OSI/TS Configuration and Management Manual

Background Information About Addressing
OSI/TS Configuration and Management Manual—424831-001
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X.25 1980 Versus 1984 Addressing
A single network addressing authority can govern one or more domains. However, for
any domain within the domain hierarchy, there must be only one authority that governs
that domain and its subdomains. For example, the domains shown in Figure 2-1
must
not intersect. One domain can wholly encompass another domain, but cannot intersect
to include only a part of another domain.
X.25 1980 Versus 1984 Addressing
There are two different sets of standards that govern Network Layer addressing for X.25
networks: 1980 address standards and 1984 extended address standards, as follows:
X25AM supports extended addresses (1984 addressing standards) for the following
types of packets:
Call request
Incoming call
Call accepted
Call connected
Extended called addresses are not used in clear request packets, and are ignored in clear
indication packets.
Figure 2-2. NSAP Network Addressing Domain Hierarchy
1980 address format: DTE address only (15 decimal digits)
1984 address format: DTE address
+ address extension (up to 40 hexadecimal digits)
+ address extension type (types are: full NSAP, partial NSAP,
non-OSI, reserved)
202CDT .CDD
Global Network
Addressing Domain
Subdomain 2Subdomain 1
System
(NSAP Address)
Subsubdomain
System
(NSAP Address)
System
(NSAP Address)
Subdomain 3
System
(NSAP Address)
Subdomain 4
System
(NSAP Address)