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DTE Address Structure 194

DTE Address Structure

This section describes the structure of the called-DTE and calling-DTE field.

The DTE address structure described here is based on CCITT

Recommendation X.25 (1988). To find out if your network differs from these

specifications, or uses earlier versions of them, refer to your network manager.

DNIC

CCITT Recommendation X.121 defines a general address format which may

be 12, 13, or 14 digits long. The first four digits make up the Data Network

Identification Code (DNIC). The first three digits of the DNIC generally identify

the country—much like area codes—with the exception of large countries such

as the United States. The fourth digit identifies a particular network within that

country.

In Canada, for example, DNICs begin with the digits 302. DATAPAC’s DNIC

is 3020. The DNIC for Infoswitch is 3029.

There is a listing of major public data networks together with their DNICs later

in this chapter.

National Number

Digits 5 through 12 of the DTE address are known as the National Number,

which identifies the DTE within the network. This is an address assigned to a

specific location at the time of subscription.

Some networks support optional sub-addressing for use by the DTE on a per-

call basis. When a sub-address is used, it will pass transparently through the

network and will not be verified by the network. This one- or two-digit number

may be used to address a particular PC on a local area network or a specific

application program within a PC.

Note

The DTE Address format may vary from one network to another. You

should, therefore, verify with your administration to what degree it is

compatible with CCITT recommendations. For example, some networks prefix

an international address with an escape digit: Telecom Canada's DATAPAC

uses prefix 1.

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Eicon Networks C21 Installationsanleitung Seite 194