l2tpns - high volume L2TP tunnel termination

I went into this talk rather blind; having failed to do any homework. I?d only heard of L2TP in the context of VPNs, and wasn?t really sure what it was or did, so much of Brendan?s talk went over my head. His company?s been using L2TP as the transport for the PPP links of their DSL customers, and he talked about the issues related to doing this stuff in really high volume.

Particularly interesting were the clusters they have set up to handle the connections. They have a bunch of machines communicating via IP multicast; adding new machines to the cluster just involves plugging them in and turning them on. IP multicast is definitely something that I?m going to have to properly read up on, as all the new cool things seem to be using (c.f. Avahi in particular).

Also really interesting was a question one of the audience members asked. The L2TP implementation they?re using is an open source project (you can find the Source Forge project here) and the question was: what did you get by doing it this way and not just buying a Cisco XYZ?

Freedom and flexibility are the big wins. It hasn?t been any cheaper to go the open?source route compared to buying a black box from Cisco, but that?s only true for the first box. He mentioned that they?ve recently installed new DSLAMs, but they just can?t do some of the things they want to; the functionality?s been added to l2tpns, something they couldn?t do if they were running a proprietry solution.

Apparently, if they had to do it again they?d do it this way. It?s nice to hear an open?source success story from the trenches, even when I don?t really understand the finer details.