[nsp] l2tp-cpu load

[Andrew Fort]

Andy Furnell wrote:

>Remember the number of tunnels will affect performance much more than the 
>number of sessions... if you can aggregate the l2tp tunnels so only one tunnel
>is presented to your LNS you'll get much better performance than if you're 
>forming hundreds of l2tp tunnels to hundreds of LACs with a similar number
>of active sessions.
>
>If the cash is there you'll have get much better performance from an NPE-G1.
>>From speaking to people using them as a broadband LNS they seem to be able
>to take an STM-1's worth of traffic in about 5500 sessions without breaking
>a sweat :)
>  
>

Aggregating sessions into fewer tunnels is great advice, demand it of 
your tail provider :).  Tunnel setup/breakdown is also particularly 
costly; I've seen a single user flapping their PPP session wildly (auth 
failures) due to dodgy clientside firmware as many as 40 times a second 
cause grief to an npe-400.