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TOPIC: Discussion About ATM

Discussion About ATM 14 years 4 months ago #6795

  • apit
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i've a questions about ATM
basicly ATM have services called LAN Emulation(LANE)
In my understanding, this service is to enable all application and protocols to work with ATM it true?

Then LANE consists of two components which is LEC and LANE services. LEC allow ATM to communicate with traditional LAN.

what is LANE services function in ATM?
can u give example of LANE services implimented in switches?

i've already configured layer 2 switches..centillion 100 from nortel networks but not really understand about all the LANE stuff although the switches working fine now..need your explanation to understand all of this concept..i'll already read some ATM reference but still not understand it very well....maybe some explanation and on site expirience/hands on from u all can help me..tq :wink:

Re: Discussion About ATM 13 years 10 months ago #9529

  • jwj
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I have a limited experience with ATM LANE. The network I work on had Marconi switches using LANE, but it was switched over to Cisco's using gigabit ethernet, and I must say that was a godsend.

In my understanding, this service is to enable all application and protocols to work with ATM it true?

The purpose of LANE is to mimic the behavior of a normal ethernet LAN over ATM.

Then LANE consists of two components which is LEC and LANE services.

LANE actually consists of four components which I will try my best to explain.
1.) LEC - LAN Emulation Client
The LEC is found where your ethernet LAN is bridging to the ATM LANE. There is one LEC per ELAN. This is where things begin.

2.) LES - LAN Emulation Server
The LES maps mac addresses to atm addresses from the LECs it servers. Keep in mind that LANE uses NSAP addresses (think of them as private IP addresses for ATM). The LES will be on an ATM switch.

3.) BUS - Broadcast and Unknown Server
The BUS will forward the broadcasts, multicasts, and flood unknown addresses from the LES. The BUS will also be found on an ATM switch.

4.) LECS - LAN Emulation Configuration Server
The LECS is the most important part of the LANE configuration. It is basically a database of the ELAN's, and what LES serves them. With Marconi ASX switches, you created the lecs configuration into a file called lecs.cfg, and upload it onto the switch. This is also on the ATM switch.

ELANs do not have to correspond with all the VLANs you have. You can have several different VLANs go over a single ELAN. How many you actually need is something I am not clear on. When our ATM LANE was originally set-up, there was a ELAN for each VLAN. Later down the road, our ATM core took a dump (NSX-9500's suck), and we actually had a Marconi technician sent in to fix it. At that point, they said we didn't need all those ELAN's, and reduced it down significantly. I honestly don't know what affect that had, but our ATM network was doomed because of all the downtime.

At first it was Marconi's equipment acting up (the NSX were scrapped) but the ASX switches are solid as rocks. Our problem was a hardware issue on our ATM to Ethernet bridging card, made by Enterasys. The LECs on one of the switches would go down for no reason at all, forcing us to reboot the switch any time it happened. Towards the bitter end, we were rebooting that switch weekly. There was apparently no fix to it because Enterasys didn't officially support ATM LANE in it's firmware anymore.

So, as can be seen, the switch over to gigabit ethernet has been a blessing. Downtime is limited now to some really old Enterasys and Cisco switches. Any other questions I will do my best to answer.
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