21CN Virtual Paths?

Hi guys,

Quick and simple question: Does BT's 21CN MSANs use a Virtual Path system like the old ATM DSLAMs?

I thought Virtual Circuits only run on ATM but I just want to check

It doesn't use ATM Virtual Paths, but it does have a vague equivalent, the SVLAN (Service Virtual Local Area Network); if you've ever encountered 802.1q VLANs in Ethernet kit, that's the same basic idea, but in BT's 21CN kit, SVLANs can be given guaranteed service levels (e.g. "this SVLAN always gets 100MBit/s of traffic; this SVLAN can be given up to 500MBit/s of traffic, but always gets 20MBit/s).

Edited by farnz (Fri 09-Sep-11 20:21:47)

Thanks for your reply.

Any idea what the average SVLAN size is?

Do BT Wholesale allow SVLANs to congest as much as ATM Virtual Paths before they add more capacity?

Unfortunately, I have no idea what the answers are to any of your questions.

I know that the physical links are gigabit or faster Ethernet, so I'd expect the SVLANs to be fairly well provisioned. It's also much cheaper for BTW to run the physical links at high speeds - IIRC, BTW estimated that the 10G Ethernet links cost about the same as 155M ATM links, so I would expect them to be better about not letting SVLANs run hot.

Against that, the monitoring for SVLANs didn't work correctly when they were first deployed - this is now fixed, but there was a period when BTW simply couldn't see that they were running an SVLAN hot, and relied on complaints to get it fixed.