Subject: [MMUSIC] ICE-tcp issue: TURN shim vs. RFC 4571 shim

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 09 Jul 2007 16:28:38 -0400

It occurred to me that the TURN TCP shim (which allows for a type in 
addition to a length) might be a better choice for muxing STUN and 
application data over ice-tcp connections. RIght now, the RFC4571 shim 
is used, which provides only a length. The application data and STUN are 
demuxed based on the magic-cookie and other fields like FINGERPRINT, 
once they are extracted from the rfc4571 shim. This is not a 
deterministic demux, though it works with extremely high probability.

But why not make it easy? If we just use the TURN framing, its 
deterministic. This would also eliminate the usage of two different 
framing protocols (one for the connection from the client to its turn 
server, and the other for ice-tcp run through that turn server). In fact 
we could move the turn framing into rfc3489bis and mandate it for usage 
with STUN over TCP, covering TURN and ICE.

I don't see any technical drawbacks to this, except for it being a change.

-Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Cisco Fellow                                   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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From: Rémi Denis-Courmont <[email-masked]>
Date: Wed, 11 Jul 2007 10:28:38 +0300

> deterministic demux, though it works with extremely high probability.

By the way, does RFC4571 work with DTLS(-SRTP) along with STUN? I know it 
works with SRTP, and I know it works with STUN and RTP, but what about DTLS, 
STUN and (S)RTP at the same time? Does the first two bits trick still work?

If it does not, there is little questioning TURN shim should be used rather 
than Framed RTP.

In any case, I'd tend to favor using RFC4571 only without STUN (incl. w/o ICE) 
and only TURN shim with STUN (incl. with ICE) from an implementation 
perspective.

-- 
Rémi Denis-Courmont