ATM Administration
58
ATM addresses
As presented in the introduction to this chapter, the function of the ELAN
protocol is to emulate (defined as: to imitate, to equal, or to approach equality
with) a local area network to an ATM network. Specifically, the ELAN
protocol defines the mechanisms that allow the emulation of an IEEE 802.3
Ethernet LAN. In other words, ELAN protocols for Ethernet make an ATM
network look and behave like an Ethernet LAN.
The bottom line is that ELAN allows Ethernet repeaters, workstations and
servers to transparently communicate across, and within, an ATM network.
Address
Registration and
Resolution
Address Registration is the mechanism by which LECs provide address
information to the LES.
Address Resolution, on the other hand, is a procedure in which a LEC
associates a LAN destination with the ATM address of another client or the
Broadcast and Unknown Server (BUS). An intelligent LES may respond to
address resolution requests if LECs register their LAN destinations (defined
as MAC addresses) with the LES. Address resolution allows LECs to set up
data direct Virtual Channel Connections (VCCs) to carry frames.
That is, when a LEC is presented with a frame for transmission whose LAN
destination is unknown to that client, it must issue a LAN emulation address
resolution protocol request frame to the LES over its control point-to-point
VCC. The ATM protocol requires a destination ATM address to set up a
connection across the network. Yet most people will only “know” the MAC
address of the destination.
Address
Determination
As noted in Chapter 1, Product Description, there is user-defined emulated
LAN support for up to 64 ELANs using either port or MAC addresses.
Normally, an ATM address consists of a network prefix, a MAC address and a
selector byte.
[network prefix] [MAC address] [selector byte]
Network Prefix.
The network prefix is determined through the Interim
Local Management Interface (ILMI)
protocol
which
automatically registers all
64 ATM addresses with the LECS.
[network prefix]
[MAC address] [selector byte]
During the power on cycle, internal tests are automatically run to test the
integrity of the CPU and memory. After the tests are successfully completed,
a request is sent to the ATM switch for a network prefix assignment. When
the network prefix is returned, the switch creates 64 ATM addresses.
MAC Address.
Each port has its own MAC address and can be determined
as follows:
A base MAC address has been assigned to each switch by the manufacturer.
[network prefix] [
MAC address
] [selector byte]
