[rbak-nsp] SE800 QoS architecture

[Jim Tyrrell]

Hi,

Thanks for the recent responses regarding QoS profiles - helped my 
understanding and confirmed the way I believed it to work. :)

I'm trying to figure out the best way to interconnect with our provider 
as I understand when utilising QoS in an L2TP setup the subscribers have 
to terminate on the card on which their traffic flows in and out.  
Without QoS we have not worried about through which port a users traffic 
flows or their PPP terminates.  I can a couple of solutions:

1. We have a seperate context, port & tunnel end point for each provider 
link into which the L2TP and PPP terminates.  The only issue with this 
is if one link goes down all sessions on that link go down and have to 
reconnect on the other link, and then will need kicking off once the 
link is restored.

2. As above but we have intercontext routing so if a link fails we stop 
announcing the end point via that link and wont be receiving any routes 
so that it will fall back to a default route to the other context.  Only 
issue I can see is if both links are down both contexts will be 
defaulting to each other and causing a routing loop - will this cause a 
problem?

3. We have a single context with using both ports but 2 seperate 
endpoints and each endpoint is prioritised over a particular link.  We 
would then need to run some sort of PBR to ensure the traffic from each 
endpoint exits via the correct line card.  Then if a link goes down the 
traffic can route over the other link, although QoS wont be functioning 
due to the traffic flowing through the wrong line card (if the PBR can 
detect the failed link and fallback to the other port?)

I'll be gratefull for any feedback as to the best way of terminateing 
and routing L2TP subs on particular line cards, but having routing fall 
back to others in the event of failure.

Thanks.

Jim.