IP Router Alert Considerations and Usage
RFC 6398

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Internet Engineering Task Force (IETF)               F. Le Faucheur, Ed.
Request for Comments: 6398                                         Cisco
BCP: 168                                                    October 2011
Updates: 2113, 2711
Category: Best Current Practice
ISSN: 2070-1721

                IP Router Alert Considerations and Usage

Abstract

   The IP Router Alert Option is an IP option that alerts transit
   routers to more closely examine the contents of an IP packet.  The
   Resource reSerVation Protocol (RSVP), Pragmatic General Multicast
   (PGM), the Internet Group Management Protocol (IGMP), Multicast
   Listener Discovery (MLD), Multicast Router Discovery (MRD), and
   General Internet Signaling Transport (GIST) are some of the protocols
   that make use of the IP Router Alert Option.  This document discusses
   security aspects and usage guidelines around the use of the current
   IP Router Alert Option, thereby updating RFC 2113 and RFC 2711.
   Specifically, it provides recommendations against using the Router
   Alert in the end-to-end open Internet and identifies controlled
   environments where protocols depending on Router Alert can be used
   safely.  It also provides recommendations about protection approaches
   for service providers.  Finally, it provides brief guidelines for
   Router Alert implementation on routers.

Status of This Memo

   This memo documents an Internet Best Current Practice.

   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
   BCPs 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/rfc6398.

Le Faucheur               Best Current Practice                 [Page 1]
RFC 6398               Router Alert Considerations          October 2011

Copyright Notice

   Copyright (c) 2011 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
   2. Terminology .....................................................4
      2.1. Conventions Used in This Document ..........................4
   3. Security Concerns of Router Alert ...............................5
   4. Guidelines for Use of Router Alert ..............................7
      4.1. Use of Router Alert End to End in the Internet
           (Router Alert in Peer Model) ...............................7
      4.2. Use of Router Alert in Controlled Environments .............9
           4.2.1. Use of Router Alert within an Administrative
                  Domain ..............................................9
           4.2.2. Use of Router Alert in Overlay Model ...............11
      4.3. Router Alert Protection Approaches for Service Providers ..13
   5. Guidelines for Router Alert Implementation .....................15
   6. Security Considerations ........................................16
   7. Contributors ...................................................16
   8. Acknowledgments ................................................16
   9. References .....................................................17
      9.1. Normative References ......................................17
      9.2. Informative References ....................................17

Le Faucheur               Best Current Practice                 [Page 2]
RFC 6398               Router Alert Considerations          October 2011

1.  Introduction

   [RFC2113] and [RFC2711] define the IPv4 and IPv6 Router Alert Options
   (RAOs), respectively.  In this document, we collectively refer to
   those options as the IP Router Alert.  The IP Router Alert Option is
   an IP option that alerts transit routers to more closely examine the
   contents of an IP packet.

   Some of the protocols that make use of the IP Router Alert are the
   Resource reSerVation Protocol (RSVP) ([RFC2205], [RFC3175],
   [RFC3209]), Pragmatic General Multicast (PGM) ([RFC3208]), the
   Internet Group Management Protocol (IGMP) ([RFC3376]), Multicast
   Listener Discovery (MLD) ([RFC2710], [RFC3810]), Multicast Router