ATM Administration
52
An ELAN has two primary functions which are directly relevant to this
presentation of ATM Addresses:
❑
It provides a broadcast data path in a connection-based ATM network.
❑
It provides address registration and resolution to the LES and LEC.
It also matches MAC addresses to ATM addresses.
LANE has been subdivided into the four major components shown below
and, as each is discussed in Appendix B, they will not be duplicated here.
1.
LAN Emulation Client (LEC)
2.
LAN Emulation Services
— LAN Emulation Server (LES)
— Broadcast and Unknown Server (BUS)
— LAN Emulation Configuration Server (LECS)
Briefly. Omega management enables you to access and configure your switch
to ELANs — with or without a network accessible LECS.
ELAN Membership
As presented in Chapter 1, prior to Release 2.4 an “ATMcentric” network
mandated that before switching any packets on the Ethernet ports, the
switch HAD to use an LECS for MAC Address determination to connect to,
and maintain, an ELAN. This meant that if the connection to the ELAN was
dropped for any reason, then any device communicating on that ELAN would
cease to operate.
Prior to Release 2.4, a standalone switch would not know which ELAN to join
without an LECS. It necessarily followed that, if the LECS was not available,
it was neither possible to configure devices nor forward packets.
Further, the “downing” of an ELAN (the LES is inoperative) and the
subsequent change in the network topology, would force the switch to
reconfigure.
Release 2.4 allows a standalone switch an alternative to LECS address
determination. Your switch now has the ability to perform local Ethernet
forwarding for devices when:
the LECS is not available,
the LES for an ELAN is not available,
the ATM Physical Media Module is not installed,
the ATM fiber connection is not present.
