Cisco 2600 Router and output errors

I have a cisoc 2600 router with the following configuration:

Serial0/0 is up, line protocol is up
  Hardware is PQUICC with Fractional T1 CSU/DSU
  Description: XXXXX
  Internet address is 192.XX.XX.XX/30
  MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
     reliability 255/255, txload 251/255, rxload 7/255
  Encapsulation HDLC, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:03, output 00:00:00, output hang never
  Last clearing of "show interface" counters 00:36:39
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 3423
  Queueing strategy: weighted fair
  Output queue: 52/1000/64/3423 (size/max total/threshold/drops)
     Conversations  6/21/256 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
  5 minute input rate 44000 bits/sec, 105 packets/sec
  5 minute output rate 1525000 bits/sec, 188 packets/sec
     247298 packets input, 13419443 bytes, 0 no buffer
     Received 257 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     435427 packets output, 419286470 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions
     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

We have a full T1 connected to it and keep receiveing these output errors.  the application on the other side is behind about 1 miute.  is there a way to troubleshoot this to see where all the bandwidth is going and why we are constatly increasing in output errors?
exiscapitalAsked:
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stressedout2004Commented:
Which output errors are you referring to? From the output above it is showing 0 output errors.
0
exiscapitalAuthor Commented:
Last clearing of "show interface" counters 00:36:39
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 3423

 now they are at:

  Last clearing of "show interface" counters 01:00:39
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 5396
0
exiscapitalAuthor Commented:
Sorry meant output drops
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pjtemplinCommented:
Those are dropped packets, not "errors".

Need more bandwidth.  In the mean time, you might be able to prioritize some traffic through various QoS configurations to give your preferred application some temporary help.
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exiscapitalAuthor Commented:
only running two applications both are high priority.  
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pjtemplinCommented:
Then you'll need more bandwidth.  You're running that T1 at 98-99% outbound usage (251/255 txload).  You're averaging packet sizes of 1000B, so you're doing well.
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pjtemplinCommented:
Also, in your original output, your output queue shows 52 packets queued up for delivery.  Since a 1500-byte packet takes 8ms to send, a 1000-byte packet takes about 5ms.  With 52 packets queued up, you're already at 250ms queueing delay.
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stressedout2004Commented:
You can try increasing the output hold queue size in increments with the command "hold-queue out" in interface configuration or turn off fast switching on the interface.
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pjtemplinCommented:
Turning off fast switching won't help.  Increasing the hold-queue won't do much - there isn't enough pipe to carry the packets.  Queueing more up only means more delay to empty the buffer, and potentially more TCP retransmissions to fill in packets that are supposedly lost.
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exiscapitalAuthor Commented:
is there a way I could determine whichj application is consuming most of the bandwidth?  
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pjtemplinCommented:
You could use an ACL to figure out which one is consuming the most PPS, but you'd probably need an external tool (perhaps netflow) to determine bandwidth.
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ChopperCenturyCommented:
That sure is alot of drops for just 36 minutes of counter logging. Are you sure the internet is not open on those PC's? Sounds like some kinda spyware or trojan hammering the internet.
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pjtemplinCommented:
Ha!  You haven't seen my counters.  The OP is doing well to get his T1 to 98% usage; my fractional T1 customers will start a download of any form and drop ~100 packets.  Feeding a 384k or 768k pipe from 2x100M uplinks means the output queue will jump up until TCP can slow things down.
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