ATM Option System Reference - Comtech EF Data

1.2.7 ATM Addressing
Product Overview
ATM addresses are used to uniquely identify an end system. These addresses identify the
source and destination nodes when establishing SVCs. An end system can have multiple
addresses or accept multiple calls on the same address.
Types of Addresses
The ATM Forum defines two different types of addressing:
• Public networks use E.164 addresses. These addresses can be up to 15 digits
long (8 bytes), and look much like telephone numbers. While E.164 addresses
have a familiar format, they are not practical for private networks. Each address
must be assigned by the carrier, which can get both cumbersome and expensive.
• Private ATM networks use an addressing structure called ATM End System
Address (AESA) that uses a 40-digit address (20 bytes). Several types of AESA
addresses are available:
- DCC format: Includes a Data Country Code (DCC) in the prefix. The DCC
specifies the country in which the address is registered, and is nationally
assigned.
- ICD format: Includes an International Country Designator (ICD) in the prefix.
The ICD identifies an international organization, assigned by the British
Standards Institute.
NOTE: The only difference between DCC and ICD formats is the scope of the organization
that delivers the country code.
- Imbedded E.164 format: Includes an E.164 address in the AESA prefix.
This format is useful when an end system on a private network has to reach an
end system on a public network.
- Local AFI format: Includes only the Authority and Format Identifier (AFI)
in the prefix. This format can be used for an isolated ATM network or when
creating a network for internal purposes only.
Caution: Local AFI addresses must not be used if the ATM
network connects to a public network, since there is no way to
ensure the global uniqueness of these addresses.
All four AESA address formats contain the following:
• AFI: Authority and Format Identifier. This field indicates the format of the
address (ICD, DCC, E.164 AESA or Local AFI).
• DSP: Domain Specific Part, which is further divided into high order (HO-DSP)
and low order (ESI and SEL) fields.
- HO-DSP: High Order Domain Specific Part. The coding of this field is identified
by the same authority that assigned the AESA address.
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