Since we have been quoting Cisco statistics lately, here's one that is
actually quite helpful. Cisco says you should not have more than one CRC
error per megabyte of data on a serial link. The reason they use megabytes
instead of packets is because it's hard to know how big your packets are.
(The thinking is that one error per packet when using 64-byte packets would
be a much higher rate than one error per packet when using 4500-byte
packets, for example.)
The reason they use bytes instead of bits is simply because this statistic
really comes from the protocol analyzer vendors, not Cisco, and those
vendors report statistics in bytes. If you're looking at Cisco output and
it shows bits, be sure to divide by 8 to get bytes.
You should compare the CRCs to the input data, rather than the output data,
I would think, since there's no way to really know if your outputted
packets are encountering problems in transit.
Hope this helps.
Priscilla
At 01:40 PM 8/31/00, Rossetti, Stan wrote:
>Does anybody know what is considered to be high CRC errors on a serial line.
>I have seen 26 crc errors over last 70 hours (8,980,742 input packets) appr.
>= 2.895 x 10 -6 error rate (26/8,980,742).
>
>Is the error rate formula (crc error total)/(input error packets). Or is it
>(crc error total)/(output error packets) or (crc error total)/(input +
>output error packets). Do you use the number of packets or is it bits or is
>bytes. I would assume that you use packets.
>
>Thanks,
>
>Stan Rossetti
>
>
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