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ICMP Extensions for Multiprotocol Label Switching
RFC 4950

Document type: RFC - Proposed Standard (August 2007)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: WG Document
Consensus: Unknown
Document shepherd: No shepherd assigned

IESG State: RFC 4950 (Proposed Standard)
Responsible AD: Ross Callon
Send notices to: mpls-chairs@tools.ietf.org

Network Working Group                                          R. Bonica
Request for Comments: 4950                              Juniper Networks
Category: Standards Track                                         D. Gan
                                                               D. Tappan
                                                              Consultant
                                                            C. Pignataro
                                                     Cisco Systems, Inc.
                                                             August 2007

           ICMP Extensions for Multiprotocol Label Switching

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 Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This memo defines an extension object that can be appended to
   selected multi-part ICMP messages.  This extension permits Label
   Switching Routers to append MPLS information to ICMP messages, and
   has already been widely deployed.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
   2.  Conventions Used in This Document . . . . . . . . . . . . . . . 3
   3.  Application to TRACEROUTE . . . . . . . . . . . . . . . . . . . 3
   4.  Disclaimer  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   5.  MPLS Label Stack Object . . . . . . . . . . . . . . . . . . . . 4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 6

Bonica, et al.              Standards Track                     [Page 1]
RFC 4950                       ICMP MPLS                     August 2007

1.  Introduction

   IP routers use the Internet Control Message Protocol, ICMPv4
   [RFC0792] and ICMPv6 [RFC4443], to convey control information to
   source hosts.  Network operators use this information to diagnose
   routing problems.

   When a router receives an undeliverable IP datagram, it can send an
   ICMP message to the host that originated the datagram.  The ICMP
   message indicates why the datagram could not be delivered.  It also
   contains the IP header and leading payload octets of the "original
   datagram" to which the ICMP message is a response.

   MPLS Label Switching Routers (LSR) also use ICMP to convey control
   information to source hosts.  Section 2.3 of [RFC3032] describes the
   interaction between MPLS and ICMP, and Sections 2.4 and 3 of
   [RFC3032] provide applications of that interaction.

   When an LSR receives an undeliverable MPLS-encapsulated datagram, it
   removes the entire MPLS label stack, exposing the previously
   encapsulated IP datagram.  The LSR then submits the IP datagram to an
   error processing module.  Error processing can include ICMP message
   generation.

   The ICMP message indicates why the original datagram could not be
   delivered.  It also contains the IP header and leading octets of the
   original datagram.

   The ICMP message, however, contains no information regarding the MPLS
   label stack that encapsulated the original datagram when it arrived
   at the LSR.  This omission is significant because the LSR would have
   forwarded the original datagram based upon information contained by
   the MPLS label stack.

   This memo defines an ICMP extension object that permits an LSR to
   append MPLS information to ICMP messages.  Selected ICMP messages
   SHOULD include the MPLS label stack, as it arrived at the router that
   is sending the ICMP message.  The ICMP message MUST also include the
   IP header and leading payload octets of the original datagram.

   The ICMP extensions defined in this document must be preceded by an
   ICMP Extension Structure Header and an ICMP Object Header.  Both are
   defined in [RFC4884].

   The ICMP extension defined in this document is equally applicable to
   ICMPv4 [RFC0792] and ICMPv6 [RFC4443].  Throughout this document,
   unless otherwise specified, the acronym ICMP refers to multi-part
   ICMP messages, encompassing both ICMPv4 and ICMPv6.

Bonica, et al.              Standards Track                     [Page 2]
RFC 4950                       ICMP MPLS                     August 2007

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