Fore Systems forerunner series, Configuration Manual

Page: 76 / 352

2 - 4
ForeRunner ATM Switch Network Configuration Manual
Configuring Classical IP
2.2 Address Registration and ILMI
Before a host can establish connections over a physical interface, the host must know the
NSAP address for that interface. The primary purpose of Interim Local Management Interface
(ILMI) is to discover and register these NSAP addresses dynamically.
2.2.1 NSAP Addresses
For private ATM networks, addresses uniquely identify ATM endpoints. The UNI 3.0 address
format is modeled after that of an OSI Network Service Access Point, hence the name NSAP
address.
Three address formats have been specified: DCC, ICD, and E.164. FORE implements the ICD
ATM format. Per the UNI 3.0 specification, all private networks should accept initial call set-
up messages containing ATM addresses with any of the approved formats and forward the
calls as necessary.
An NSAP address consists of the following:
• a 13-byte network-side prefix - The prefix is the NSAP prefix of the switch to
which the host is attached.
• a seven-byte user-side part - This consists of the following:
- a six-byte End System Identifier (ESI) - The ESI is the unique IEEE MAC
address of the interface.
- a one-byte selector - Although each Classical IP interface for a given physical
interface uses the same prefix and ESI, the selector field is the part that indi-
cates the number of the specific Classical IP interface. On a switch, the selec-
tor field is 00 for qaa0, 01 for qaa1, 02 for qaa2, and 03 for qaa3.