Скачать или смотреть ATM and LAN Integration - 7 : LANE

Full playlist of #ATM covers various aspects like ATM basics, ATM operation, ATM #QoS & integration with #LAN
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Local Area Network Emulation or LANE is the protocol of choice today to help legacy networks and ATM interoperate.


LANE supports operation with both Ethernet and token ring.

The most important point about LANE is that it emulates the Ethernet protocol, not Ethernet operation. This means that LANE only appears to be Ethernet - there is no CSMA/CD process, no collisions, and no Ethernet limitations. LANE was designed simply as a way to allow Ethernet and ATM networks to work together.


LANE is configured directly on computers and switches. LANE groups users into Emulated LANs, or ELANs. These operate like VLANs. Communication within an ELAN is bridged and communication between ELANs is routed.


LANE operates this way:

A workstation has an ATM adapter card installed instead of an Ethernet adapter. When the workstation sends data, the data is first converted into an Ethernet frame, and then broken up and converted again into ATM cells. The reason one Ethernet frame becomes many cells is because, as we discussed, ATM cells are much smaller than Ethernet frames-53 bytes versus over a thousand bytes. The creation of cells from frames is called Segmentation and Reassembly, or, more simply, SAR. And as the name applies, the opposite process occurs at the destination.


Once the frame is converted to ATM cells, a special ATM address is required to cross the ATM network. One of LANE's main features is the ability to build a database that contains mappings of all Ethernet addresses to ATM addresses.


Once the ATM address is located, it is used to set-up the connection and send the cells on their way. Once the destination ATM station is reached, the SAR process reassembles the Ethernet frame for final processing.

Often networks are created with ATM and Ethernet workstations. In this case, the ATM switch closest to the final destination converts the data to Ethernet, then forwards it as a normal Ethernet packet.


So, to recap, LANE converts the packet to an Ethernet frame first, then uses the SAR function to create ATM cells. LANE then converts the Ethernet destination address to an ATM address and forwards the packet across the network. At the other end the reverse happens-cells are converted back to frames and sent on to their final destination.