IBM SC30-3681-08 Overview of Related Ilmi Functions, Manual Conguration of the Signaling Version

Overview of LAN Emulation

explicit assignment; by default, 200 of the 256 possible selectors per ESI are reserved for explicit assignment. Run-time selector assignment is bene®cial when you do not need to control the assigned selector, for example, when you are con®guring clients in Classical IP that are not paired with an ARP server.

While ATM addresses must be unique among LE components, LE components can use the same ATM addresses as non-LE components, such as Classical IP servers.

Overview of Related ILMI Functions

ILMI de®nes a set of SNMP-based procedures used to manage the user-network interface (UNI) between an ATM end system and an ATM switch. The following three ILMI functions are particularly relevant to LAN emulation:

1.ATM address registration, which is described in ªAddressing in ATMº on page 257

2.Dynamic determination of the signaling version being run at the switch

3.Acquisition of the LECS ATM addresses

As mentioned in ªAddressing in ATMº on page 257, ATM address registration is a joint effort between ATM end systems and switches. ATM addresses must be registered with the switch before calls can be placed or received.

By default, the ATM interfaces of a router use ILMI procedures to query the switch MIB in an attempt to determine the signaling version (UNI 3.0 or 3.1) being run at the switch. If the query succeeds, the ATM interface runs the same UNI version as the switch; if the query fails, the ATM interface runs UNI 3.0. Alternatively, you can override the default and explicitly con®gure the UNI version that will run on the ATM interface.

Manual Con®guration of the Signaling Version

You need to con®gure the signaling version manually if the ATM switch runs UNI 3.1 and has no UNI Version MIB variable. In this case, the ATM interface cannot dynamically determine the UNI version. Because the ATM interface in the router uses UNI 3.0 by default, you should manually con®gure the ATM interface to use UNI 3.1.

Locating the LECS Using ILMI

ILMI is the method of choice for locating the LECS. The ILMI MIB at the ATM switch includes a list of LECS ATM addresses that can be retrieved by LE clients. This method is useful because the LECS ATM addresses need only be con®gured at ATM switches, not at LE clients, and there are fewer switches than LE clients. Clients attempt to connect to the ®rst LECS on this list. If the connection fails, they try the next LECS address in succession until a connection is established.

Chapter 20. Overview of LAN Emulation 259