IANA Considerations for the IPv4 and IPv6 Router Alert Options
RFC 5350

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Network Working Group                                          J. Manner
Request for Comments: 5350                                           TKK
Updates: 2113, 3175                                          A. McDonald
Category: Standards Track                                   Siemens/Roke
                                                          September 2008

     IANA Considerations for the IPv4 and IPv6 Router Alert Options

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 (2008).

Abstract

   This document updates the IANA allocation rules and registry of IPv4
   and IPv6 Router Alert Option Values.

Table of Contents

   1. Introduction ....................................................2
   2. Use of the Router Alert Option Value Field ......................2
   3. IANA Considerations .............................................4
      3.1. IANA Considerations for IPv4 Router Alert Option Values ....4
      3.2. IANA Considerations for IPv6 Router Alert Option Values ....5
   4. Security Considerations .........................................5
   5. Acknowledgements ................................................6
   6. References ......................................................6
      6.1. Normative References .......................................6
      6.2. Informative References .....................................6

Manner & McDonald           Standards Track                     [Page 1]
RFC 5350          IANA Considerations for Router Alert    September 2008

1.  Introduction

   The IP Router Alert Option is defined for IPv4 in [RFC2113].  A
   similar IPv6 option is defined in [RFC2711].  When one of these
   options is present in an IP datagram, it indicates that the contents
   of the datagram may be interesting to routers.  The Router Alert
   Option (RAO) is used by protocols such as the Resource Reservation
   Protocol (RSVP) [RFC2205] and IGMP [RFC3376].

   Both the IPv4 and IPv6 options contain a two-octet Value field to
   carry extra information.  This information can be used, for example,
   by routers to determine whether or not the packet should be more
   closely examined by them.

   There can be up to 65536 values for the RAO.  Yet, currently there is
   only a registry for IPv6 values.  No registry or allocation policies
   are defined for IPv4.

   This document updates the IANA registry for managing IPv4 and IPv6
   Router Alert Option Values, and removes one existing IPv6 Router
   Alert Option Value.

2.  Use of the Router Alert Option Value Field

   One difference between the specifications for the IPv4 and IPv6
   Router Alert Options is the way values for the Value field are
   managed.  In [RFC2113], the IPv4 Router Alert Option Value field has
   the value 0 assigned to "Router shall examine packet".  All other
   values (1-65535) are reserved.  Neither a management mechanism (e.g.,
   an IANA registry) nor an allocation policy are provided for the IPv4
   RAO values.

   The IPv6 Router Alert Option has an IANA-managed registry
   [IANA-IPv6RAO] containing allocations for the Value field.

   In [RFC3175], the IPv4 Router Alert Option Value is described as a
   parameter that provides "additional information" to the router in
   making its interception decision, rather than as a registry managed
   by IANA.  As such, this aggregation mechanism makes use of the Value
   field to carry the reservation aggregation level.  For the IPv6
   option, IANA has assigned a set of 32 values to indicate reservation
   levels.  However, since other registrations have already been made in
   that registry, these values are from 3-35 (which is actually a set of
   33 values).

   Although it might have been desirable to have the same values used in
   both the IPv4 and IPv6 registries, the initial allocations in
   [RFC2711] and the aggregation-level allocations in [RFC3175] have

Manner & McDonald           Standards Track                     [Page 2]
RFC 5350          IANA Considerations for Router Alert    September 2008

   made this impossible.  The following table shows the allocations in
   the IPv6 registry and the values used in the IPv4 registry, where the
   latter have been deduced from [RFC2113] and [RFC3175] with the
   assumption that the number of aggregation levels can be limited to 32
   as in the IPv6 case.  Entries for values 6 to 31 have been elided for
   brevity.

   +----------+-------------------------+------------------------------+
   | Value    | IPv4 RAO Meaning        | IPv6 RAO Meaning             |
   +----------+-------------------------+------------------------------+