Output drops even low input rate

[Rojer-bkk]

Hi Expert,

I found increasing of total output drops and output queue drops even input rate was low and no qos apply on this interface. I plan to increase hold queue out for output queue. I'm unsure it would help. Appreciated all feedback. Thank you.

Router 1941, 15.0(1)M4

Serial0/0/0 is up, line protocol is up

  Hardware is WIC MBRD Serial

Internet address is 10.182.6.30/30

  MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,

     reliability 255/255, txload 2/255, rxload 1/255

  Encapsulation HDLC, loopback not set

  Keepalive set (10 sec)

  Last input 00:00:00, output 00:00:00, output hang never

  Last clearing of "show interface" counters 05:28:09

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 815

  Queueing strategy: weighted fair

  Output queue: 0/1000/64/815 (size/max total/threshold/drops)

     Conversations  0/242/256 (active/max active/max total)

     Reserved Conversations 0/0 (allocated/max allocated)

     Available Bandwidth 1158 kilobits/sec

  30 second input rate 8000 bits/sec, 11 packets/sec

  30 second output rate 17000 bits/sec, 10 packets/sec

     204215 packets input, 36837512 bytes, 0 no buffer

     Received 1969 broadcasts, 0 runts, 0 giants, 0 throttles

     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

     163256 packets output, 90521035 bytes, 0 underruns

     0 output errors, 0 collisions, 0 interface resets

     0 unknown protocol drops

     0 output buffer failures, 0 output buffers swapped out

     0 carrier transitions

     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

[Joseph W. Doherty · Accepted solution]

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Posting

Although your 30 second transmission rate is low at the time you captured these stats, the fact you had both 242 concurrent flows queued and that you had 815 drops implied sometime during the last 5:28 hours you had congestion.

For a T1, the default WFQ that's running on the interface is difficult to improve on without additional analysis.

Unless you do perform additional analysis, just increasing queue depth might be counter productive.