[Asterisk-Users] iax2 wireless and Multicast

[Francisco Pérez Botella]

El Miércoles, 4 de Enero de 2006 12:28, tim panton escribió:
> On 3 Jan 2006, at 19:10, Francisco Pérez Botella wrote:
> > Hi.
> >
> >
> > I will have to manage From asterisk to clients IP-phones, so biefly
> > the idea
> > is to multiplex voip flows in large packets and multicast them from
> > asterisk/AP to client stations. flows from client stations to asterisk
> > gateway go unicast. I wonder how iax2 protocol will be good for
> > multiplex
> > (trunk) and multicast ??
>
> Hmm, it won't be easy.
> The IAX protocol is not multicast aware, so it is expecting a single
> ack to each
> full frame.  You will have to do quite a bit of work on the IAX
> implementation
> for it to do the right thing in that area.
I see, maybe I could redirect at network layer unicast-->multicast 
addresses/group and give back a "false" single ack at that point.
On the other side (client side). I need some like a "virtual trunk" where each 
station recieves the full frame and "stealth" the payload it needs for the 
user/phone(s) it serves. I could at client station redirect traffic from 
multicast to unicast interface address and serve the full frame to iax2 at 
client station, silently dropping the acks they give back.

>
> I'm also not sure I see the advantage of multicast, given that normally
> phone calls are 1 to 1 connections, (except conferences I suppose).

That maybe true for wired but wireless in infraestructure mode there's a point 
of distribution (the AP) that even can police and pool in a pseudo TDM, I 
mean all the traffic in the subnet is going to pass trought that point

> Is it a packet size problem ?

It's a capacity problem first, it's an avoidance of collisions too.
wireless is a shared medium (radio) and minimizing overhead without latency
penalty will be important. I think that in a radio system broadcast is for 
free capacity and overhead is not. 
>
> http://www.westhawk.co.uk/

-- 
Francisco J. Pérez Botella