[Asterisk-Users] frames/packet

[Andres]

We have customers all over the world on our SIP Services (not Asterisk Based).  
We have found the optimal setting to be 60ms on the phones (using G729).  
This consumes about 14kbps of bandwith per call.  The added delay is quite 
acceptable and customers often tell us that the voice quality is much better 
than international PSTN lines.  We did ask Martin a while back if it could be 
implemented in * as a config option.  Hopefully it will be at some point in 
the future.

Regards,
Andres
http://www.telesip.net

On Wednesday 03 September 2003 13:26, Paul Lambert wrote:
> Steve Underwood wrote:
> > Paul Lambert wrote:
> > >"Not yet." implies that it is coming.
> >
> > Look at the latency it causes, and you will see its not that useful.
> >
> > >I know it would help on Internet
> > >connections such as fixed wireless and cable modem where packet rate is
> > >an issue. 20ms translates to 50 packets/sec.
> >
> > 30ms per block codec aren't bad. Going beyond that gets nasty. 2 x 20ms
> > blocks per packet about the most people will tolerate.
>
> 2 x 20ms cuts the packet rate in half. That means a fixed wireless ISP
> could fit twice the calls on a single access point.
>
> > >I believe cable modem
> > >upstream packet rates cap at 150-200 packets/sec. G729 gets the bit rate
> > >down to 8kbits.
> >
> > G.729 gets the rate down to 8kbps. Then RTP puts it back up to several
> > times that.
> >
> > >So based on a bit rate of 256K the theory is that the
> > >link could handle 32 calls. But, that would produce packets coming out
> > >at a rate of 1600 packets/sec beyond the limitation of most Internet
> > >connections including a T1.
> >
> > A T1 has no particular packet limit. It is just limited to 1544kbps.
> > Some routers choke on large numbers of small packets, but that is not a
> > T1 problem.
>
> There has to be a limit. You can't send 1 bit packets. As I think about
> it more, I'm sure it's higher than 1600 packets/sec probably closer to
> 3000 packets/sec. So with 20ms blocks/packet your limit on a T1 with IP
> would be 60 calls. Go 2 x 20ms and then you get 120 calls all with the
> same IP overhead. I think an extra 20ms latency could be worth it.
>
> > Regards,
> > Steve
> >
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