Difference between negative and positive discarded packets

[Anonymous]

Greetings,

I am troubleshooting some incoming call quality issues for a customer and I am seeing a number of out of ourder packets being displayed when using the 'show voice quality statistics' command.  I am seeing both positive and negative numbers listed for the "out of order" section and I would like to know the difference between negative numbers and positive numbers in this column. Any help would be greatly appreciated in understanding the lingering call quality issues.

Adtran# show voice quality-stats

         Start                                                                      Out of  Discard   Delay
ID       Time     From       To                        Length Codec  Order    Pkts*  Avg   Max
--------------------------------------------------------------------------------

4476     1:34 PM  0000000000 0000000000 60:41  G711u  -3188   4678    99    100
4477     1:34 PM  0000000000 0000000000 0:09   G711u  0       0       90    90
4478     1:35 PM  0000000000 0000000000 59:39  G711u  -2593   3936    99    100
4479     1:56 PM  0000000000 0000000000 0:38   G711u  0       0       90    90
4480     2:01 PM  0000000000 0000000000 49:02  G711u  -2306   2869    99    100
4482     2:26 PM  0000000000 0000000000 0:12   G711u  0       0       90    90
4483     2:26 PM  0000000000 0000000000 1:49   G711u  75      10      95    100
4484     2:38 PM  0000000000 0000000000 3:08   G711u  -72     118     92    100
4485     2:39 PM  0000000000 0000000000 19:17  G711u  -2330   2596    96    100
4476     1:34 PM  0000000000 0000000000 60:41  G711u  -3188   4678    99    100
4477     1:34 PM  0000000000 0000000000 0:09   G711u  0       0       90    90
4478     1:35 PM  0000000000 0000000000 59:39  G711u  -2593   3936    99    100
4479     1:56 PM  0000000000 0000000000 0:38   G711u  0       0       90    90
4480     2:01 PM  0000000000 0000000000 49:02  G711u  -2306   2869    99    100
4482     2:26 PM  0000000000 0000000000 0:12   G711u  0       0       90    90
4483     2:26 PM  0000000000 0000000000 1:49   G711u  75      10      95    100
4484     2:38 PM  0000000000 0000000000 3:08   G711u  -72     118     92    100
4485     2:39 PM  0000000000 0000000000 19:17  G711u  -2330   2596    96    100

[Anonymous]

Zero80,

Thanks for posting!  If you haven't already found it, the guide Understanding Call Quality Statistics in AOS has helpful information regarding the interpretation of these values.  Specifically, it defines out of order packets as "The number of packets received that did not match the expected sequence number."  Since this statistic is based on the RTP sequence number being received, it would appear that something out of the normal with the RTP sequence numbers for these calls.  This might have been triggered by a SIP Re-Invite, a transfer, hold, etc that caused a large jump forward or backward in the sequence number.  A packet capture of the call may help us determine what is causing the negative value.

Having said that, Adtran has done significant work to improve the accuracy of the voice quality stats output in R10.5.0 firmware.  I would suggest that you upgrade this unit to the highest R10.5.x version available on our website, http://www.adtran.com.  If you are already on that version, we would need to get the packet capture to determine why we have these negative values. 

Lastly, I'm also concerned about your average delay getting close to maximum delay on most calls.  This typically indicates a high level of jitter within the inbound audio stream.  This often indicates a QoS problem in the network.  Feel free to respond to this post if you have further questions.

Thanks!

David

[Anonymous]

Zero80.

I just wanted to check back with you on this.  Did you have any further questions I can answer?  Just let me know if I can provide any further assistance.

Thanks!

David

[Anonymous · Accepted solution]

Hi David,

Thanks for the information.  We were able to resolve the issue by double checking QoS further upstream. I had always suspected it was QoS related but the negative out of order packets threw me off and I was not sure if that was a bug or not.

Thanks again.

[Anonymous]

Zero80,

I went ahead and flagged the "Correct Answer" on this post to make it more visible and help other members of the community find solutions more easily. If you don't feel like the answer I marked was correct, feel free to come back to this post and unmark it and select another in its place with the applicable buttons.  If you still need assistance, we would be more than happy to continue working with you on this - just let us know in a reply.

Thanks,

David