Re: [splices] Using Two Separate Devices to Start a Conversation proposal

"Worley, Dale R (Dale)" <> Mon, 06 June 2011 19:52 UTC

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From: "Worley, Dale R (Dale)" <>
To: Alan Johnston <>
Date: Mon, 6 Jun 2011 15:49:12 -0400
Thread-Topic: [splices] Using Two Separate Devices to Start a Conversation proposal
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Subject: Re: [splices] Using Two Separate Devices to Start a Conversation proposal
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> If I understand correctly, there will be two separate RTP streams,
> two m= lines?

There will be two m= lines, but it is one m= line in one dialog, and
another m= line in the other dialog.

> If this is the case, then two separate NAT traversal mechanisms will
> be used (i.e. ICE rubs twice or two relays used). As far as ZRTP or
> other media path keying protocols, each session will be keyed
> separately. With ZRTP the endpoint will see two different ZIDs.
> This does unfortunately mean two Diffie Hellman calculations.

I think the envisioned problem is with simpler NAT traversal
mechanisms which do not use ICE, but rather depend on the RTP packets
traveling "out" through the NAT to establish and maintain an inward
mapping "pinhole".  That won't work with one-way media, or rather,
inward-only media.

> Since these are separate sessions, each will have an RTCP session as
> well, and these may need NAT traversal as well.

> So this will work, but things like logging and quality reporting
> will be quite complicated.

Hmmm...  In this case, they won't be any harder than they would be in
a three-way ad-hoc conference call.