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Serial Interface Queues/Buffers & Voice Traffic

Unanswered Question
Nov 2nd, 2013
User Badges:

Hi All,


Looking for a bit of assistance in understanding why I continue to get drops on the serial interface although the buffer is not full.  This circuit carries both voice and data and the issue is hissing sound at certain times during voice calls but only in one direction. The hissing occurs at the RX of the TX traffic showing below.


From the checking done it looks like the hissing only occurs at peak usage times.  There are no drops on the policy map far any voice payload traffic (EF bit).


I tried increasing the output queue but I am still getting drops and some hissing.  The default class is the one that is dropping most as expected I wouldnt have expected this to interfere with the Voice.


The voice is using MGPC and VAD is currently disabled on the lines i have tested.


Serial1/2 is up, line protocol is up

  Hardware is M8T-X.21

  Description: |xxxxxx |

  MTU 1500 bytes, BW 896 Kbit/sec, DLY 20000 usec,

     reliability 255/255, txload 248/255, rxload 178/255

  Encapsulation FRAME-RELAY, crc 16, loopback not set

  Keepalive set (10 sec)

  Restart-Delay is 0 secs

  LMI enq sent  0, LMI stat recvd 0, LMI upd recvd 0

  LMI enq recvd 169, LMI stat sent  169, LMI upd sent  0, DCE LMI up

  LMI DLCI 1023  LMI type is CISCO  frame relay DCE

  FR SVC disabled, LAPF state down

  Broadcast queue 0/64, broadcasts sent/dropped 252/0, interface broadcasts 0

  Last input 00:00:02, output 00:00:00, output hang never

  Last clearing of "show interface" counters 00:28:06

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 51261

  Queueing strategy: Class-based queueing

  Output queue: 687/4096/64/1268 (size/max total/threshold/drops)

     Conversations  54/160/256 (active/max active/max total)

     Reserved Conversations 6/6 (allocated/max allocated)

     Available Bandwidth 256 kilobits/sec

  30 second input rate 626000 bits/sec, 354 packets/sec

  30 second output rate 874000 bits/sec, 278 packets/sec

     534848 packets input, 115252830 bytes, 0 no buffer

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

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

     415235 packets output, 184284733 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



Serial1/2 is up, line protocol is up

  Hardware is M8T-X.21

  Description: | xxxxx |

  MTU 1500 bytes, BW 896 Kbit/sec, DLY 20000 usec,

     reliability 255/255, txload 249/255, rxload 152/255

  Encapsulation FRAME-RELAY, crc 16, loopback not set

  Keepalive set (10 sec)

  Restart-Delay is 0 secs

  LMI enq sent  0, LMI stat recvd 0, LMI upd recvd 0

  LMI enq recvd 180, LMI stat sent  180, LMI upd sent  0, DCE LMI up

  LMI DLCI 1023  LMI type is CISCO  frame relay DCE

  FR SVC disabled, LAPF state down

  Broadcast queue 0/64, broadcasts sent/dropped 270/0, interface broadcasts 0

  Last input 00:00:05, output 00:00:00, output hang never

  Last clearing of "show interface" counters 00:29:59

  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 55938

  Queueing strategy: Class-based queueing

  Output queue: 842/4096/64/1429 (size/max total/threshold/drops)

     Conversations  49/160/256 (active/max active/max total)

     Reserved Conversations 6/6 (allocated/max allocated)

     Available Bandwidth 256 kilobits/sec

  30 second input rate 536000 bits/sec, 285 packets/sec

  30 second output rate 877000 bits/sec, 207 packets/sec

     568280 packets input, 123045479 bytes, 0 no buffer

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

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

     439783 packets output, 196694215 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


Checked the active calls for lost/late packets and there was some but it was not incrementing.


Bibby_Topaz_Off#sh call active voice | in Late|Lost

RxLatePak=20

LateDiscardDuration=520

LostPackets=297

LatePackets=20

RxLatePak=0

LateDiscardDuration=0

LostPackets=106

LatePackets=0

RxLatePak=4

LateDiscardDuration=160

LostPackets=106

LatePackets=4

RxLatePak=0

LateDiscardDuration=0

LostPackets=0

LatePackets=0

Bibby_Topaz_Off#


Any ideas how I can omit this hissing?


I didnt post this in a Voice forum as Its more related to the WAN but admin pls advise if it needs to be reposted.


Cheers

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Joseph W. Doherty Sat, 11/02/2013 - 17:58
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Disclaimer


The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.


Liability Disclaimer


In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.


Posting


Just increasing buffers can be counter productive.


For good VoIP performance, you might need to downsize your serial interface's FIFO buffers.


If the bandwidth is down near half a T1, you might also need to concern yourself with serial delay caused by large packets.


If using frame-relay, you may need to concern yourself with exceeding CIR.


PS:

It might be helpful if you described the QoS policy (with it stats), the platform, the IOS version, and the WAN topology.

f.sorrentino Mon, 11/04/2013 - 01:23
User Badges:

Hi Joseph,


The serialzation delay is a factor I was aware of,   however at the moment I am trying to ascertain the source of the hissing   and seeing in what ways I can affect it to better understand how to   resolve it.


I have since set the frag size to 1120bytes.


Hardware is as follows:

Cisco 7206VXR - Version 12.4(12.2r)T

and

C2801-ADVENTERPRISEK9-M), Version 12.4(24)T3



below is the policy-map


policy-map XXXXX-out

class Voice

    priority 256

class Voice_signal

    bandwidth 32

class Network_Control

    bandwidth 32

class cl-XXXX_RDP

    bandwidth 64

class cl-XXXX_email

    bandwidth 64

class video

    bandwidth 256

class PVC_801

    bandwidth 128

   police rate 128000  burst 24000

     conform-action transmit

     exceed-action drop

     violate-action drop

class class-default

    fair-queue

     random-detect dscp-based


There are no drops on the voice policy map.  The only drops are on the default class.    


Cisco 2801 Policy-map


  Service-policy output: XXXXXX-out


    queue stats for all priority classes:

      Queueing

      queue limit 64 packets

      (queue depth/total drops/no-buffer drops) 0/0/0

      (pkts output/bytes output) 1297537/39664389


    Class-map: HCC_Voice (match-any)

      1297537 packets, 87378823 bytes

      30 second offered rate 0 bps, drop rate 0 bps

      Match: ip dscp ef (46)

        1296560 packets, 87325028 bytes

        30 second rate 0 bps

      Match: ip dscp cs5 (40)

        977 packets, 53795 bytes

        30 second rate 0 bps

      Match: ip precedence 5

        0 packets, 0 bytes

        30 second rate 0 bps

      Priority: 192 kbps, burst bytes 4800, b/w exceed drops: 0



    Class-map: Voice_signal (match-any)

      43889 packets, 4939488 bytes

      30 second offered rate 0 bps, drop rate 0 bps

      Match: ip dscp cs3 (24)

        12889 packets, 848951 bytes

        30 second rate 0 bps

      Match: ip dscp af31 (26)

        28392 packets, 3773238 bytes

        30 second rate 0 bps

      Match: access-group name HCC_Voice_signal

        2608 packets, 317299 bytes

        30 second rate 0 bps

      Queueing

      queue limit 64 packets

      (queue depth/total drops/no-buffer drops) 0/0/0

      (pkts output/bytes output) 43889/4720556

      bandwidth 12 kbps


    Class-map: Network_Control (match-any)

      345732 packets, 76081039 bytes

      30 second offered rate 30000 bps, drop rate 0 bps

      Match: access-group name Net-Man-TCP

        169 packets, 25778 bytes

        30 second rate 0 bps

      Match: access-group name Net-Man-UDP

        343595 packets, 75933541 bytes

        30 second rate 30000 bps

      Match: access-group name Net-Man-ICMP

        1969 packets, 121720 bytes

        30 second rate 0 bps

      Match: ip dscp cs2 (16)

        0 packets, 0 bytes

        30 second rate 0 bps

      Queueing

      queue limit 64 packets

      (queue depth/total drops/no-buffer drops) 1/0/0

      (pkts output/bytes output) 345558/30903934

      bandwidth 32 kbps


    Class-map: cl-XXX_RDP (match-any)

      0 packets, 0 bytes

      30 second offered rate 0 bps, drop rate 0 bps

      Match: access-group name Topaz_RDP.acl

        0 packets, 0 bytes

        30 second rate 0 bps

      Queueing

      queue limit 64 packets

      (queue depth/total drops/no-buffer drops) 0/0/0

      (pkts output/bytes output) 0/0

      bandwidth 64 kbps


    Class-map: cl-Topaz_email (match-any)

      15812 packets, 12127777 bytes

      30 second offered rate 0 bps, drop rate 0 bps

      Match: access-group name XXX_email.acl

        15812 packets, 12127777 bytes

        30 second rate 0 bps

      Queueing

      queue limit 64 packets

      (queue depth/total drops/no-buffer drops) 0/0/0

      (pkts output/bytes output) 15812/12209077

      bandwidth 64 kbps


    Class-map: video (match-any)

      3302143 packets, 1945992540 bytes

      30 second offered rate 273000 bps, drop rate 0 bps

      Match: access-group name Video_Streamer.acl

        3302143 packets, 1945992540 bytes

        30 second rate 273000 bps

      Queueing

      queue limit 64 packets

      (queue depth/total drops/no-buffer drops) 0/0/0

      (pkts output/bytes output) 3302143/1955179296

      bandwidth 256 kbps


    Class-map: HCC_PVC_801 (match-any)

      2968327 packets, 1215625538 bytes

      30 second offered rate 238000 bps, drop rate 110000 bps

      Match: fr-dlci 801

        2968327 packets, 1215625538 bytes

        30 second rate 238000 bps

      Queueing

      queue limit 64 packets

      (queue depth/total drops/no-buffer drops) 0/11/0

      (pkts output/bytes output) 2687092/867372197

      bandwidth 128 kbps

      police:

          rate 128000 bps, burst 24000 bytes, peak-burst 1500 bytes

        conformed 2687103 packets, 863091284 bytes; actions:

          transmit

        exceeded 2144 packets, 1500371 bytes; actions:

          drop

        violated 279080 packets, 351033883 bytes; actions:

          drop

        conformed 127000 bps, exceed 0 bps, violate 110000 bps


    Class-map: class-default (match-any)

      6023661 packets, 961004793 bytes

      30 second offered rate 206000 bps, drop rate 0 bps

      Match: any

      Queueing

      queue limit 64 packets

      (queue depth/total drops/no-buffer drops/flowdrops) 34/9364/0/0

      (pkts output/bytes output) 6020849/956793738

      Fair-queue: per-flow queue limit 16

        Exp-weight-constant: 9 (1/512)

        Mean queue depth: 4 packets

        dscp     Transmitted       Random drop      Tail/Flow drop Minimum Maximum Mark

                  pkts/bytes    pkts/bytes       pkts/bytes    thresh  thresh  prob


        default  9268038/1550306823   9433/2695490     4975/1430562           20            40  1/10

        cs1         1016/44704           1/44             0/0                 22            40  1/10

        cs6        48252/14344408        5/1928          20/3889              32            40  1/10



Cisco 7206 Policy


Service-policy output: xxxx-out


    Class-map: Voice (match-any)

      1216027 packets, 86258303 bytes

      30 second offered rate 0 bps, drop rate 0 bps

      Match: ip dscp ef (46)

        1201091 packets, 82956286 bytes

        30 second rate 0 bps

      Match: ip dscp cs5 (40)

        2950 packets, 1359797 bytes

        30 second rate 0 bps

      Match: ip precedence 5

        11986 packets, 1942220 bytes

        30 second rate 0 bps

      Queueing

        Strict Priority

        Output Queue: Conversation 264

        Bandwidth 256 (kbps) Burst 6400 (Bytes)

        (pkts matched/bytes matched) 1155315/39965127

        (total drops/bytes drops) 3785/426151


    Class-map: Voice_signal (match-any)

      29711 packets, 5645243 bytes

      30 second offered rate 0 bps, drop rate 0 bps

      Match: ip dscp cs3 (24)

        27186 packets, 3732244 bytes

        30 second rate 0 bps

      Match: ip dscp af31 (26)

        816 packets, 482054 bytes

        30 second rate 0 bps

      Match: access-group name Voice_signal

        1709 packets, 1430945 bytes

        30 second rate 0 bps

      Queueing

        Output Queue: Conversation 265

        Bandwidth 32 (kbps)Max Threshold 64 (packets)

        (pkts matched/bytes matched) 26602/5199084

        (depth/total drops/no-buffer drops) 0/2/0


    Class-map: Network_Control (match-any)

      313309 packets, 50840867 bytes

      30 second offered rate 6000 bps, drop rate 0 bps

      Match: access-group name Net-Man-TCP

        274 packets, 11623 bytes

        30 second rate 0 bps

      Match: access-group name Net-Man-UDP

        312780 packets, 50812954 bytes

        30 second rate 6000 bps

      Match: access-group name Net-Man-ICMP

        250 packets, 16000 bytes

        30 second rate 0 bps

      Match: ip dscp cs2 (16)

        5 packets, 290 bytes

        30 second rate 0 bps

      Queueing

        Output Queue: Conversation 266

        Bandwidth 32 (kbps)Max Threshold 64 (packets)

        (pkts matched/bytes matched) 290022/47098892

        (depth/total drops/no-buffer drops) 0/125/0


    Class-map: cl-XXX_RDP (match-any)

      0 packets, 0 bytes

      30 second offered rate 0 bps, drop rate 0 bps

      Match: access-group name Topaz_RDP.acl

        0 packets, 0 bytes

        30 second rate 0 bps

      Queueing

        Output Queue: Conversation 267

        Bandwidth 64 (kbps)Max Threshold 64 (packets)

        (pkts matched/bytes matched) 0/0

        (depth/total drops/no-buffer drops) 0/0/0


    Class-map: cl-XXX_email (match-any)

      14072 packets, 6517726 bytes

      30 second offered rate 0 bps, drop rate 0 bps

      Match: access-group name email.acl

        14072 packets, 6517726 bytes

        30 second rate 0 bps

      Queueing

        Output Queue: Conversation 268

        Bandwidth 64 (kbps)Max Threshold 64 (packets)

        (pkts matched/bytes matched) 13760/6498419

        (depth/total drops/no-buffer drops) 0/2/0


    Class-map: cl-XXX_video (match-any)

      2792 packets, 309302 bytes

      30 second offered rate 0 bps, drop rate 0 bps

      Match: access-group name Video_Streamer.acl

        2792 packets, 309302 bytes

        30 second rate 0 bps

      Queueing

        Output Queue: Conversation 269

        Bandwidth 64 (kbps)Max Threshold 64 (packets)

        (pkts matched/bytes matched) 2494/277100

        (depth/total drops/no-buffer drops) 0/0/0


    Class-map: XXX_PVC_801 (match-any)

      3954518 packets, 3134064278 bytes

      30 second offered rate 428000 bps, drop rate 299000 bps

      Match: fr-dlci 801

        3954518 packets, 3134064278 bytes

        30 second rate 428000 bps

      Queueing

        Output Queue: Conversation 270

        Bandwidth 128 (kbps)Max Threshold 64 (packets)

        (pkts matched/bytes matched) 2210108/891923945

        (depth/total drops/no-buffer drops) 0/1489/0

      police:

          rate 128000 bps, burst 24000 bytes, peak-burst 24000 bytes

        conformed 2346289 packets, 904275343 bytes; actions:

          transmit

        exceeded 889 packets, 1087608 bytes; actions:

          drop

        violated 1605356 packets, 2228008911 bytes; actions:

          drop

        conformed 127000 bps, exceed 0 bps, violate 299000 bps


    Class-map: class-default (match-any)

      5613369 packets, 4578138675 bytes

      30 second offered rate 754000 bps, drop rate 2000 bps

      Match: any

      Queueing

        Flow Based Fair Queueing

        Maximum Number of Hashed Queues 256

        (total queued/total drops/no-buffer drops) 620/73347/55837

         exponential weight: 9


   dscp    Transmitted      Random drop      Tail drop    Minimum Maximum  Mark

           pkts/bytes       pkts/bytes       pkts/bytes    thresh  thresh  prob

   af11      49/3968            0/0              0/0           32      40  1/10

   af12       0/0               0/0              0/0           28      40  1/10

   af13       0/0               0/0              0/0           24      40  1/10

   af21       0/0               0/0              0/0           32      40  1/10

   af22       0/0               0/0              0/0           28      40  1/10

   af23       0/0               0/0              0/0           24      40  1/10

   af31       0/0               0/0              0/0           32      40  1/10

   af32       0/0               0/0              0/0           28      40  1/10

   af33       0/0               0/0              0/0           24      40  1/10

   af41       0/0               0/0              0/0           32      40  1/10

   af42       0/0               0/0              0/0           28      40  1/10

   af43     177/54195           0/0              0/0           24      40  1/10

    cs1   26226/28299502        8/10237          0/0           22      40  1/10

    cs2       0/0               0/0              0/0           24      40  1/10

    cs3       0/0               0/0              0/0           26      40  1/10

    cs4       0/0               0/0              0/0           28      40  1/10

    cs5       0/0               0/0              0/0           30      40  1/10

    cs6     257/15420           0/0              0/0           32      40  1/10

    cs7       0/0               0/0              0/0           34      40  1/10

     ef       0/0               0/0              0/0           36      40  1/10

   rsvp       0/0               0/0              0/0           36      40  1/10

default 5561215/4529061026   8814/9458679     8687/8465984     20      40  1/10

Joseph W. Doherty Mon, 11/04/2013 - 01:52
User Badges:
  • Super Bronze, 10000 points or more

Disclaimer


The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.


Liability Disclaimer


In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.


Posting


It might still be helpful if you would describe the WAN topology.


Could you clarify what it means when you set frag size to 1120?  Are you using MLPPP?


BTW, your 7200, I believe, is pre-HQF QoS and your 2801 is post-HQF QoS.


As to "hissing", you might move this thread (or post a new question) on the VoIP forum.

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