[c-nsp] PPPoe Access Concetrators

[Andrew Fort]

Robert E.Seastrom wrote:

> Soapbox:
> 
> The world could certainly do with an LNS/LAC/tunnelswitch platform
> that ran on commodity PC hardware.  Plenty of CPU and RAM bandwidth to
> do a few hundred megs of bit-banging, stripping headers off and
> putting them back on again.
> 
> Unfortunately, just as is the case every time someone starts talking
> about using PCs as core routers for small networks, the devil is in
> the details and feature sets that one needs to get the job done.

Well, I'd argue for some jobs the feature set problem is well taken care of.

The "no. 2" Australian telco uses (and develops) L2TPNS as their LNS for 
their (residental ) ADSL product.

http://sourceforge.net/projects/l2tpns

Admittedly it's only half the picture, but if you have the telco 
supplying you the LAC function (as is the case in Australia and I 
suspect elsewhere), it makes sense to consider this for replacing a 7x00 
as LNS. It supports basically everything you'd need for the LNS part of 
the job, including announcing BGP prefixes (IOS like config and 
everything), rate-limiting and the like.  Its design allows for 
clustering to share load between boxes, too.

With general purpose unix machine-routing, inevitably the devils lie in 
handling traffic; polling vs. interrupts, interrupt coelescing, and the 
likes.  Linux has improved vastly in this area over the last three 
years (thanks to Luca Deri amongst others), to the point where some 
(such as the above telco) rely upon it for a quite significant volume of 
traffic.

-andrew