Serial Interface Queues/Buffers & Voice Traffic

f.sorrentino · ‎11-02-2013

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

Joseph W. Doherty · ‎11-02-2013

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 · ‎11-04-2013

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 · ‎11-04-2013

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.