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RE: VoIP QOS best practices

  • From: chaim fried
  • Date: Mon Feb 10 16:16:28 2003

Good point. Later version from the larger video-conferencing Gateway
manufacturers, seem to do a better job (better- not perfect) handling
reordering. So clearly there seems to have been issues with the
applications buffering itself. Out of order packets are considered lost,
so whatever you would put your tolerance threshold for loss will
determine your tolerance for ou of sequence? I would measure in terms of
.0x% for my customers, who expect "toll-quality" video.  

Based on the traces we've examined, most of the time it's not that the
latency is too much to be rectified with proper buffering. However,
again we don't want anybody reordering our packets.

> -----Original Message-----
> From: Leo Bicknell [] 
> Sent: Monday, February 10, 2003 11:44 AM
> To:
> Subject: Re: VoIP QOS best practices
> 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.
> 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?
> -- 
>        Leo Bicknell - - CCIE 3440
>         PGP keys at
> Read TMBG List -,

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