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Re: VoIP QOS best practices
From: "Stephen Sprunk" <stephen () sprunk org>
Date: Mon, 10 Feb 2003 16:17:51 -0600


You are mistaking utilization for congestion.  At the packet level, a link
is congested if it is not immediately available for transmit due to one or
more previous packets still being queued/transmitted.  This transient
congestion causes jitter, VoIP's worst enemy.

Certainly, as utilization rises so will congestion; however, it is quite
common to have transient congestion while overall utilization is minimal.

S


----- Original Message -----
From: "Shawn Solomon" <ssolomon () ind net>
Sent: Monday, 10 February, 2003 12:54
Subject: RE: VoIP QOS best practices


If you are in an environment where the uplink is already saturated, or
nearly so, QOS is necessary.  But QOS only discards packets in times of
contention.  So, if you don't have contention, you don't need it.  IF
you have 300 people and 4meg of data all fighting for that t1, it makes
a world of difference.


- -----Original Message-----
From: Bill Woodcock [mailto:woody () pch net]=20
Sent: Monday, February 10, 2003 1:28 PM
To: Charles Youse
Cc: nanog () nanog org
Subject: RE: VoIP QOS best practices


    > But I could conceivably have 10+ voice channels over a T-1, I
still
    > don't quite understand how, without prioritizing voice traffic,
the
    > quality won't degrade...

Well, of course it all depends how much other traffic you're trying to
get
through simultaneously.  Your T1 will carry ~170 simultaneous voice
streams with no conflict, but you have to realize that they'll stomp on
your simultaneous TCP data traffic.  But you don't need to protect the
_voice_...

Look, just do it, and you'll see that there aren't any problems in this
area.

                                -Bill

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