[asterisk-biz] SIP Fax OK?

[Matthew Rubenstein]

On Tue, 2007-08-07 at 13:38 -0400, Andrew Joakimsen wrote:
> On 8/6/07, Matthew Rubenstein <email at mattruby.com> wrote:
> >         According to Xorcom's press release advertising their reliable Asterisk
> > Fax/ZAP solution
> > ( http://www.xorcom.com/documentation/white_papers/fax_modem ), the
> > problem Asterisk has with mediating faxes is Zaptel timer desync
> > problems. So does that mean that Asterisk can reliably receive and send
> > faxes when connected to the PSTN by SIP (or IAX) to a gateway switch?
> > --
> >
> 
> Yes, if all the SIP endpoints support ITU-T Recommendation T.38. The
> problem is there is no such thing right now in Asterisk and no plans
> by Digium to add it.
> 
> If you have a SIP provider supporting T.38 then you can have calls
> from your T.38 capable devices forwarded to that provider, but you
> must use Asterisk 1.4 and pray it works.

	Thanks for the clear, concise - and quick - reply. I think my followup
is more appropriate to the -users list, but I don't understand the
protocol for crossposting, or somehow notifying the readers of this
thread in this -biz list that I'm jumping. I'll repost there if asked or
advised.

	What does the SIP provider (SIP/PSTN gateway) have to do to support
T.38? Is it just a question of all their gear between their TDM network
and the SIP gateway supporting T.38? Or do their operations have to do
anything extra to support it, other than buying the right routers and
enabling the right configs when deploying those routers?

	Also, the current T.38 "SIP Passthru" support in Asterisk means that
Asterisk can connect two other SIP hosts (or two connections to eg. a
single SIP/PSTN gateway host) that are carrying a call whose media
content is just fax data, correct? But can't do anything but connect
those endpoints (eg, save the fax on the Asterisk HD). But can that call
be recorded to Asterisk HD with the fax data intact, or can extra legs
(muted) be connected to a "fax conference" that feeds multiple receiving
(POTS) faxes with the same incoming fax call data?
-- 

(C) Matthew Rubenstein