OSI/AS Configuration and Management Manual

OSI/AS Configuration and Management Manual—424119-001
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NSAP Addressing
This section provides background information on network service access point (NSAP)
addressing in the lower layers (needed when configuring an OSI/AS subsystem).
This section is intended for anyone who must construct an NSAP address or use an
NSAP address in a command, or who must write an application that uses OSI/AS. If you
are already familiar with how NSAP addresses are constructed and how network
addressing authorities and domains work, then you do not need to read this section.
An NSAP address is the global, network unique address of an end system NSAP.
Correct NSAP addressing, therefore, is crucial to proper network configuration.
However, NSAP addresses can be complicated, and costly mistakes can be made when
configuring them. A thorough understanding of NSAP addressing schemes is
particularly important for customers who are implementing OSI networks in which
Compaq products communicate with products supplied by other vendors.
This section contains the following main topics, which apply to all OSI addresses (in
other words, this is general information that applies to OSI products from all vendors):
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SNPA Addresses on page 3-1
•
LSAP Selectors on page 3-3
•
NSAP Addresses on page 3-4
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Structure of NSAP Addresses on page 3-8
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Converting NSAP Addresses on page 3-13
•
Examples of NSAP Addresses on page 3-14
•
Suggestions for Network Addressing Administrators on page 3-18
SNPA Addresses
An SNPA (subnetwork point of attachment) address is the address of an end system or
intermediate system. It is the address through which subnetwork service is made
available to the Network Layer. What an SNPA address actually means depends on
whether it refers to a LAN or an X.25 WAN, as discussed in the following subsections:
•
SNPA Addresses Over LANs on this page
•
SNPA Addresses Over X.25 WANs on page 3-3
SNPA Addresses Over LANs
In a LAN environment, the SNPA address is the fixed hexadecimal string FE followed
by the MAC (media access control) address of the LAN controller. The MAC address is
assigned and hardwired into the controller by the manufacturer. Note that due to the lack
of a common, formal definition for SNPA addresses, other OSI implementations may
interpret the SNPA address as the MAC address only. Such implementations, however,
do not cause any interoperation problem with the way SNPA addresses are used in the
protocols.
In D-series OSI/AS subsystems that use TLAM to provide subnetwork services, the
SNPA address of the TSP process is described as follows: