Internet Engineering Task Force (IETF) S. Gulrajani

Internet Engineering Task Force (IETF) S. Gulrajani
Request for Comments: 6395 S. Venaas
Category: Standards Track Cisco Systems
ISSN: 2070-1721 October 2011

An Interface Identifier (ID) Hello Option for PIM

Abstract

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 in 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/rfc6395.

Copyright Notice

Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.

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RFC 6395 An Interface ID Hello Option for PIM October 2011

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Notation . . . . . . . . . . . . . . . . . . . 2
2. Interface Identifier Option . . . . . . . . . . . . . . . . . . 2
2.1. Local Interface Identifier . . . . . . . . . . . . . . . . 3
2.2. Router Identifier . . . . . . . . . . . . . . . . . . . . . 3
3. Message Format . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . . 5

1. 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.

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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.

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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.

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RFC 6395 An Interface ID Hello Option for PIM October 2011

5. 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. References

7.1. 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.

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RFC 6395 An Interface ID Hello Option for PIM October 2011

Authors' Addresses

Sameer Gulrajani
Cisco Systems
Tasman Drive
San Jose, CA 95134
USA

EMail: [email protected]

Stig Venaas
Cisco Systems
Tasman Drive
San Jose, CA 95134
USA

EMail: [email protected]

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