VoIP QOS best practices

Mon Feb 10 19:21:50 UTC 2003

G.711 gives you the 64kbps quality you get on a channel in a PRI line.
No compression is performed.

G.729 is a well accepted codec that performs compression, and with ip
packet overhead, uses about 16 to 24 kbps (can't remember which).  It
gives voice quality very close to G.711.

G.723 has a noticeable voice quality change, and is in the 6 to 8 kbps
range.

The optimal is G.729 for quality vs bandwidth issues. 

There are some other considerations involved but these are the main
ones.

Ray Burkholder

> -----Original Message-----
> From: Charles Youse [mailto:cyouse at register.com] 
> Sent: February 10, 2003 14:42
> To: Alec H. Peterson
> Cc: nanog at nanog.org
> Subject: RE: VoIP QOS best practices
> 
> 
> 
> Speaking of codecs, what are the primary variables one uses 
> when choosing a codec?  I imagine this is some function of 
> how much bandwidth you want to use versus how much CPU to 
> encode the voice stream.
> 
> C.
> 
> -----Original Message-----
> From: Alec H. Peterson [mailto:ahp at hilander.com]
> Sent: Monday, February 10, 2003 1:40 PM
> To: Bill Woodcock; Charles Youse
> Cc: nanog at nanog.org
> Subject: RE: VoIP QOS best practices
> 
> 
> --On Monday, February 10, 2003 10:19 -0800 Bill Woodcock 
> <woody at pch.net> 
> wrote:
> 
> >
> > It works fine on 64k connections, okay on many 9600bps 
> connections.  T1 is
> > way more than is necessary.
> 
> I'd say that largely depends on which codec you are using and 
> how many 
> simultaneous calls you will have going.
> 
> Alec
> 
> --
> Alec H. Peterson -- ahp at hilander.com
> Chief Technology Officer
> Catbird Networks, http://www.catbird.com
> 