[nsp] 12000 OC12 ATM Card

Daniel Puka daniel.puka at gvt.com.br
Sun Mar 9 22:50:34 EST 2003

 Thanks for the answers.

 The upstream provider is using the 1-Port OC-12 ATM/Engine 0 and the atm
access switch is lucent.

  They are also doing rate limiting for all my incomming IP traffic in
119000 kbps.

  Actually the upstream provider is using the ATM switch to concentrate 3
dedictated STM1/ATM links and some sort of E1/E3 links.

  I have adsl access at my home from an access isp that is buying the other
2 stm1/atm links and for my surprise when I have the high delay they also
experiencing the same in both links.




-----Original Message-----
From: Jared Mauch
To: warner at cats.UCSC.EDU
Cc: cisco-nsp at puck.nether.net; daniel.puka at gvt.com.br
Sent: 09/03/03 21:26
Subject: Re: [nsp] 12000 OC12 ATM Card

On Sun, Mar 09, 2003 at 04:20:12PM -0800, warner at cats.UCSC.EDU wrote:
> >Daniel Puka said:
> >
> >    (Customer 1,2,3)-> (STM1-ATM SWITCH) <-> (OC12 CARD - CISCO
> >
> >     The cisco documentation says that when one vc get congested it
> >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
> >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
> edge setup -- except that in your case the ATM is _not_
> Every time we have seen this kind of net slowdown (without packet
> it has been elsewhere in the service provider's network.

	Assuming you are talking about the Engine0 OC12 ATM card,
they have quite poor performance if you enable any features.  These
include things such as:

	1) Unicast RPF (either strict or the loose check)
	2) Interface ACL
	3) CAR of any sort, including CAR against acl.  (I believe
that Cisco calls it PIRC)

	I'm sure there are other features that may impact
things, including the "DOS Tracker".

	- Jared

Jared Mauch  | pgp key available via finger from jared at puck.nether.net
clue++;      | http://puck.nether.net/~jared/  My statements are only

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