What Does Pct Mean?

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Asterisk Users 9 Comments

Hello,

could somebody please tell me the meaning of “Pct” as seen in asterisk cli:

………..Receive……… ………Transmit………. Count Lost Pct Jitter Count Lost Pct Jitter RTT….

Thanks, Michael

9 thoughts on - What Does Pct Mean?

  • Hi Carsten,

    Are you sure? I’m seeing here:

    ………..Receive……… ………Transmit………. Count Lost Pct Jitter Count Lost Pct Jitter RTT….
    188K 0 0 0.000 188K 16641K 8809 0.000 0.026

    => This doesn’t sound reliable to me: there are 188K packets and 16641K
    of them are lost?! The Pct value is fluctuating between about 6009 and 9009.

    Thanks, Michael

  • No you’re reading it wrong.

    There are 188K received with no loss, and 16441K transmitted.

    Still 8809 does not sound like a percentage to me

  • This doesn’t make any sense to me, either. There can’t be more packages transmitted than received. It’s the same codec in and out and it’s been running exactly the same time.

    ^^^^ ^^^^
    There are 188K received and 188K transmitted. Pct is unknown – what’s Pct?

  • Lost and Percent (pct) are not calculated by counting packets. Those are calculated from the sequence numbers in the RTP frame.

    For example let’s say you start the receiver (Asterisk) at Sequence
    #1….then something happens and it jumps to sequence #5000. The audio might be fine, but now the stats say 4998 packets were lost. Why is there a bizarre sequence jump? Hard to say. I have seen it because of bugs that eventually get fixed on the CPE, or even when there is a change of codec (or re-invite) mid-call. I would not worry too much about this unless you can reproduce it and can address it properly at the CPE level. A packet capture will clearly confirm what I am referring to here. Just look at every Sequence # in the RTP flow and you will see the jump.


    Technical Support

  • Could this gap in sequence numbers caused by a codec change generate errors like the one below?

    [2018-02-13 12:57:43] WARNING[4917][C-0004c2cb] codec_sangoma.c:
    [526559][g722toulaw] Got Seq 15944 but expecting 10106 (time since last read = 0ms), dropped 5838 packets

  • Um, I may be missing something here, but if it was “percent”, wouldn’t it simply be the internationally recognised symbol for percent, the, um, percent symbol? %

    That’s why I don’t think it can be percent.

  • codec and forgets what sequence number it was on (or something like that). The two ends might not notice any audio issues however. Having said that, I have seen other PBXs that choke on something like this and most often drop the call completely when this happens.


    Technical Support http://www.cellroute.net

  • 16641/188 = 8852% is not quite 8809% but I suspect it is just a rounding issue. Of couse it makes no sense to lose more than 100% but this is just a math formula. I don’t think there are any checks in the asterisk code to make sure the result of the math operation makes sense.

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