[Asterisk-Dev] Re: Instability with H323

[Peter Nixon]

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- --snip--
> > Thus, if the encoded audio frames are sent by asterisk, or by openh323,
> >   there is no different to the packet size.
> >
> > What you will find is that openh323 will put 3 gsm audio frames into one
> > ethernet packet. This gives a bandwidth of 20kbit/sec
> >
> > Asterisk will put 1 gsm audio frame into one ethernet packet. This will
> > lead to a bandwith of over 30kbit/sec.
>
> Using large frames-per-packet values is not so much pretty as could seen
> due to increased packetization delays (total of algorithmic and
> packetization delays for 1 frame/packet is about 20 ms but for 3
> frames/packet is about 60 ms). Also, long frames requires to have longer
> (it time dimension) jitter buffers and loosing of long packets is much more
> sensitive for earth than loosing short packets.
>
> Also, I don't think passing additional 10 kbps for 100 Mbit/s network is so
> significant.

Ahem.. Thats nice for you to only have to think about using Asterisk on 
Ethernet, however unfortunately some of us are out in the "real 
world" (substitute "third world" if you prefer) and don't have the luxury.

Unfortunately, in my part of the world, "standard" cable internet costs approx 
$55/month for 128kbps/33kbps. This means for me (or my customers) to use VoIP 
at all from home the upload _must_ use less than 33kbps

Added to that, the international fiber links are regularly saturated which 
means that all my "commercial" VoIP gateways have either a direct satellite 
dish, or (even worse) a Frame Relay link to a satellite dish.

For carrying calls on these types of links, I am sorry to say that my 6 year 
old "Clarent Media Gateway" is still an order of magnitude more efficient 
than Asterisk, as is any standard Cisco VoIP gateway.
I have very high hopes for Asterisk however assuming Ethernet connections to 
VoIP gateways completely ignores probably 90% of VoIP users in the world.

To repeat, 10kbps is ALOT of data to me, as it is exactly 30% of the entire 
upstream bandwidth from the greater percentage of my customers!

Regards

- -- 

Peter Nixon
http://www.peternixon.net/
PGP Key: http://www.peternixon.net/public.asc
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