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This Question is Not Answered 1 Correct Answer available (4 pts) 2 Helpful Answers available (2 pts)
3076 Views 3 Replies Latest reply: Oct 16, 2008 9:29 PM by Phosphorivera RSS

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delay is more predictable

Oct 16, 2008 1:06 AM

Phosphorivera 31 posts since
Sep 24, 2008

Dear QoS Expert,

 

My question is base on QoS Student Guide Page 1-13.

According the last line of this page written that "By minimizing delay, you can also reduce jitter (delay is more predictable)". I though that the delay is not predictable. Does it mean that the delay hopefully predictable or any other meaning about this?

Thank you for your kind support guys!

  • Conwyn 7,914 posts since
    Sep 10, 2008
    Currently Being Moderated
    1. Oct 16, 2008 1:25 AM (in response to Phosphorivera)
    Re: delay is more predictable

     

    This may be a definitional issue.

     

     

    I think delay is the time it takes to cross the network. These are defined within the Service Level Agreement if it exists. On the Internet there is sometimes a SLA if you only access sites within that Internet Service Provider. Generally they say 99% will arrive within X ms. For example X might be 300ms

     

     

    Consider the SLA is always achieved the first UDP packet takes 200ms , the second 150 and the third 250 so they could arrive out of sequence or more likely with a small gap before the second and a long gap before the third. So the voice messages speeds up and slows down. This is normal called jitter because it is jitterly. This is solved by using a jitter buffer.

     

     

    Regards Conwyn

     

     

  • Conwyn 7,914 posts since
    Sep 10, 2008
    Currently Being Moderated
    3. Oct 16, 2008 10:52 PM (in response to Phosphorivera)
    Re: delay is more predictable

     

    Hi Phosphorus

     

     

    It is explained better than I by http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a00800945df.shtml

     

     

    See the playout-delay keyword. I assume it is a function of the DSP (PVDM2-x).

     

     

    Regards Conwyn

     

     

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