[Asterisk-Users] ip phones and intercom/paging

[Siggi Langauf]

On Sat, 9 Aug 2003, John Todd wrote:

> >The Ciscos should be able to do this via a XML Service using the RTPTx:
> >and RTPRx: URI schemes. The tricky part is just pushing the RTPRx to the
> >listening phone.
> >
> >XML service specifications are here:
> >http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_administration_guide09186a008018e234.html
>
> I don't think this is possible, from my understanding of the Cisco
> firmware using SIP images.  While it may be possible to initiate
> receipt of an RTP stream from an XML command, how do you get the
> Cisco to execute the XML command to begin with, without having the
> user push keys to start up the process?  Caution: to not believe the
> Cisco manuals are correct when they say that the SIP O/S on the phone
> runs a web server.  They do not.

Really??
Well, the Skinny version does run a web server. Maybe an upgrade of the
SIP firmware comes with that feature?

>  The only way that I have discovered
> the Cisco 79xx phones can download a URL from a remote server are via
> either user interaction (pressing a sequence of keys) or by putting
> together a really UGLY XML page that "refreshes" every few seconds.
> But even this suffers from the problem of: "How does the first page
> get requested?"

The phones have an "idle URL" setting, which can be used exactly for that:
polling an XML service every n seconds. However, I admit that's ugly.

> I'd be happy to be proven wrong in my assertion that intercom and
> paging is impossible with Cisco SIP phones.  Please send code.  :)

Will do, as soon as I get time to play with this. That's way at the bottom
of my todo list, though...

> Now, if all your comments are about SCCP phones, can you send along
> the SCCP driver for Asterisk so the rest of us can play?

Well, sorry. For now, you'll have to use CCM and configure * as an H.323
gateway using chan_oh323.
Writing a Skinny driver is definitely somethinh I will not do. I'd happily
move away from that protocol, if they'd just let me...

Maybe the MGCP firmware is an alternative?

> PS: If one could initiate XML requests remotely, perhaps a better way
> to do intercom/paging would be to use the "Play" command, and (if
> possible) use a pipe on the server side to connect to a live audio
> stream.  (sigh) If only I could control the phones from the server...

Nope, the "play" command (whatever you mean by that: there's playing a
file via TFTP, and playing audio/basic via HTTP) won't work properly for
that purpose: The phone would just download the whole stream before
playing it (in both cases). That means you get an initial delay >= length
of stream, and the stream is limited by the phone's memory (to 5s
according to the documentation, to 20s acording to my experiments...).

	Siggi