Assignment of System Identifiers for TUBA/CLNP Hosts
RFC 1526

Document Type RFC - Informational (September 1993; No errata)
Last updated 2013-03-02
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Network Working Group                                      D. Piscitello
Request for Comments: 1526                                      Bellcore
Category: Informational                                   September 1993

          Assignment of System Identifiers for TUBA/CLNP Hosts

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard.  Distribution of this memo is


   This document describes conventions whereby the system identifier
   portion of an RFC 1237 style NSAP address may be guaranteed
   uniqueness within a routing domain for the purpose of
   autoconfiguration in TUBA/CLNP internets. The mechanism is extensible
   and can provide a basis for assigning system identifiers in a
   globally unique fashion.


   This memo specifies methods for assigning a 6 octet system identifier
   portion of the OSI NSAP address formats described in "Guidelines for
   OSI NSAP Allocation in the Internet" [1], in a fashion that ensures
   that the ID is unique within a routing domain. It also recommends
   methods for assigning system identifiers having lengths other than 6
   octets. The 6 octet system identifiers recommended in this RFC are
   assigned from 2 globally administered spaces (IEEE 802 or "Ethernet",
   and IP numbers, administered by the Internet Assigned Numbers
   Authority, IANA).

   At this time, the primary purpose for assuring uniqueness of system
   identifiers is to aid in autoconfiguration of NSAP addresses in
   TUBA/CLNP internets [2]. The guidelines in this paper also establish
   an initial framework within which globally unique system identifiers,
   also called endpoint identifiers, may be assigned.


   Many thanks to Radia Perlman, Allison Mankin, and Ross Callon of for
   their insights and assistance. Thanks also to the Ethernet connector
   to my MAC, which conveniently and quite inobtrusively fell out,
   enabling me to get an entire day's worth of work done without email

Piscitello                                                      [Page 1]
RFC 1526              System Identifiers for TUBA         September 1993

1.  Background

   The general format of OSI network service access point (NSAP)
   addresses is illustrated in Figure 1.


                IDP     Initial Domain Part
                AFI     Authority and Format Identifier
                IDI     Initial Domain Identifier
                DSP     Domain Specific Part
                HO-DSP  High-order DSP
                ID      System Identifier
                SEL     NSAP Selector

                Figure 1: OSI NSAP Address Structure.

   The recommended encoding and allocation of NSAP addresses in the
   Internet is specified in RFC 1237. RFC 1237 makes the following
   statements regarding the system identifier (ID) field of the NSAPA:

  1.  the ID field may be from one to eight octets in length

  2.  the ID must have a single known length in any particular
      routing domain

  3.  the ID field must be unique within an area for ESs and
      level 1 ISs, and unique within the routing domain for level
      2 ISs.

  4.  the ID field is assumed to be flat

   RFC 1237 further indicates that, within a routing domain that
   conforms to the OSI intradomain routing protocol [3] the lower-order
   octets of the NSAP should be structured as the ID and SEL fields
   shown in Figure 1 to take full advantage of intradomain IS-IS
   routing. (End systems with addresses which do not conform may require
   additional manual configuration and be subject to inferior routing

   Both GOSIP Version 2 (under DFI-80h, see Figure 2a) and ANSI DCC NSAP
   addressing (Figure 2b) define a common DSP structure in which the
   system identifier is assumed to be a fixed length of 6 octets.

Piscitello                                                      [Page 2]
RFC 1526              System Identifiers for TUBA         September 1993

        octets |_1__|___2____|_1__|_3_|__2__|_2__|_2___|_6_|_1__|

                    Figure 2 (a): GOSIP Version 2 NSAP structure.
        octets |_1__|___2___|_1__|__3__|_2___|_2_|__2__|_6__|_1__|

                     IDP   Initial Domain Part
                     AFI   Authority and Format Identifier
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