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Re: VoIP QOS best practices
From: "Stephen J. Wilcox" <steve () telecomplete co uk>
Date: Mon, 10 Feb 2003 19:13:47 +0000 (GMT)


On Mon, 10 Feb 2003, Leo Bicknell wrote:

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. 
<snip> 
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?

You have two choices

Drop them - you either have gaps in the stream or the codec allows for gaps and 
reconsutrcts small missing sections (buffer to do this)

Reorder them - fine, but you need to buffer, we want to minimise delay so how 
long do you want to wait, what delay is acceptable on top of the other delays we 
have as well.. (same outcome as jitter)

As to what percentage is a problem, that depends on which of the two above ways 
you are using and how much delay you want. Or in the drop it scenario how many 
missing frames cause the speech to become degraded.

Steve


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