AIS AI2524 user manual Understand Addresses, 1NSAP Address Fields

AI2524 Router Card User’s Manual

Understand Addresses

Addresses in the ISO network architecture are referred to as NSAP ad- dresses and network entity titles (NETs). Each node in an OSI network has one or more NETs. In addition, each node has many NSAP ad- dresses. Each NSAP address differs from one of the NETs for that node in only the last byte. This byte is called the N-selector. Its func- tion is similar to the port number in other protocol suites.

The AI2524 router supports all NSAP address formats that are defined by ISO 8348/Ad2; however, the AI2524 router provides ISO IGRP o IS-IS dynamic routing only for NSAP addresses that conform to the address constraints defined in the ISO standard for IS-IS (ISO 10589).

An NSAP address consists of these two major fields, as shown inFig- ure 9-1:

zThe initial domain p art (IDP) is made up of 1-byte authority and format identifier (AFI) and a variable-length initial

domai nidentifier (IDI). The length of the IDI and the encoding format for the domai nspecific part (DSP) are based on the value of the AFI.

zThe DSP is made up of a high-order DSP, an area identifier, a sys- tem identifier, and a 1-byte N-selector (labeled S).

Figure 9-1:NSAP Address Fields

Assign addresses or NETs for your domains and areas. Th

domai naddress uniquely identifies the routing domain. All routers within a given doma inare given the same dom ainaddress. Within each routing domain, you can set up one or more areas, as shown in Figure 9-2. Determine which routers are to be assigned to which areas.

Page 9-2	August 1997
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