Internet Engineering Task Force (IETF)
Request for Comments: 6328
BCP: 164
Category: Best Current Practice
ISSN: 2070-1721
D. Eastlake 3rd
July 2011

IANA Considerations for Network Layer Protocol Identifiers


Some protocols being developed or extended by the IETF make use of the ISO/IEC (International Organization for Standardization / International Electrotechnical Commission) Network Layer Protocol Identifier (NLPID). This document provides NLPID IANA considerations.

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

Copyright Notice

Copyright © 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 ( 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 ....................................................2
   2. NLPIDs ..........................................................3
      2.1. Sub-Ranges of the NLPID ....................................3
      2.2. Code Point 0x80 ............................................4
      2.3. NLPIDs Available for IANA Allocation .......................4
   3. IANA Considerations .............................................5
   4. Security Considerations .........................................5
   5. References ......................................................5
      5.1. Normative References .......................................5
      5.2. Informative References .....................................6
   6. Acknowledgements ................................................7
   Appendix A. Initial IANA NLPID Web Page ............................8
   Appendix B. RFC References to NLPID ................................9

1. Introduction

Some protocols being developed or extended by the IETF make use of the ISO/IEC (International Organization for Standardization / International Electrotechnical Commission) Network Layer Protocol Identifier (NLPID).

The term "NLPID" is not actually used in [ISO9577], which refers to one-octet IPIs (Initial Protocol Identifiers) and SPIs (Subsequent Protocol Identifiers). While these are two logically separate kinds of one-octet identifiers, most values are usable as both an IPI and an SPI. In the remainder of this document, the term NLPID is used for such values.

The registry of NLPID values is maintained by ISO/IEC by updating [ISO9577]. The procedure specified by ISO/IEC in that document is that an NLPID code point can be allocated without approval by ISO/IEC, as long as the code point is not in a range of values categorized for an organization other than the organization allocating the code point and as long as ISO/IEC JTC1 SC6 is informed.

This document provides NLPID IANA considerations. That is, it specifies the level of IETF approval necessary for a code point to be allocated for IETF use, the procedures to be used and actions to be taken by IANA in connection with NLPIDs, and related guidelines.

[RFC5226] is incorporated herein except to the extent that there are contrary provisions in this document.

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 [RFC2119].


[ISO9577] defines one-octet network layer protocol identifiers that are commonly called NLPIDs, which is the term used in this document.

NLPIDs are used in a number of protocols. For example, in the mar$pro.type field of the multicast address resolution server protocol [RFC2022], the ar$pro.type field of the NBMA (Non-Broadcast Multi-Access) next hop resolution protocol [RFC2332] and in the IS-IS Protocols Supported TLV [RFC1195]. See Appendix B.

2.1. Sub-Ranges of the NLPID

Sub-ranges of the possible NLPID values are categorized by [ISO9577] for organizations as shown below, primarily for the ISO/IEC (International Organization for Standardization / International Electrotechnical Commission) and the ITU-T (International Telecommunication Union - Telecommunication Standardization Sector):

      Code Point  Category
      ----------  --------
      0x00        ISO/IEC
      0x01-0x0F   ITU-T
      0x10-0x3F   ITU-T Rec. X.25 and ISO/IEC 8208
      0x40-0x43   ISO/IEC
      0x44        ITU-T
      0x45-0x4F   ISO/IEC
      0x50-0x6F   ITU-T Rec. X.25 and ISO/IEC 8208
      0x70-0x7F   Joint ITU-T and ISO/IEC
      0x80        ISO/IEC (see Section 2.2)
      0x81-0x8F   ISO/IEC
      0x90-0xAF   ITU-T Rec. X.25 and ISO/IEC 8208
      0xB0-0xBF   ITU-T
      0xC0-0xCF   Potentially available for IANA (see Section 2.3)
      0xD0-0xEF   ITU-T Rec. X.25 and ISO/IEC 8208
      0xF0-0xFE   Joint ITU-T and ISO/IEC
      0xFF        Reserved for an Extension mechanism to be
                  jointly developed by ITU-T and ISO/IEC

2.2. Code Point 0x80

NLPID 0x80 is known as the IEEE (Institute of Electrical & Electronics Engineers) SNAP (SubNetwork Access Protocol) code point. It is followed by five octets, using the IEEE SNAP SAP (Service Access Point) conventions, to specify the protocol. Those conventions are described in Section 3 of [RFC5342]. In particular, it is valid for such a five-octet sequence to start with the IANA OUI (Organizationally Unique Identifier) followed by two further octets assigned by IANA as provided in [RFC5342]. The same IANA registry is used for such protocol identifiers whether they are planned to be introduced by the 0x80 NLPID or the IEEE SNAP SAP LSAPs (Link-Layer Service Access Points) (0xAAAA). Values allocated by IANA may be used in either context as appropriate.

Because of the limited number of NLPID code points available for IANA allocation, use of the IEEE SNAP NLPID is RECOMMENDED rather than allocation of a new one-octet NLPID code point.

2.3. NLPIDs Available for IANA Allocation

A limited number of code points are available that could be allocated by IANA under [ISO9577]. Because of this, it is desirable, where practical, to use code point 0x80, as discussed in Section 2.2 above, or to get code points allocated from the ranges categorized to other organizations. For example, code point 0x8E was allocated for IPv6 [RFC2460], although it is in a range of code points categorized for ISO/IEC. One-byte code points are assigned to TRILL and IEEE 802.1aq as they are intended for use within the IS-IS Protocols Supported TLV [RFC1195].

The table below, which includes two new code point allocations made by this document, shows those still available.

      Code Point  Status
      ----------  --------
      0xC0        TRILL [RFC6325]
      0xC1        IEEE 802.1aq [802.1aq]
      0xC2-0xCB   Available
      0xCC        IPv4 [RFC791]
      0xCD-0xCE   Available
      0xCF        PPP [RFC1661]

3. IANA Considerations

As long as code points are available, IANA will allocate additional values when required by applying the IETF Review policy as per [RFC5226].

Whenever it allocates an NLPID, IANA will inform the IETF liaison to ISO/IEC JTC1 SC6 (Joint Technical Committee 1, Study Committee 6) [JTC1SC6], or if IANA is unable to determine that IETF liaison, the IAB. The liaison (or the IAB) will then ensure that ISO/IEC JTC1 SC6 is informed so that [ISO9577] can be updated since ISO/IEC JTC1 SC6 is the body that maintains [ISO9577]. To simplify this process, it is desirable that the IAB maintain an IETF liaison to ISO/IEC JTC1 SC6.

This document allocates the code points 0xC0 and 0xC1 as shown in Section 2.3 and IANA shall request the liaison (or the IAB) to so inform ISO/IEC JTC1 SC6.

IANA maintains a web page showing NLPIDs that have been allocated to a protocol being developed or extended by the IETF or are otherwise of interest. The initial state of the web page is as shown in Appendix A. IANA will update this web page for (1) NLPIDs allocated by IANA and (2) other allocations or de-allocations when IANA is requested to make such changes to this web page by the IETF liaison mentioned above.

4. Security Considerations

This document is concerned with allocation of NLPIDs. It is not directly concerned with security.

5. References

5.1. Normative References

[ISO9577] International Organization for Standardization "Information

technology - Telecommunications and Information exchange between systems - Protocol identification in the network layer", ISO/IEC TR 9577:1999, 1999-12-15.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.
   [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
             IANA Considerations Section in RFCs", BCP 26, RFC 5226, May
   [RFC5342] Eastlake 3rd., D., "IANA Considerations and IETF Protocol
             Usage for IEEE 802 Parameters", BCP 141, RFC 5342,
             September 2008.

[RFC6325] Radia, P., Eastlake, D., Dutt, D., Gai, S., and A.

Ghanwani, "RBridges: Base Protocol Specification", RFC 6325, July 2011.

5.2. Informative References

[802.1aq] Standard for Local and Metropolitan Area Networks / Virtual

Bridged Local Area Networks / Amendment 9: Shortest Path Bridging, Draft IEEE P802.1aq/D2.1, 21 August 2009.

   [JTC1SC6] ISO/IEC JTC1 SC6 (International Organization for
             Standardization / International Electrotechnical
             Commission, Joint Technical Committee 1, Study Committee
   [RFC791]  Postel, J., "Internet Protocol", STD 5, RFC 791, September
   [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
             dual environments", RFC 1195, December 1990.
   [RFC1661] Simpson, W., Ed., "The Point-to-Point Protocol (PPP)", STD
             51, RFC 1661, July 1994.
   [RFC1707] McGovern, M. and R. Ullmann, "CATNIP: Common Architecture
             for the Internet", RFC 1707, October 1994.
   [RFC2022] Armitage, G., "Support for Multicast over UNI 3.0/3.1 based
             ATM Networks", RFC 2022, November 1996.

[RFC2332] Luciani, J., Katz, D., Piscitello, D., Cole, B., and N.

Doraswamy, "NBMA Next Hop Resolution Protocol (NHRP)", RFC 2332, April 1998.

   [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
             (IPv6) Specification", RFC 2460, December 1998.

6. Acknowledgements

The contributions and support of the following people, listed in alphabetic order, are gratefully acknowledged:

Ayan Banerjee, Gonzalo Camarillo, Dinesh Dutt, Don Fedyk, Alfred Hines, Russ Housley, Andrew Malis, Radia Perlman, Dan Romascanu, and Peter Ashwood-Smith.

Appendix A. Initial IANA NLPID Web Page

   NLPIDs of Interest
      Code Point  Use
      ----------  --------
       0x00       Null
       0x08       Q.933 (RFC 2427)
       0x80       IEEE SNAP (RFC 6328)
       0x81       ISO CLNP (Connectionless Network Protocol)
       0x82       ISO ES-IS
       0x83       IS-IS (RFC 1195)
       0x8E       IPv6 (RFC 2460)
       0xB0       FRF.9 (RFC 2427)
       0xB1       FRF.12 (RF C2427)
       0xC0       TRILL (RFC 6325)
       0xC1       IEEE 802.1aq
       0xCC       IPv4 (RFC 791)
       0xCF       PPP (RFC 1661)

Note: According to [RFC1707], NLPID 0x70 was assigned to IPv7. That assignment appears to no longer be in effect as it is not listed in ISO/IEC 9577. IPv7 was itself a temporary code point assignment made while a decision was being made between three candidates for the next generation of IP after IPv4. Those candidates were assigned IPv6, IPv7, and IPv8. IPv6 was selected.

Appendix B. RFC References to NLPID

The following RFCs, issued before the end of March 2009, excluding other survey RFCs and obsolete RFCs, reference the NLPID as such:

   RFC 1195  Use of OSI IS-IS for Routing in TCP/IP and Dual
   RFC 1356  Multiprotocol Interconnect on X.25 and ISDN in the Packet
   RFC 1377  The PPP OSI Network Layer Control Protocol (OSINLCP)
   RFC 1661  The Point-to-Point Protocol (PPP)
   RFC 1707  CATNIP: Common Architecture for the Internet
   RFC 1755  ATM Signaling Support for IP over ATM
   RFC 2022  Support for Multicast over UNI 3.0/3.1 based ATM Networks
   RFC 2332  NBMA Next Hop Resolution Protocol (NHRP)
   RFC 2337  Intra-LIS IP multicast among routers over ATM using Sparse
               Mode PIM
   RFC 2363  PPP Over FUNI
   RFC 2390  Inverse Address Resolution Protocol
   RFC 2427  Multiprotocol Interconnect over Frame Relay
   RFC 2590  Transmission of IPv6 Packets over Frame Relay Networks
   RFC 2684  Multiprotocol Encapsulation over ATM Adaptation Layer 5
   RFC 2955  Definitions of Managed Objects for Monitoring and
               Controlling the Frame Relay/ATM PVC Service Interworking
   RFC 3070  Layer Two Tunneling Protocol (L2TP) over Frame Relay
   RFC 5308  Routing IPv6 with IS-IS

Author's Address

Donald E. Eastlake 3rd
Huawei Technologies
155 Beaver Street
Milford, MA 01757 USA

   Phone: +1-508-333-2270