[28271] in North American Network Operators' Group
Re: Anyone encountered Cisco ATM PVC large delay bug?
daemon@ATHENA.MIT.EDU (Alexei Roudnev)
Sun Apr 23 04:44:00 2000
Message-ID: <011501bfacff$7017a920$524b1c26@genesyslab.com>
From: "Alexei Roudnev" <alex@relcom.EU.net>
To: "Yu Ning" <yuning@cndata.com>, "Alex Rubenstein" <alex@nac.net>
Cc: "nanog-post" <nanog@merit.edu>
Date: Sun, 23 Apr 2000 01:39:24 -0700
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I think, the clue is in your accounting - you have 100% used bandwidth when you propose 80%.
ATM bandwidth is a pretty twisted thing.
If so, some queueries appear and it explain the delays.
----- Original Message -----
From: "Yu Ning" <yuning@cndata.com>
To: "Alex Rubenstein" <alex@nac.net>
Cc: "nanog-post" <nanog@merit.edu>
Sent: Thursday, April 20, 2000 5:06 PM
Subject: Re: Anyone encountered Cisco ATM PVC large delay bug?
> Hi,
>
> ----- Original Message -----
> From: Alex Rubenstein <alex@nac.net>
> To: Yu Ning <yuning@cndata.com>
> Cc: nanog-post <nanog@merit.edu>
> Sent: Friday, April 21, 2000 8:01 AM
> Subject: Re: Anyone encountered Cisco ATM PVC large delay bug?
>
>
> >
> >
> >
> > Are you accounting for ATM overhead? Remember, the sho in bits/sec do NOT
> > count overhead (another words, they are looking at true bits/sec, not
> > cells/sec).
> >
> > You should check cells/sec on the ATM port you are connected to.
> >
> Yes. I get the utilization statistic from ATM PVC statistic.
>
>
> >
> >
> >
> > > In more detail, our situation is: if we get a high bandwidth PVC,
> > > say 51M(or 80M), and if the bandwidth utilization reaches 80%
> > > percent, the ATM link will encounter a 1500~2000 ms delay - just
> > > point to point ping across the link. We have found this situation
> > > is associated with "sar txpool" setting in Cisco GSR, and a manipulation
> > > of the "sar txpool" together with bandwidth increasing has solved
> > > the problem now.
> > >
> > > But I still wonder if any of you ever encounter this situation(bug),
> > > and how did you overcome it? If you are still puzzled by this bug,
> > > I'd like share our temp solution with you.
> > >
> > >
> > > regards,
> > >
> > > Yu Ning
> > >
> > > -------------------------------------------
> > > (Mr.) Yu Ning
> > > ChinaNet Backbone Operation
> > > Networking Dep.,Datacom Bureau
> > > China Telecom.,Beijing(100088),P.R.C
> > > +86-10-66418121/66418122/66418123(fax)
> > > -------------------------------------------
> > >
> >
> >
>
