[nsp] Assymetrical DS3 errors?

From: Deepak Jain (deepak@ai.net)
Date: Sat Jan 06 2001 - 13:44:40 EST


Here is a strange problem, or at least one I haven't seen before. :)

I have a point-to-point DS3 that is brand new, on new PA-2T3+ boards.

reno <--> denver

Traffic pushed from reno to denver works great, and there is no
detectable packet loss.

However, (and the symptom that caused this investigation) is FTP
transactions going from the equipment connected to denver back to
equipment connected to reno stops or stalls at around 20KB/s. The reverse
(as to all downloads/web transactions/etc) are fine. Browsing the servers
with FTP is also fine. The strange thing is that the direction of the DS3
that should be congested (reno -> denver) is the fast/working FTP path,
the other is unusable.

Looking for hardware causes, on denver, the DS3 facing Reno picks up a
small number of errors every 10-20 minutes.

denver>sh in s6/1
Serial6/1 is up, line protocol is up
  Hardware is M2T-T3+ pa
  Internet address is 205.134.160.26/30
  MTU 4470 bytes, BW 44210 Kbit, DLY 200 usec,
     reliability 255/255, txload 1/255, rxload 249/255
  Encapsulation HDLC, crc 16, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:00, output 00:00:01, output hang never
  Last clearing of "show interface" counters 20:49:50
  Queueing strategy: fifo
  Output queue 0/40, 0 drops; input queue 0/75, 0 drops
  30 second input rate 43189000 bits/sec, 10064 packets/sec
  30 second output rate 1000 bits/sec, 1 packets/sec
     567522756 packets input, 620657675 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
              0 parity
     733 input errors, 12 CRC, 0 frame, 0 overrun, 0 ignored, 721 abort
     254394920 packets output, 2731517129 bytes, 0 underruns
     0 output errors, 0 applique, 0 interface resets
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions
   rxLOS inactive, rxLOF inactive, rxAIS inactive
   txAIS inactive, rxRAI inactive, txRAI inactive

On reno, there are no errors shown:

reno#sh in s1/0/1
Serial1/0/1 is up, line protocol is up
  Hardware is cyBus PODS3+ Serial
  Internet address is 205.134.160.25/30
  MTU 4470 bytes, BW 44210 Kbit, DLY 200 usec, rely 255/255, load 247/255
  Encapsulation HDLC, loopback not set, keepalive set (10 sec)
  Last input 00:00:01, output 00:00:00, output hang never
  Last clearing of "show interface" counters 00:11:17
  Queueing strategy: fifo
  Output queue 0/512, 416138 drops; input queue 0/512, 0 drops
  5 minute input rate 18000 bits/sec, 0 packets/sec
  5 minute output rate 42961000 bits/sec, 9839 packets/sec
     7584 packets input, 7166182 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants
              0 parity
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     6732180 packets output, 3704026139 bytes, 35 underruns
     0 output errors, 0 applique, 0 interface resets
     0 output buffers copied, 0 interrupts, 0 failures
     0 carrier transitions
   rxLOS inactive, rxLOF inactive, rxAIS inactive
   txAIS inactive, rxRAI inactive, txRAI inactive

--

Symmetrical traceroutes confirm the traffic is actually going over the DS3 in question and not over some crazy internet path.

Any help would be very appreciated, I'd like to figure out what's going on as opposed to replacing everything until the problem goes away. :)

Thanks,

Deepak



This archive was generated by hypermail 2b29 : Sun Aug 04 2002 - 04:12:24 EDT