OSI/TS Configuration and Management Manual

Background Information About Addressing
OSI/TS Configuration and Management Manual—424831-001
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Step 1: Converting to Network Layer Format
Step 1: Converting to Network Layer Format
NSAP addresses first must be converted into a computer-readable format, as follows:
•
AFI, IDI, and decimal-syntax DSP values
Since these values are expressed in decimal digits, they can be easily used as input,
as is.
•
DSP values: binary syntax
Binary-syntax DSP values are represented in hexadecimal (two digits per octet).
•
DSP values: character-based syntax
ISO 646 syntax or national-character syntax DSP values are useful only in a system
having the desired character set in its native mode. Therefore, character-based
syntax is not easily communicated in networks having dissimilar systems or in
networks connecting people of different nationalities. If, however, there is a method
of representing the non-native characters in computer-readable form (using some
conversion process), such DSP values can be used.
Step 2: Encoding Network Layer Protocols
Once NSAP addresses are entered into the system, they are encoded by the Network
Layer protocols and included in NPDUs for transmission. (The encoded NSAP
addresses have a maximum of 20 binary octets.) These protocols use a binary encoding
method called the preferred binary encoding method, defined in ISO 8348, Addendum 2.
The binary encoding is straightforward for the AFI values, the IDI values, and the
decimal -syntax and binary-syntax DSP values. However, DSP values in character-
based syntax must be represented by numeric codes (in decimal or hexadecimal).
The preferred binary encoding method is designed to neutralize any advantages one
character code may have over another. Therefore, a DSP value in ISO 646 syntax, for
example, does not resemble its binary encoded value. For network addressing domains
that use the national character set, the network addressing authority must define and
publish the binary encoding rules to be used by the Network Layer protocols.
Notational Format for Encoded NSAP Addresses
HRPF (hexadecimal reference publication format) is the designated notational format
used in written and verbal communication to convey encoded NSAP addresses. Using
this format, an NSAP address is expressed as a slash (/) followed by a string of
hexadecimal digits (up to 40 maximum), where each digit represents a half-octet of the
encoded address.
How OSI/TS Handles NSAP Addresses
The OSI/TS subsystem uses HRPF without the “/” for all NSAP address parameters in
SCF commands and the application interface. This format enables the OSI/TS
subsystem to handle all NSAP addresses in the same way, regardless of any locally
chosen semantics and syntax.