IBM SC30-3865-04 - Manual (Page 318)

GOSIP Version 2 NSAPs
Government Open Systems Interconnection Profile (GOSIP) Version 2 provides for
government use the NSAP addressing format illustrated in Figure 23. The
authorities responsible for the address have clearly defined the fields and specified
the addressing format under the DSP set by the National Institute of Standards and
Technology (NIST).
AFI This 1-octet field has a 47 (hexadecimal) designation. This value signifies
that the address is based on the ICD format and that the DSP uses a
binary syntax.
IDI This 2-octet field has a 0005 (hexadecimal) designation. This value is
assigned to the U.S. Government and the format has been established by
NIST.
VER This 1-octet field has designation of 80 (hexadecimal). This value identifies
the DSP format.
Auth. (Authority)
This 3-octet field identifies the authority that controls the distribution of the
NSAP addresses.
Reserved
This 2-octet field is provided to accommodate future growth.
Domain
This 2-octet field contains the routing domain identifier.
Area This 2-octet field contains the area ID.
Sys. ID
This 6-octet field identifies the system.
Selector
This 1-octet field selects the entity to receive the NPDU.
Multicast Addresses
Multicast addressing is the method that level 1 (L1) and level 2 (L2) ISs use to
distribute link-state updates (LSUs) and hello messages to other systems or LANs.
When an LSU or a hello message is multicast, a group of destination stations
receive the packet. For example, an L1 LSU is multicast only to other L1 ISs. An
Intermediate System Hello (ISH) is multicast only to ESs on the same subnetwork.
You can configure multicast addresses for each subnet with the set subnet
command. Table 59 on page 289 lists the multicast addresses for Ethernet and
Token-Ring LANs.
┌───────────┬─────────────────────────────────────────────────────────────┐
│ IDP │ DSP │
├─────┬─────┼─────┬───────┬──────────┬────────┬──────┬─────────┬──────────┤
│ AFI │ IDI │ Ver │ Auth. │ Reserved │ Domain │ Area │ Sys. ID │ Selector │
│ 47 │ 0005│ 80 │ │ │ (2) │ (2) │ (6) │ (1) │
└─────┴─────┴─────┴───────┴──────────┴────────┴──────┴─────────┴──────────┘
Figure 23. GOSIP Address Format
Using OSI/DECnet V
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