4-6. ATM LANE

LANE provides an emulated IEEE 802.3 Ethernet or IEEE 802.5 Token Ring network over an ATM network. You can use LANE to transport traditional LANs over an ATM backbone or an ATM WAN cloud.
LANE uses the concept of emulated LANs, or ELANs, to segment traffic into logical networks within the ATM domain.
LANE consists of several logical components, each configured on a router, switch, or an ATM switch:
- LAN Emulation Configuration Server (LECS) The central administrative control point for all ELANs in a domain. The LECS keeps a database of ELANs and the ATM addresses of the LANE servers that control each ELAN. (Each administrative domain has only one LECS.)
- LAN Emulation Server (LES) The central control point for all LANE Clients in an ELAN. The LES provides MAC to ATM Network Service Access Point (NSAP) address translation for each LANE Client. (Each ELAN has only one LES.)
- Broadcast and Unknown Server (BUS) The BUS handles all broadcasts sent from a LANE host. The LANE Client must forward any broadcast or multicast from an end user to the BUS. The BUS is then able to replicate the broadcast to all other LANE Clients in the domain.
- LAN Emulation Client (LEC) provides the basic ELAN function at the edge of the ATM network. The LEC emulates an interface to a tradition LAN and provides data forwarding, address resolution, and MAC address registration with the other LANE components. A LEC is needed at any location where network layer addresses are used.
You can configure multiple LANE components in the network for redundancy. Simple Server Redundancy Protocol (SSRP) handles the communication between the active and standby components so that no single point of failure can exist within the components.
NOTE
ATM addresses use the NSAP format, a 20-byte value. Typically, NSAP addresses are written out as groups of four hex digits separated by dots. The leftmost and rightmost two hex digits are usually grouped by themselves. The address is composed of the following parts:
Prefix a 13-byte field that uniquely identifies every ATM switch in the network. Cisco ATM switches uses a predefined 7-byte value of 47.0091.8100.0000 followed by the 6-byte MAC address of the switch.
End-System Identifier (ESI) a 6-byte field that uniquely identifies every device attached to an ATM switch. Typically, this is the 6-byte MAC address of the device (an ATM router interface or LANE module, for example).
Selector A 1-byte field that identifies a process running on an ATM device. Cisco devices usually use the ATM sub interface number as the selector value. Be sure to convert the ATM sub interface number from decimal to hex before configuring the selector byte on a Cisco switch.
The prefix value always comes from the ATM switch. The ESI value is determined from the ATM interface MAC address as follows: LEC (MAC address), LES (MAC address + 1), BUS (MAC address + 2), and LECS (MAC address + 3). The selector is the ATM sub interface number except for the LECS, which must always be configured on a major ATM interface (selector 00).