Muni fiber: L1 or L2?

Wed Feb 6 22:04:04 UTC 2013

On 13-02-06 16:53, Scott Helms wrote:

> You realize that most commonly the L2TP LAC and LNS are just routers right?
>  You're not getting rid of boxes, you're just getting rid of the only open
> access technology that's had significant success in the US or Europe.

Actually, there is a cost. In lower end Juniper routers, when you
combine both L2TP and PPPoE, the total performance of the LNS router
drops significantly because the interface cards can't do both at same
time so the traffic must travel the backpane to the CPU/auxiliary
processor for the second step.

(at the LAC level, there is less overhead because PPPoE packets are just
passed to the L2TP side, but at LNS, PPPoE packets have to be processed).

Apparently, Juniper has worked to reduce this performance penalty in
newer routers. But routers such as the ERX310 suffered from this quite a
bit. (throughput of about 1.5mbps from what I have been told).