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rfc:rfc4548

Network Working Group E. Gray Request for Comments: 4548 J. Rutemiller Updates: 1888, 4048 Ericsson Category: Standards Track G. Swallow

                                                   Cisco Systems, Inc.
                                                              May 2006
      Internet Code Point (ICP) Assignments for NSAP Addresses

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 Internet Society (2006).

Abstract

 This document is intended to accomplish two highly inter-related
 tasks: to establish an "initial" Internet Code Point (ICP) assignment
 for each of IPv4 and IPv6 address encoding in Network Service Access
 Point (NSAP) Addresses, and to recommend an IANA assignment policy
 for currently unassigned ICP values.  In the first task, this
 document is a partial replacement for RFC 1888 -- particularly for
 section 6 of RFC 1888.  In the second task, this document
 incorporates wording and specifications from ITU-T Recommendation
 X.213 and further recommends that IANA use the "IETF consensus"
 assignment policy in making future ICP assignments.

Table of Contents

 1. Introduction ....................................................2
    1.1. Conventions ................................................2
    1.2. Acronyms and Terminology ...................................3
 2. IANA Considerations .............................................3
 3. Initial Allocations and Uses ....................................4
    3.1. IPv4 Address Encoding in an NSAPA ..........................4
    3.2. IPv6 Address Encoding in an NSAPA ..........................5
 4. Security Considerations .........................................6
 5. References ......................................................7
    5.1. Normative References .......................................7
    5.2. Informative References .....................................7

Gray, et al. Standards Track [Page 1] RFC 4548 Internet Code Point (ICP) Assignments May 2006

1. Introduction

 Section 6 of RFC 1888 [1888] previously provided for assignment of
 the initial Internet Code Point (ICP) value '0' for encoding an IPv6
 address in a Network Service Access (or Attachment) Point [NSAP]
 address.  RFC 1888 also defined multiple means for restricted
 encoding of an NSAP address in an IPv6 address.
 The means RFC 1888 defined for encoding NSAP addresses in IPv6
 address format was heavily annotated with warnings and limitations
 that apply should this encoding be used.  Possibly as a result, these
 encodings are not used and appear never to have been used in any IPv6
 deployment.  In addition, section 6 contains minor errors.  As a
 result of these various considerations, RFC 1888 [1888] has been
 obsoleted and declared Historic by RFC 4048 [4048].
 It is the belief of the authors of this document that the errors in
 section 6 of RFC 1888 resulted -- at least in part -- because the
 ITU-T specification [X.213] that originally assigned Authority and
 Format Identifier (AFI) '35' to IANA was not freely publicized, nor
 was it incorporated or explained using the mechanism commonly used in
 the IETF, i.e., an RFC.
 It is therefore part of the purpose of this document to provide that
 explanation.
 In addition, because there are other documents that refer to the IPv6
 ICP assignment in RFC 1888, it is necessary for the errors in section
 6 of RFC 1888 to be corrected, irrespective of the RFC's ultimate
 status.
 Finally, no previous RFC (including RFC 1888) has ever formalized an
 assignment of an IPv4 ICP.  This may have been in part because of a
 lack of formal definition of an IANA assignment policy for ICP values
 under the IANA-allocated AFI ('35').
 This document replaces section 6 of RFC 1888 in defining the ICP for
 IPv6 address encoding in an NSAP address, and it formalizes the ICP
 assignment for IPv4 address encoding in an NSAP address.

1.1. Conventions

 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 RFC 2119 [2119].

Gray, et al. Standards Track [Page 2] RFC 4548 Internet Code Point (ICP) Assignments May 2006

1.2. Acronyms and Terminology

 AFI   - Authority and Format Identifier
 BCD   - Binary Coded Decimal
 DSP   - Domain Specific Part
 IANA  - Internet Assigned Numbers Authority
 ICP   - Internet Code Point
 IDI   - Initial Domain Identifier
 IDP   - Initial Domain Part
 IETF  - Internet Engineering Task Force
 ISO   - International Organization for Standardization
 NSAP  - Network Service Access (or Attachment) Point (often NSAPA)
 NSAPA - NSAP Address; 20-Octet Address Format
 OSI   - Open Systems Interconnection
 RFC   - Request For Comments
 WIP   - Work In Progress

2. IANA Considerations

 An ITU-T Recommendation [X.213] has allocated two AFIs designating
 IANA as the assignment authority.  One of these two AFIs ('34') is
 allocated for assignment of NSAPA in Decimal Numeric Format.  This
 document does not address allocation for this AFI as it is not clear
 what use (if any) can be made of this encoding format at this time.
 The other AFI ('35') is to be used for binary encoding except as
 noted below.
 The NSAPA format consists of an Initial Domain Part (IDP) and Domain
 Specific Part (DSP).  The IDP, in turn, consists of an Authority and
 Format Identifier (AFI) and an Initial Domain Identifier (IDI).  The
 AFI is defined to be a binary octet, and the IDI is defined to be a
 four decimal digit number encoded in two octets using Binary Coded
 Decimal format.  Each nibble of the IDI is used to represent a
 decimal digit, using binary value '0000' through '1001'.
 In assigning allocation authority for AFI '35' to IANA, the ITU-T
 Recommendation [X.213] specifies that the two-octet IDI will be used
 to hold an Internet Code Point (ICP) that, because of the decimal
 encoding, MUST be in the decimal range from '0' to '9999'.
 The ITU-T recommendation assumes the assignment of ICP '0' (zero) for
 IPv6 address encoding in a Network Service Access Point Address
 (NSAPA, or often NSAP).  In addition, ITU-T assumed that IANA would
 assign an ICP for IPv4 address encoding in an NSAPA and X.213 assumed
 that the ICP value for this purpose would be '1'.

Gray, et al. Standards Track [Page 3] RFC 4548 Internet Code Point (ICP) Assignments May 2006

 In an NSAPA, the DSP is the remaining octets after the IDP.  For AFI
 '35', this is 17 octets having a format as defined by IANA or as
 defined by another party and published with IANA consent.
 IANA, as the authority responsible for AFI '35', SHOULD NOT assign an
 ICP unless there is a corresponding defined, and published, format at
 the time of the code point assignment.
 The IANA has assigned the following ICP values:
     ICP Value   Address Encoding   Format Definition
     ----------  -----------------  ----------------------------
        '0'           IPv6          RFC 4548, section 3.2
        '1'           IPv4          RFC 4548, section 3.1
 Remaining decimal values '2' through '9999' MUST be assigned on an
 IETF consensus basis [2434].

3. Initial Allocations and Uses

 This document continues the ICP assignment and format definition as
 previously defined in RFC 1888, and it formalizes the allocation of
 ICP value '1' for IPv4 encoding and the format to be used.  The
 sections below describe the specific IPv4 and IPv6 address encoding
 formats.

3.1. IPv4 Address Encoding in an NSAPA

 If it is required, for whatever reason, to embed an IPv4 address
 inside a 20-octet NSAP address, then the following format MUST be
 used.  Note: alignment is an artifact of existing NSAPA usage.
 A specific possible use of this embedding is to express an IP address
 within the ATM Forum address format.  Another possible use would be
 to allow Connectionless Network Protocol (CLNP) packets that
 encapsulate IPv4 packets to be routed in a CLNP network using the
 IPv4 address architecture.  Several leading octets of the IPv4
 address could be used as a CLNP routing prefix.
 An NSAPA with an AFI value of '35' and an ICP value of '1' (one)
 encodes a 4-octet IPv4 address in the first 4 octets of the DSP.  The
 last 13 octets of the DSP are unspecified in this document.  To
 maintain compatibility with both NSAP format and IPv4 addressing,
 these octets MUST be present, but have no intrinsic significance for
 IPv4.  The default values for the unspecified octets is zero.

Gray, et al. Standards Track [Page 4] RFC 4548 Internet Code Point (ICP) Assignments May 2006

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0-3 | AFI = 0x35 | ICP = 0001 | IPv4 (octet 0)|

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4-7 | IPv4 (octets 1-3) | |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

8-11 | |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

12-15| |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

16-19| |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 An NSAPA with the IANA AFI code and ICP set to '1' (one) is converted
 to an IPv4 address by stripping off the first 3 and the last 13
 octets.  If the NSAP-addressed contents are passed to a higher layer,
 the last 13 octets SHOULD be presented to the higher layer as well.
 If an NSAP address using this encoding is used for routing in an IPv4
 routing architecture, only the 4-octet IPv4 address MAY be
 considered.

3.2. IPv6 Address Encoding in an NSAPA

 If it is required, for whatever reason, to embed an IPv6 address
 inside a 20-octet NSAP address, then the following format MUST be
 used.  Note: alignment is an artifact of existing NSAPA usage.
 A specific possible use of this embedding is to express an IP address
 within the ATM Forum address format.  Another possible use would be
 to allow CLNP packets that encapsulate IPv6 packets to be routed in a
 CLNP network using the IPv6 address architecture.  Several leading
 octets of the IPv6 address could be used as a CLNP routing prefix.
 An NSAPA with an AFI value of '35' and an ICP value of '0' (zero)
 encodes a 16-octet IPv6 address in the first 16 octets of the DSP.
 The last octet of the DSP is a selector.  To maintain compatibility
 with both NSAP format and IPv6 addressing, this octet MUST be
 present, but it has no intrinsic significance for IPv6.  Its default
 value is zero, but other values may be used as specified for any
 specific application.  For example, this octet may be used to specify
 one of 255 possible port numbers.

Gray, et al. Standards Track [Page 5] RFC 4548 Internet Code Point (ICP) Assignments May 2006

     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

0-3 | AFI = 0x35 | ICP = 0000 | IPv6 (octet 0)|

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4-7 | IPv6 (octets 1-4) |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

8-11 | IPv6 (octets 5-8) |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

12-15| IPv6 (octets 9-12) |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

16-19| IPv6 (octets 13-15) | |

    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 An NSAPA with the IANA AFI code and ICP set to '0' (zero) is
 converted to an IPv6 address by stripping off the first 3 octets and
 the 20th octet.  If the NSAP-addressed contents are passed to a
 higher layer, the last octet SHOULD be presented to the higher layer
 as well.
 If an NSAP address using this encoding is used for routing in an IPv6
 routing architecture, only the 16-octet IPv6 address MAY be
 considered.

4. Security Considerations

 The NSAP encoding of IPv4 and IPv6 addresses is compatible with the
 corresponding security mechanisms of RFC 4301 [4301], hence this
 document introduces no new security exposure in the Internet.

Gray, et al. Standards Track [Page 6] RFC 4548 Internet Code Point (ICP) Assignments May 2006

5. References

5.1. Normative References

 [4301]  Kent, S. and K. Seo, "Security Architecture for the Internet
         Protocol", RFC 4301, December 2005.
 [2119]  Bradner, S., "Key words for use in RFCs to Indicate
         Requirement Levels", BCP 14, RFC 2119, March 1997.
 [NSAP]  International Organization for Standardization, "Information
         technology - Open Systems Interconnection - Network service
         Definition", ISO/IEC 8348:2002, 2002.
 [X.213] ITU-T Recommendation X.213, X-Series Recommendations, Data
         Networks and Open Systems Communications, October, 2001.
 [2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
         Considerations Section in RFCs", BCP 26, RFC 2434, October
         1998.

5.2. Informative References

 [1888]  Bound, J., Carpenter, B., Harrington, D., Houldsworth, J.,
         and A. Lloyd, "OSI NSAPs and IPv6", RFC 1888, August 1996.
 [4048]  Carpenter, B., "RFC 1888 Is Obsolete", RFC 4048, April 2005.

Gray, et al. Standards Track [Page 7] RFC 4548 Internet Code Point (ICP) Assignments May 2006

Authors' Addresses

 Eric Gray
 Ericsson
 900 Chelmsford Street
 Lowell, MA, 01851
 EMail: Eric.Gray@Marconi.com
 John Rutemiller
 Ericsson
 3000 Marconi Drive
 Warrendale, PA, 15086-7502
 EMail: John.Rutemiller@Marconi.com
 George Swallow
 Cisco Systems, Inc.
 1414 Massachusetts Avenue
 Boxborough, MA, 01719
 EMail: swallow@cisco.com

Gray, et al. Standards Track [Page 8] RFC 4548 Internet Code Point (ICP) Assignments May 2006

Full Copyright Statement

 Copyright (C) The Internet Society (2006).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

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Acknowledgement

 Funding for the RFC Editor function is provided by the IETF
 Administrative Support Activity (IASA).

Gray, et al. Standards Track [Page 9]

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