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

[Kevin P. Fleming]

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).

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 :-)