The ultimate goal of the LES is to arrange and control connections with a LEC. This connection is commonly
known as a control direct ATM virtual channel connection (VCC). After this connection is established, it will
handle address resolution and registration responses.
Note The LES establishes communication with the LECS and provides verification information for
LECs attempting to join. The LES does not maintain a constant connection with the BUS.
The LES only provides each LEC with the ATM address of the BUS for forwarding.
The LANE servers provide the address registration and resolution functions. These functions include
collecting address and route descriptor types based on the LANE standard. Let’s take a look at the address
resolution process, which is shown in Figure 8.6 and outlined as follows:
Figure 8.6: The LES address resolution process.
A workstation connects to a router or ATM switch and performs a physical outbound packet
transmission. This example uses the Address Resolution Protocol (ARP) query to try to locate a
device on a remote segment.
Note The local router is typically the ATM LEC and provides the circuit for the initial ATM address
mapping.
1.
The LEC takes an Ethernet frame and assigns an immediate LEC link, which is used to obtain the
ATM address identifier needed to establish an ATM connection. If this process is not successful, the
LEC must locate a LES.
2.
The LES circuit holds the main ATM network address table and returns with the VCI assignment.3.
LAN Emulation Configuration Server (LECS)
The LECS provides key services such as registration for Integrated Local Management Interface (ILMI) and
configuration support for the LES addresses for the corresponding emulated LAN identifiers.
The LECS contains a database of ATM addresses for the LES and BUS pairs for known ELANs. The LEC
consults the LECS to determine the LES’s ATM address when it first joins an ELAN.
Note At least one LECS is required per ATM LANE switch cloud.
The LECS has the following functions:
Registers the LECS ATM addresses for known ELANs• Supplies LECs with LESs’ ATM addresses• Provides interfaces to the LEC and the LES•
The registration process of the LECS ATM address uses the ILMI functions to connect to the ATM network;
this situation usually includes an ATM switch. Support for configurations from the LECS ensures that the
correct LES address is supplied to the LEC.
170