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Tech Note #22: Asynchronous Transfer Mode (ATM)  Addresses
©
1998 Bionic Buffalo Corporation; All Rights Reserved.
       14 September 1998
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ICD Format
This format is almost identical to the DCC format. International organizations (as
opposed to individual countries) use this format for address allocation. The DCC field
is replaced by an ICD field. The British Standards Institute maintains values for the
ICDs.
E.164 Format
This format is based on ISDN telephone numbers. Eight octets (64 bits) are used to
specify the number, which can be up to 15 decimal digits long.
ISDN numbers consist of a country code, a national destination code, and a subscriber
number
. Country codes are from one to three digits. Usually, the subscriber number is
the “local” telephone number, and the national destination code is the area code, city
code, or other routing information within the country. Both the subscriber number and
the national destination code may be of any length, as defined by national standards, so
that the total length is no more than 15 digits.
A
F
I
routing
domain
(RD)
area
identi-
fier
(AREA)
end-system identifier
(ESI)
S
E
L
ISDN Adddress (telephone
number)
The other fields may be used for routing, or for specifying sub-addresses within a
destination subscriber’s number.
Internetworking Addresses
When ATM networks are connected to non-ATM networks, there are sometimes formalized
relationships among the different networks’ addressing scheme. In some circumstances, it is
possible to compute all or a portion of one network’s address from the other network’s address.
Because of the complexity of the issues, and the variety of situations, detailed discussion of
these address relationships are beyond the scope of this document.
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