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

"Worley, Dale R (Dale)" <> Mon, 06 June 2011 19:10 UTC

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From: "Worley, Dale R (Dale)" <>
To: Peter Musgrave <>, "Shekh-Yusef, Rifaat (Rifaat)" <>
Date: Mon, 6 Jun 2011 15:07:29 -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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From: [] On Behalf Of Peter Musgrave []

I have concerns about this approach. Fundamentally the RTP stream is not symmetric (in the sense of RFC4961). This has consequences for NAT traversal, general interoperability and media path security schemes like ZRTP.

I have to agree and disagree...  As Rifaat diagrammed it, the call should work, as it uses already-defined SIP facilities.  Indeed, it's rather clever, I'd never thought of joining a sendonly dialog with a recvonly dialog.  There are some limitations, in that we depend on the far-end UA to execute the join in the way we want.

The problems you raise, those of asymmetric RTP, already exist -- One can make a sendonly audio call, or a recvonly audio call.  We need to ensure that NAT traversal and ZRTP work correctly when  media stream is set up to be one-way.