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RE: VoIP QOS best practices

  • From: Charles Youse
  • Date: Mon Feb 10 17:35:05 2003

But in order for RTP to resync the out-of-order packets it must introduce some delay, no?
And that delay causes issues.

C.

-----Original Message-----
From: Stephen Sprunk [mailto:stephen@sprunk.org]
Sent: Monday, February 10, 2003 5:21 PM
To: Leo Bicknell
Cc: North American Noise and Off-topic Gripes
Subject: Re: VoIP QOS best practices



Reordering per se doesn't affect VoIP at all since RTP has an inherent
resync mechanism.

Reordering is also unlikely, since each packet is sent 20ms or more apart;
I'm not aware of any network devices that reorder on that scale.

S

----- Original Message -----
From: "Leo Bicknell" <bicknell@ufp.org>
Sent: Monday, 10 February, 2003 12:43
Subject: Re: VoIP QOS best practices


> - --OXfL5xGRrasGEqWY
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>
> In a message written on Mon, Feb 10, 2003 at 01:19:08PM -0500, chaim fried
=
> wrote:
> > happens). There is no reason to implement QOS on the Core. Having said
> > that, there still seems to be too many issues on the tier 1 networks
> > with pacekt reordering as they affect h.261/h.263 traffic.=20
>
> I've got a question about this issue.  Many networks reorder packets
> for a number of reasons.  At least once before I've attempted to
> measure the effects of this reordering on a number of forms of
> traffic, but I have never understood the particular effects on VOIP
> traffic.
>
> Indeed, the two times I was asked to investigate this for video
> people it turns out the video receivers /had no ability to handle
> out of order frames/.  That's right, get one packet out of order
> and the video stream goes away until it resynchronizes.  Now, I
> realize reordering should not happen to a large percentage of the
> packets out there, but it also seems to me any IP application has
> to handle reordering or it's not really doing IP.
>
> So what's the real problem here?  Are the VOIP boxes unable to
> handle out of order packets?  Do the out of order packets simply
> arrive far enough delayed to blow the delay budget?  What percentage of
> reordered packets starts to cause issues?
>
> - --=20
>        Leo Bicknell - bicknell@ufp.org - CCIE 3440
>         PGP keys at http://www.ufp.org/~bicknell/
> Read TMBG List - tmbg-list-request@tmbg.org, www.tmbg.org
>
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