces.  That is, there   MUST NOT be two PIM interfaces with the same Local Interface   Identifier.  While an interface is up, the Identifier MUST always be   the same once it has been allocated.  If an interface goes down and   comes up, the router SHOULD use the same Identifier.  If a node goes   down and comes up again, the Identifier for each interface MAY   change.  Many systems make use of an ifIndex [RFC2863] as a Local   Interface Identifier.   The Local Interface Identifier MUST be non-zero.  The reason for this   is that some protocols may have messages that optionally reference an   Interface Identifier, and they may use the value of 0 to show that no   Interface Identifier is being referenced.  Note that the value of 0   is not a valid ifIndex as defined in [RFC2863].2.2.  Router Identifier   The 32-bit Router Identifier may be used to uniquely identify the   router.  The requirements for the scope in which the Router   Identifier needs to be unique depend on the protocols that utilize   it.  It may need to be unique within some administrative domain, or   it may possibly be globally unique.   A router implementation selects a Router Identifier according to a   configured policy that defines the uniqueness scope.  Thus, an   implementation MAY be configured to choose an IPv4 unicast address   assigned to the router as the Router Identifier, but the   implementation MUST allow the identifier to be configured manually.Gulrajani & Venaas           Standards Track                    [Page 3]

RFC 6395          An Interface ID Hello Option for PIM      October 2011   Protocols such as BGP [RFC4271] and OSPFv2 [RFC2328] are other   protocols that make use of 32-bit identifiers for routers.  Provided   that the stability and uniqueness requirements of the protocols that   make use of the Router Identifier are met, an implementation MAY use   the same identifier used by other protocols.   The value 0 has a special meaning for the Router Identifier.  It   means that no Router Identifier is used.  If a router only supports   protocols that require the Interface Identifier to be unique for one   router (only making use of the Local Interface Identifier), then the   implementation MAY set the Router Identifier to zero.3.  Message Format   Option Type: Interface Identifier     0                   1                   2                   3     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    |           Type = 31           |         Length = 8            |    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    |                       Router Identifier                       |    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+    |                   Local Interface Identifier                  |    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   Allocated Hello Type values can be found in [HELLO-OPT].   Length:   In bytes for the value part of the Type/Length/Value      encoding.  The Interface Identifier will be 8 bytes long.   Router Identifier:   The Router Identifier is a 4-byte identifier      uniquely identifying the router within some scope.  It MAY be 0      when no protocols require a Router Identifier.  The field MUST      contain a valid Router Identifier or the value zero.   Local Interface Identifier:   The Local Interface Identifier is a      4-byte identifier that is unique among all PIM-enabled interfaces      on a router.4.  Security Considerations   The Interface Identifier is included in PIM Hello messages.  See   [RFC4601] for security considerations regarding PIM Hello messages.   In particular, PIM Hello messages may be forged and include an   arbitrary Interface Identifier, or the Interface Identifier may be   intentionally omitted.  The effects of this depend on how the   Interface Identifier is used by other protocols.Gulrajani & Venaas           Standards Track                    [Page 4]

RFC 6395          An Interface ID Hello Option for PIM      October 20115.  IANA Considerations   IANA has assigned the value 31 for the Interface ID PIM-Hello option   defined in this document.6.  Acknowledgments   The authors thank Yiqun Cai, Heidi Ou, Liming Wei, Gorry Fairhurst,   Bharat Joshi, and Bill Atwood for providing valuable feedback.7.  References7.1.  Normative References   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate               Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC4601]   Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,               "Protocol Independent Multicast - Sparse Mode (PIM-SM):               Protocol Specification (Revised)",RFC 4601, August 2006.7.2.  Informative References   [HELLO-OPT] IANA, "PIM Hello Options", <http://www.iana.org/>.   [PIM-PORT]  Farinacci, D., Wijnands, IJ., Venaas, S., and M.               Napierala, "A Reliable Transport Mechanism for PIM", Work               in Progress, August 2011.   [RFC2328]   Moy, J., "OSPF Version 2", STD 54,RFC 2328, April 1998.   [RFC2863]   McCloghrie, K. and F. Kastenholz, "The Interfaces Group               MIB",RFC 2863, June 2000.   [RFC4271]   Rekhter, Y., Li, T., and S. Hares, "A Border Gateway               Protocol 4 (BGP-4)",RFC 4271, January 2006.Gulrajani & Venaas           Standards Track                    [Page 5]

RFC 6395          An Interface ID Hello Option for PIM      October 2011Authors' Addresses   Sameer Gulrajani   Cisco Systems   Tasman Drive   San Jose, CA  95134   USA   EMail: sameerg@cisco.com   Stig Venaas   Cisco Systems   Tasman Drive   San Jose, CA  95134   USA   EMail: stig@cisco.comGulrajani & Venaas           Standards Track                    [Page 6]