[asterisk-dev] Direct media in the new SIP work

[Mark Michelson]

Hi devs,

I have been tasked with implementing direct media support in the new SIP 
work for Asterisk 12. I'm appealing to the dev list to find out if there 
are any direct media-related features that are not in current Asterisk 
but that would fit well in the new version of Asterisk.

As a refresher, direct media refers to Asterisk's ability to send 
reinvites to endpoints involved in an established two-party bridge so 
that the endpoints will send media directly to one another instead of 
sending through Asterisk.

Here's a brief rundown of the configuration options available for direct 
media in Asterisk 11:

* directmedia=yes/no to enable/disable direct media per SIP peer
* a directmedia=nonat option to only allow direct media if a media NAT 
is not in effect.
* a directmedia=outgoing option to only send direct media reinvites on 
outgoing call legs (used to mitigate reinvite glare scenarios)
* a directmedia=update option to send SIP UPDATE requests instead of 
reinvites in order to set up direct media.
* direct media ACLs to prevent a peer from using direct media if they 
have registered from an address where direct media would not be 
permissible/possible.

Something to keep in mind for this discussion is that I'm only looking 
at the SIP side of direct media here. As far as the RTP layer and 
bridging APIs are concerned, I'm not going to touch them. What I'm more 
interested in here are features relating to configuration of direct 
media for SIP endpoints and signaling enhancements beyond what Asterisk 
already offers.

Note that directrtpsetup is a completely different beast from 
directmedia, and I'd like to avoid discussion of it for the moment 
since, if we implement that at all in the new SIP work, it will be done 
at a later time.

Let me hear your thoughts on the matter.

Mark Michelson