[c-nsp] Need help troubleshooting CRC errors

[Ziv Leyes]

I've seen similar situations where a shaping fine tuning in the carrier equipment's settings solved the CRC errors.
All the ATM VP/VC related equipment in the circuit should be shaped properly, depending on what type of service you get, CBR, VBR, etc.
Either too high or too low values could cause cells drops thus rising the CRC errors. A 20% overhead needs to be taken in count for ATM to non-ATM conversions in the circuit
HTH
Ziv


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Gert Doering
Sent: Saturday, September 19, 2009 7:26 PM
To: Steven Pfister
Cc: cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] Need help troubleshooting CRC errors

Hi,

On Thu, Sep 17, 2009 at 10:39:21AM -0400, Steven Pfister wrote:
> that pretty much every one of them is showing what I think is a rather 
> high receive error count on the 3640 end of the OC3 connection, and it 
> all seems to be CRC errors. Not much of any errors are showing up on 
> the 8510 end of the OC3 connection. For example, one site yesterday 
> late afternoon showed 63, 763 receive errors for the day. Several 
> others were in the 20Ks. I'm not really certain what the cause might 
> be, or where to start. Can anyone help?

Is there a carrier network in between?  In our cases, whenever we saw ATM CRC errors, it was due to dropped cells in the carrier network (overloaded).  If the receiving router cannot reassemble a packet due to missing cells -> CRC error.

If the STM-1 is "direct", no carrier ATM gear in between (just SDH/SONET)
gear, it be a bad line.   In that case it won't be cell drops.

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de

 
 
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