Installing and Administering OSI Transport Services

52 Chapter 1
HP OTS/9000 Resources
Structure of NSAP Addresses
Reserved field - This is simply a portion of the PAP that is not in use,
but has been reserved in case it is needed some time in the future. If the
network administrator defines a PAP with a reserved field, a default
value (usually all 00s) should be defined that the reserved field is always
set to.
NSAP selector - A one octet field at the rightmost portion of the PAP. It
identifies the entity attached to the network layer. In OTS the entity is
always the transport protocol. HP recommends that the NSAP selector
be set to 01.
The section on current allocation formats, and the section on
recommended PAP structures show examples of how these fields are
used to manage NSAP spaces and routing topologies.
ISO IS-IS Routing protocol - ISO is in the process of defining a
protocol standard for a dynamic Intermediate System to Intermediate
System routing protocol, known as the IS-IS protocol. This protocol,
when complete, will allow Intermediate Systems (the ISO term for
network layer routers) to automatically route traffic between each other
across concatenated subnetworks and areas. It will not, however,
automate routing traffic between routing domains. This will still require
static configuration of route information.
Though the protocol is still in development, ISO has defined a format for
the rightmost portion of the DSP to be used by the IS-IS protocol for its
automated routing. Network administrators should use this format
whenever possible so that it is easier to support the IS-IS protocol once it
becomes available.
The format defined by ISO is the following:
Figure 1-11
Area
User
AP
PAP
length (octets)
up to 20 octets
2
Defined
ID
ES
ID
NSel
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