[55792] in North American Network Operators' Group
Re: VoIP QOS best practices
daemon@ATHENA.MIT.EDU (Stephen J. Wilcox)
Mon Feb 10 18:23:56 2003
Date: Mon, 10 Feb 2003 23:23:15 +0000 (GMT)
From: "Stephen J. Wilcox" <steve@telecomplete.co.uk>
To: Petri Helenius <pete@he.iki.fi>
Cc: Stephen Sprunk <stephen@sprunk.org>,
Leo Bicknell <bicknell@ufp.org>,
North American Noise and Off-topic Gripes <nanog@merit.edu>
In-Reply-To: <01dc01c2d156$f03f7b40$932a40c1@PHE>
Errors-To: owner-nanog-outgoing@merit.edu
On Tue, 11 Feb 2003, Petri Helenius wrote:
>
> >
> > Reordering per se doesn't affect VoIP at all since RTP has an inherent
> > resync mechanism.
>
> Most VoIP implementations donīt care about storing out-of-order packets
> because they think that 20ms or 30ms late packets should be thrown
> away in any case.
> >
> > 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.
> >
> Most "core" routers, at least from vendors C and J have enough packet
> memory to keep packets for hundreds of milliseconds. Apply sufficent
Really.. including many Gigabit, OC-12,48 interfaces
> per packet load balancing (which would be stupid but doable) to this,
> and youīll arrive at the end result.
And its unlikely you will be doing this therefore..
>
> Our observations tell us that reordering does not happen too much but
> there are periods from a few minutes to an hour where reordering from
> specific ASīs skyrocket to return to normal, in many cases even without
> observable path change. (MPLS in action?)
>
> Pete
>
>
