[asterisk-dev] Implementing Paging on the Linksys SPA9XX phones

[John Lange]

On Wed, 2006-05-17 at 13:32 -0500, Kevin P. Fleming wrote:
> John Lange wrote:
> 
> > In any case, even if this is non-trivial I believe the effort would be
> > well worth it to finally have a "real" paging system in Asterisk. I have
> > a feeling some other SIP phone makers would also incorporate this method
> > into their firmware if it was supported.
> 
> Other SIP phone manufacturers already support multicast using the
> traditional SIP/SDP model (no 'special' multicast packets like
> Cisco/Linksys use).

Can you give examples of which phones? I don't know what you mean by the
SIP/SDP model and google on those terms didn't turn up anything
meaningful with regard to paging.

> The bigger issue, though, is that applications in Asterisk are
> completely unaware of the channel types they are running on (generally).
> This means that the Page application can't generate 'multicast RTP',
> since it has no idea whether RTP is even in use or not (and it may be in
> use on some channels in the paging group and not others). Any solution
> will require finding a way to abstract a group of phones listening
> (only) to the same audio stream and learning whether they support
> multicast or not... not trivial, as I said :-)

It may be as simple as specifying what type of "paging" a given device
supports (if any) in the config files for the device. If a given device
is then included in a page group then asterisk would handle each device
in its own way.

So for example; SIP phones which only support paging because one of
their lines is set to auto-answer (like the ciscos) can be one setting;
phones that support multi-cast linksys style is another; SIP/SDP yet
another; and so on.

We are very interested in solving this issue because paging seems to be
the most often asked for feature in Asterisk that doesn't really exist.

-- 
John Lange