[rbak-nsp] redback-nsp Digest, Vol 36, Issue 7

[David Freedman]

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Thanks to both of you,

>Beware of limitations with l2tp lns and subscriber pwfq combined
>- the l2tp packet needs to come into the box on the same card as you
>handle
>the subscriber circuit. So you can't use the lns-card l2tp session PPA
>circuit loadbalancing feature, nor can you use cross-card LAG on your
>trunk
>carrying the l2tp out toward the LAC.
>- there is no hierarchical qos support

Thankfully haven't had lns card grouping enabled for some time, also not
doing any crosscard LAG. Amazed to see this is still a restriction and
nobody solved this!


>     I'm sure you take this into account already on your network, but it
> bears mentioning for others:  for me an important question to ask when
> deciding whether to rate-limit (setting a fixed rate in "metering"
> downstream or "policing" upstream) or pwfq is the amount of queuing
> resources that the set of subscribers will use; if there are 10k
> subscribers on a card with 8 queues per subscriber, then a card that
> supports 64k queues won't handle it.  It would be necessary to rethink
> the QoS architecture so that the design could be accomplished with 4
> queues & some metering rate-limiters instead.

Since I'm only interested in shaping, I may reduce this to a single
queue in order to save card resources, since as you can see from my
example, they all have the same weight :)

Dave.


- --

David Freedman
Group Network Engineering

david.freedman at uk.clara.net
Tel +44 (0) 20 7685 8000

Claranet Group
21 Southampton Row
London - WC1B 5HA - UK
http://www.claranet.com

Company Registration: 3152737 - Place of registration: England

All the information contained within this electronic message from
Claranet Ltd is covered by the disclaimer at
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