Ok, I'll take a stab at it.
First a question. Have there been any BERT tests end to end (NID to frame
switch interface)? If so, was an all zero's test done?
Very simply, I suspect that one of the circuit's repeaters is misconfigured
ESF, AMI. Everything works fine until the 1's density isn't high enough to
keep zero suppression from kicking in. Then one of the bits is being set to
1, causing the CRC.
Why would telnet show a problem? Easy, IP packets are 64 bytes minimum.
Telnet sends a packet for each character, the rest of the data block has to
be padded with something. Some telnet clients padd with zeros, hence the
CRC errors when zero suppression kicks in when these packets traverse the
link. Other telnet clients pad with all 1's or ctrl-Z or ctrl-D, and won't
cause the zero suppression, therefore no CRC's.
There's only two ways out of this, the carrier tracks down the misconfigured
repeater, or you have them reconfigure for 56K channels.
Let me know if I'm right and about that job. :))
Rodgers Moore, CCDP, CCNP-Security
""Fred Flinstone"" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> ok here it goes....
>
> we have a customer we manage that is incurring CRC'c, input errors etc on
> there serial interface.
>
> 1. stress tested the circuit many times from the frame cloud through the
csu
> as good
> 2. tries verious cables
> 3. there are no interface modules i believe its a 2500 something router
but
> i can check
> 4. the only times crc's cross the link (verified by a protocol analyzer)
is
> when we telnet from our management platform to the site...even if i just
> enter one character in the telnet session crc's increment
> 5. if you telnet from a neighboring router or dial in this produces no
crc's
> what so ever.
> -
> we have 3rd level engineers looking at this i bet if you find an answer I
> could get you a nice paying job...:) (well maybe)
> -
> any help would be appreiciated
> -
> thanks...kyle
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