Re: [rtcweb] Tunnelling DTLS in SDP

On Tue, Apr 5, 2016 at 2:53 AM, Harald Alvestrand <harald@alvestrand.no>
wrote:

> On first read, this makes sense to me.
>
> I wonder if it could/should be made into a general concept, to fit with
> the tendency in WebRTC:NG to separate signalling format even more from
> operation?
>
> We could call it "out of band DTLS setup", say that in general, a DTLS
> session can be started in one medium (SDP signalling, in this case), and
> continued in another medium (the DTLS-protected media channel), and have a
> section describing the details of carrying DTLS-over-SDP.
>

> When viewing it in this way, using the same technique with Jabber or
> proprietary signalling becomes a reasonably obvious exercise. There are
> some other twists that seem obvious too - for instance, one could continue
> the setup over the SDP channel in subsequent offer/answers if the first
> exchange failed to set up a media channel. I'm not sure that makes sense,
> though.
>

In ORTC language, we could simply have an event on the DtlsTransport that
is something like .onpacket and another that's .addpacket, and when the
transport wants to send a packet, it lets the JS know so it can do so over
the signalling path, and then the JS can take care of optimizing it (or
not).

>
> One SDP twist: If forking happens, it could be treated like any other
> attempt to generate multiple answers to a ClientHello, I think. I'm sure
> it's well defined how to respond to that - it's an obvious attack. Only one
> leg of the fork would ever succeed, I assume.
>
>
>
> On 04/04/2016 03:10 PM, Eric Rescorla wrote:
>
> Hi folks,
>
> I wanted to call your attention to a draft I just published with a
> possibly stupid
> idea.
>
> https://tools.ietf.org/html/draft-rescorla-dtls-in-sdp-00
>
> A nontrivial fraction of call setup time in WebRTC is the DTLS handshake.
> This document describes how to piggyback the first few handshake messages
> in the SDP offer/answer exchange, thus reducing latency.
>
> Comments welcome.
>
> -Ekr
>
>
>
>
>
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