OSI/TS Configuration and Management Manual

Background Information About Addressing
OSI/TS Configuration and Management Manual—424831-001
2-9
IDI Component
•
Significance (or lack thereof) of leading zero digits in the IDI
Possible AFI values are shown in Table 2-1
.
If you have an AFI of 39, for example, you know that ISO DCC is the network
addressing authority governing the domain specified in the IDP, that the DSP syntax is
in binary notation, and that the IDI has no leading zeros.
Note that a local network addressing authority is included in these specifications to
provide for coexistence with proprietary or nonstandard network addressing schemes. It
is assumed that such schemes will eventually migrate to the OSI standard by
encapsulation. Nevertheless, local network addressing schemes are useful during
testing, and can be used for other interim purposes.
IDI Component
The IDI (initial domain identifier) contains information about the domain governed by
the network addressing authority specified in the AFI. The IDI contains a variable-
length sequence of decimal digits, from 0 through 15 digits in length, that specify the
following information:
•
Network addressing domain
•
Network addressing authority responsible for the structure
and assignment of the DSP values
Possible IDI values are shown in Table 2-2
.
Table 2-1. AFI Values
DSP Syntax
Decimal Binary Character
(ISO 646)
National
Character
IDI Format
(Authority)
IDI*
nonzero
IDI*
zero
IDI*
nonzero
IDI*
zero
X.121 36 52 37 53
ISO DCC 38 39
F.69 40 54 41 55
E.163 42 56 43 57
E.164 44 58 45 59
ISO ICD 46 47
Local 48 49 50 51
* First significant digit of variable-length IDI values