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rfc:rfc5350

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             |
 +----------+-------------------------+------------------------------+
 | 0        | Router shall examine    | Datagram contains a          |
 |          | packet [RFC2113]        | Multicast Listener Discovery |
 |          | [RFC2205] [RFC3376]     | message [RFC2711] [RFC2710]  |
 |          | [RFC4286]               | [RFC4286]                    |
 | 1        | Aggregated Reservation  | Datagram contains RSVP       |
 |          | Nesting Level 1         | message [RFC2711] [RFC2205]  |
 |          | [RFC3175]               |                              |
 | 2        | Aggregated Reservation  | Datagram contains an Active  |
 |          | Nesting Level 2         | Networks message [RFC2711]   |
 |          | [RFC3175]               | [Schwartz2000]               |
 | 3        | Aggregated Reservation  | Aggregated Reservation       |
 |          | Nesting Level 3         | Nesting Level 0 [RFC3175](*) |
 |          | [RFC3175]               |                              |
 | 4        | Aggregated Reservation  | Aggregated Reservation       |
 |          | Nesting Level 4         | Nesting Level 1 [RFC3175]    |
 |          | [RFC3175]               |                              |
 | 5        | Aggregated Reservation  | Aggregated Reservation       |
 |          | Nesting Level 5         | Nesting Level 2 [RFC3175]    |
 |          | [RFC3175]               |                              |
 | ...      | ...                     | ...                          |
 | 32       | Aggregated Reservation  | Aggregated Reservation       |
 |          | Nesting Level 32        | Nesting Level 29 [RFC3175]   |
 |          | [RFC3175]               |                              |
 | 33       | Reserved                | Aggregated Reservation       |
 |          |                         | Nesting Level 30 [RFC3175]   |
 | 34       | Reserved                | Aggregated Reservation       |
 |          |                         | Nesting Level 31 [RFC3175]   |
 | 35       | Reserved                | Aggregated Reservation       |
 |          |                         | Nesting Level 32(*)          |
 |          |                         | [RFC3175]                    |
 | 36-65534 | Reserved                | Reserved to IANA for future  |
 |          |                         | assignment                   |
 | 65535    | Reserved                | Reserved [IANA-IPv6RAO]      |
 +----------+-------------------------+------------------------------+
 Note (*): The entry in the above table for the IPv6 RAO Value of 35
 (Aggregated Reservation Nesting Level 32) has been marked due to an
 inconsistency in the text of [RFC3175], and is consequently reflected

Manner & McDonald Standards Track [Page 3] RFC 5350 IANA Considerations for Router Alert September 2008

 in the IANA registry.  In that document, the values 3-35 (i.e., 33
 values) are defined for nesting levels 0-31 (i.e., 32 levels).
 Similarly, value 3 is a duplicate, because aggregation level 0 means
 end-to-end signaling, and this already has an IPv6 RAO value "1"
 assigned.
 Also note that nesting levels begin at 1 for IPv4 (described in
 Section 1.4.9 of [RFC3175]) and 0 for IPv6 (allocated in Section 6 of
 [RFC3175]).
 Section 3.2 of this document redefines these so that for IPv6, value
 3 is no longer used and values 4-35 represent levels 1-32.  This
 removes the above inconsistencies.

3. IANA Considerations

 This section contains the new procedures for managing IPv4 Router
 Alert Option Values.  IANA has created a registry for IPv4 Router
 Alert Option Values (described in Section 3.1) and has updated the
 IPv6 Router Alert Option Values (described in Section 3.2).
 IP Router Alert Option Values are currently managed separately for
 IPv4 and IPv6.  This document does not change this, as there is
 little value in forcing the two registries to be aligned.

3.1. IANA Considerations for IPv4 Router Alert Option Values

 The Value field, as specified in [RFC2113], is two octets in length.
 The Value field is registered and maintained by IANA.  The initial
 contents of this registry are:
 +-------------+--------------------------------------+-----------+
 | Value       | Description                          | Reference |
 +-------------+--------------------------------------+-----------+
 | 0           | Router shall examine packet          | [RFC2113] |
 | 1-32        | Aggregated Reservation Nesting Level | [RFC3175] |
 | 33-65502    | Available for assignment by the IANA |           |
 | 65503-65534 | Available for experimental use       |           |
 | 65535       | Reserved                             |           |
 +-------------+--------------------------------------+-----------+
 New values are to be assigned via IETF Review as defined in
 [RFC5226].

Manner & McDonald Standards Track [Page 4] RFC 5350 IANA Considerations for Router Alert September 2008

3.2. IANA Considerations for IPv6 Router Alert Option Values

 The registry for IPv6 Router Alert Option Values continues to be
 maintained as specified in [RFC2711].  In addition, the following
 value has been removed from the IANA registry and reserved for
 possible future use (not to be allocated currently).  The reason is
 that it is a duplicate value; aggregation level 0 means end-to-end
 signaling, and this already has an IPv6 RAO value "1" assigned.
 +-------+--------------------------+-----------+
 | Value | Description              | Reference |
 +-------+--------------------------+-----------+
 | 3     | RSVP Aggregation level 0 | [RFC3175] |
 +-------+--------------------------+-----------+
 The following IPv6 RAO values are available for experimental use:
 +-------------+------------------+-----------+
 | Value       | Description      | Reference |
 +-------------+------------------+-----------+
 | 65503-65534 | Experimental use |           |
 +-------------+------------------+-----------+

4. Security Considerations

 Since this document is only concerned with the IANA management of the
 IPv4 and IPv6 Router Alert Option Values registry, it raises no new
 security issues beyond those identified in [RFC2113] and [RFC2711].
 Yet, as discussed in RFC 4727 [RFC4727], production networks do not
 necessarily support the use of experimental code points in IP option
 headers.  The network scope of support for experimental values should
 be evaluated carefully before deploying any experimental RAO value
 across extended network domains, such as the public Internet.  The
 potential to disrupt the stable operation of the network hosting the
 experiment through the use of unsupported experimental code points is
 a serious consideration when planning an experiment using such code
 points.
 When experimental RAO values are deployed within an administratively
 self-contained network domain, the network administrators should
 ensure that each value is used consistently to avoid interference
 between experiments.  When experimental values are used in traffic
 that crosses multiple administrative domains, the experimenters
 should assume that there is a risk that the same values will be used
 simultaneously by other experiments, and thus that there is a

Manner & McDonald Standards Track [Page 5] RFC 5350 IANA Considerations for Router Alert September 2008

 possibility that the experiments will interfere.  Particular
 attention should be given to security threats that such interference
 might create.

5. Acknowledgements

 Thanks to Robert Hancock, Martin Stiemerling, Alan Ford, and Francois
 Le Faucheur for their helpful comments on this document.

6. References

6.1. Normative References

 [RFC2113]        Katz, D., "IP Router Alert Option", RFC 2113,
                  February 1997.
 [RFC2711]        Partridge, C. and A. Jackson, "IPv6 Router Alert
                  Option", RFC 2711, October 1999.
 [RFC3175]        Baker, F., Iturralde, C., Le Faucheur, F., and B.
                  Davie, "Aggregation of RSVP for IPv4 and IPv6
                  Reservations", RFC 3175, September 2001.
 [RFC5226]        Narten, T. and H. Alvestrand, "Guidelines for
                  Writing an IANA Considerations Section in RFCs", BCP
                  26, RFC 5226, May 2008.

6.2. Informative References

 [IANA-IPv6RAO]  "IANA Registry for Internet Protocol version 6 (IPv6)
                  Router Alert Option Values", <http://www.iana.org>.
 [RFC2205]        Braden, R., Ed., Zhang, L., Berson, S., Herzog, S.,
                  and S. Jamin, "Resource ReSerVation Protocol (RSVP)
                  -- Version 1 Functional Specification", RFC 2205,
                  September 1997.
 [RFC2710]        Deering, S., Fenner, W., and B. Haberman, "Multicast
                  Listener Discovery (MLD) for IPv6", RFC 2710,
                  October 1999.
 [RFC3376]        Cain, B., Deering, S., Kouvelas, I., Fenner, B., and
                  A. Thyagarajan, "Internet Group Management Protocol,
                  Version 3", RFC 3376, October 2002.
 [RFC4286]        Haberman, B. and J. Martin, "Multicast Router
                  Discovery", RFC 4286, December 2005.

Manner & McDonald Standards Track [Page 6] RFC 5350 IANA Considerations for Router Alert September 2008

 [RFC4727]        Fenner, B., "Experimental Values In IPv4, IPv6,
                  ICMPv4, ICMPv6, UDP, and TCP Headers", RFC 4727,
                  November 2006.
 [Schwartz2000]   Schwartz, B., Jackson, A., Strayer, W., Zhou, W.,
                  Rockwell, D., and C. Partridge, "Smart Packets:
                  Applying Active Networks to Network Management", ACM
                  Transactions on Computer Systems (TOCS), Volume 18,
                  Issue 1, February 2000.

Authors' Addresses

 Jukka Manner
 Department of Communications and Networking (Comnet)
 Helsinki University of Technology (TKK)
 P.O. Box 3000
 Espoo  FIN-02015 TKK
 Finland
 Phone: +358 9 451 2481
 EMail: jukka.manner@tkk.fi
 Andrew McDonald
 Roke Manor Research Ltd (a Siemens company)
 Old Salisbury Lane
 Romsey, Hampshire  SO51 0ZN
 United Kingdom
 EMail: andrew.mcdonald@roke.co.uk

Manner & McDonald Standards Track [Page 7] RFC 5350 IANA Considerations for Router Alert September 2008

Full Copyright Statement

 Copyright (C) The IETF Trust (2008).
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 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
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Manner & McDonald Standards Track [Page 8]

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