Information Technology Reference
In-Depth Information
ATM LANE Components (Continued)
Table 4-12
ATM LANE Component
Description
Broadcast and Unknown Server (BUS)
The BUS handles all broadcast, multicast packets, and unicasts
sent to unknown destinations. Because broadcasts do not exist
in ATM, the BUS processes the broadcasts to create virtual
circuits to all stations in the ELAN. The LES and BUS
functions are commonly implemented in the same device.
LANE Join and Circuit Establishment Operation
When a new station joins the ELAN, the following procedure occurs:
The LEC requests the ATM address of the LES from the LECS. The LECS provides the
address.
1
The LEC contacts the LES to join the ELAN.
2
The LES adds the LEC to the ELAN and sends a response to the LEC.
3
The LEC sends an LE-ARP to the LES to obtain the ATM address of the BUS. The LES
provides the address.
4
The LEC contacts the BUS, which adds the LEC to the Multicast Send Virtual Circuit
Connection.
5
After the LEC is ready to communicate with a destination station but does not have the desti-
nation ATM address, it sends an LE-ARP request to the LES. If the LES knows the destination
ATM address, it provides it to the LEC. If the LES does not know the ATM destination address,
it sends an LE-ARP to all LECs, the destination LEC responds to the LES, and the ATM address
is forwarded to the sending LEC. Then, the sending LEC sets up a virtual circuit to the destina-
tion LEC.
SSRP
SSRP is a Cisco proprietary protocol that provides replication for LECS or LES/BUS services.
With SSRP, if the active LES and BUS device fails, another device assumes the roles of LES
and BUS. Also, if the active LECS fails, another device assumes the role of the LECS. The
active and secondary services do not run concurrently on the ELAN.
A sample configuration of SSRP can be found at the following site:
www.cisco.com/warp/public/121/ssrpconfig.html
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