[c-nsp] ATM CRC errors
alex at nac.net
Thu Oct 28 09:13:34 EDT 2004
Yes. In show atm vc [vcd], you get (or sho atm vc [int] detail):
cust1.sne>sho atm vc interface a2/0.500 detail
ATM2/0.500: VCD: 1, VPI: 0, VCI: 500
InCellDrops: 0, OutCellDrops: 7
InByteDrops: 0, OutByteDrops: 288
CrcErrors: 29, SarTimeOuts: 0, OverSizedSDUs: 0, LengthViolation: 0, CPIErrors: 0
Out CLP=1 Pkts: 0, Cells: 0O
On Wed, 27 Oct 2004, F. David Sinn wrote:
> The CRC's can be related to lost cell's, since if a component cell (or
> cells) of a AAL5 encapsulated frame are lost, the resultant frame will
> no longer pass CRC checks when the re-assembly is attempted.
> Qwest is correct in saying that discarded cells are most likely the
> cause, and unless they can tell you which VC they are discarding you
> on, you may be out of luck to find out which path is the troublemaker.
> If memory serves, a "sho atm vc" might tell you which VC is having the
> encapsulation error, but it's been years since I had to work on ATM on
> a day-to-day basis, so that may not be the case.
> If you have contracted services that Qwest is policing, you may want to
> double check the shaping on your ends to insure the two match up so as
> to remove the CRC's.
> If there is no policing and this is just a best effort service, then
> CRC's are a fact of life.
> On Oct 27, 2004, at 10:48 AM, James Hamilton wrote:
> > Hi there, we've got an ATM DS3 to Qwest (our telco) for Qwest based
> > T1s and
> > DSL. It's taken ~588 input CRC errors in the last 20 minutes. The
> > count for
> > the last week was ~140,000 CRC's. I've been unable to match these CRC
> > errors
> > to the counters for my interfaces. There were about 100,000 CRC's
> > that I
> > couldn't match to any interface except the main atm1/0 interface.
> > We've checked the physical line, Qwest has monitored the port. They
> > are
> > telling me that discarded cells are the cause. If that is the case
> > shouldn't
> > I be able to match the main interface CRC counter to the CRC counters
> > for all
> > my subinterfaces? Any insight would be appreciated.
> > Thanks
> > --
> > James Hamilton
> > Southwest Cyberport
> > http://www.swcp.com
> > 505-232-7992
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-- Alex Rubenstein, AR97, K2AHR, alex at nac.net, latency, Al Reuben --
-- Net Access Corporation, 800-NET-ME-36, http://www.nac.net --
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