[nsp] 12000 OC12 ATM Card

warner at cats.UCSC.EDU warner at cats.UCSC.EDU
Sun Mar 9 16:20:12 EST 2003

>Daniel Puka said:
>    (Customer 1,2,3)-> (STM1-ATM SWITCH) <-> (OC12 CARD - CISCO 12000)
>     The cisco documentation says that when one vc get congested it can
>use resources from other vc in the same card because it has only one
>single queue for all vcs.
>     One week ago I started to experience very high packet delay during
>the peak usage hours(about 150ms where it was usually 1ms). I am not
>experiencing any packet, cell or crc errors. Is there any change that
>one vc congested from other customer can be the cause of delayed
>packets? My maximum usage is about 90Mbps.

Well, there's always a chance...  But it seems unlikely.  You
should find the delay when you ping your service provider's OC-12
interface that faces you.  If this is gives 150 mS response times
when you're seeing general high packet delay, you should look 
further at the ATM edge stuff.  My guess is that you'll find that the
problem is not in your ATM distribution.  UC Santa Cruz has a very similar
edge setup -- except that in your case the ATM is _not_ oversubscribed.
Every time we have seen this kind of net slowdown (without packet loss)
it has been elsewhere in the service provider's network.

-jim warner, UC Santa Cruz

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