ATM LANE
Cisco removed ATM LANE as a CCIE Routing and Switching lab exam topic but has retained it in the CCIE written blueprint, but with less emphasis. Know the LANE components and the SSRP that are used for redundancy. This section only covers LANE. Other ATM topics are covered in Chapter 5, "Wide-Area Networks."
LANE provides connectivity between Ethernet or Token Ring stations and ATM connected stations. LANE also provides connectivity for Ethernet or Token Ring stations across an ATM network. LANE creates an emulated LAN (ELAN) for each LAN segment it connects to.
ATM LANE Components
The components of ATM LANE are shown in Table 4-12.
Table 4-12 ATM LANE Components
|
ATM LANE Component |
Description |
|
LANE Client (LEC) |
There is a LEC for each member of the ELAN. LECs implement LE-ARP address resolution and emulate a LAN for higher-level protocols. LEC builds a table to map MAC addresses to ATM addresses. Each LEC has an ATM address. LECs can be a computer station, switch, or router. |
|
LANE Server (LES) |
The LES is the central resource for the ELAN. It provides management of all stations in the ELAN by providing address registration and resolution, and handling LE-ARP requests. |
|
LANE Configuration Server (LECS) |
A LEC consults the LECS when first joining the ELAN. The LECS provides the ATM address of the LES to the LEC. |
|
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.
The LEC contacts the LES to join the ELAN.
The LES adds the LEC to the ELAN and sends a response to the LEC.
The LEC sends an LE-ARP to the LES to obtain the ATM address of the BUS. The LES provides the address.
The LEC contacts the BUS, which adds the LEC to the Multicast Send Virtual Circuit Connection.
After the LEC is ready to communicate with a destination station but does not have the destination 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 destination 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