ISO Address

Protocols

ISO Address

ISO network layer addresses are a bit more complex than IP addresses. These addresses are variable length and can be up to 20 octets long. Any packet containing an ISO network layer address must also have a corresponding field with the address' length. The format for an ISO address is displayed in Figure A.5.

Figure A.5: ISO Address Format

The AREA part of the address identifies the level 1 subnetwork or area, and the ID section identifies the station in the area. The AREA portion of an ISO network address actually can be divided into subfields with each specifying a different level subnet in a hierarchical routing scheme. (The notion of areas is discussed in the Routing Protocols section.) The SEL section of the address is used to differentiate different network layer users.

The netWorks application takes a simpler approach to ISO addresses, and its ISO address format is shown in Figure A.6. ISO network addresses are specified in netWorks as three integers, separated by periods.

Figure A.6: netWorks ISO Address Format

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