RFC 1526 (rfc1526) - Page 2 of 8
Assignment of System Identifiers for TUBA/CLNP Hosts
Alternative Format: Original Text Document
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_____|_______________DSP______________| |__AFI_|_IDI_|_____HO-DSP______|___ID___|_SEL_| 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 performance.) 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
