ATM Option System Reference - Comtech EF Data

ATM Option
1.2.8 Service Categories
- ESI: End System Identifier. A globally unique identifier that is similar to a
MAC address.
- SEL: Selector. A one-byte field that can be used by the end system to discriminate
between different services. This field is not used for ATM routing purposes.
ILMI Address Registration
AESA addresses are not completely predefined. Part of each address is defined by the
network manager, and part of it comes from the switch. The complete address is built
using ILMI address registration.
NOTE: This address registration process is not used for E.164 addresses.
When the end system connects to the switch, the 13-byte prefix from the switch is
concatenated to a 7-byte user part defined on the end system. The prefix is composed of
the AFI, DCC/ICD and HO-DSP fields, while the user part contains the ESI and SEL.
The called and calling party numbers (or information elements) that are used during call
setup may be in either native E.164 or AESA address format.
• With E.164 native, the phone-number like address is encoded using IA5 characters,
where (as for ASCII) digit 0 = 30, digit 1 = 31, digit 2 = 32, and so on.
For example, the address 18005551000 would be encoded as:
3138303035353531303030
• As mentioned earlier, E.164 addresses can also be imbedded in an AESA
address. In this case the called/calling party information element indicates that
the address type is AESA and not E.164. The AESA address contains the E.164
address in its prefix.
The following shows how the previous example would be encoded in an imbedded
E.164 AESA address:
Field AFI E.164 HO-DSP ESI SEL
Value 45 000018005551000F 00000000 000000000000 00
Table 1-1: Example of an imbedded E.164 AESA address
Service Categories are a means of characterizing the way ATM traffic should flow through
the network in order to meet bandwidth requirements specific to the type of ATM
application used. Each service category is based on a combination of cell rate pacing,
Quality of Service (QoS) and traffic priority characteristics.
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