Re: [rtcweb] DTLS, DTLS-SRTP, and 5-tuples

Cullen Jennings <fluffy@cisco.com> Mon, 09 March 2015 17:48 UTC

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From: Cullen Jennings <fluffy@cisco.com>
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Date: Mon, 9 Mar 2015 09:28:23 -0600
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To: Jonathan Lennox <jonathan@vidyo.com>
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Subject: Re: [rtcweb] DTLS, DTLS-SRTP, and 5-tuples
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> On Mar 5, 2015, at 8:22 AM, Jonathan Lennox <jonathan@vidyo.com> wrote:
> 
> 
> On Mar 5, 2015, at 5:14 AM, Roman Shpount <roman@telurix.com> wrote:
> 
>> On Thu, Mar 5, 2015 at 4:52 AM, Iñaki Baz Castillo <ibc@aliax.net> wrote:
>> 2015-03-05 7:58 GMT+01:00 Christer Holmberg <christer.holmberg@ericsson.com>om>:
>> > As far as I understand, sending of multiple ClientHellos, on different
>> > 5-tuples, would require a change to core DTLS (not only DTLS-SRTP), and who
>> > knows how long such work would take. Do we really want to add such
>> > dependency to our deliveries at this point?
>> 
>> Sorry, I think I didn't explain well.
>> 
>> It is not about multiple DTLS connections, but about the fact that
>> DTLS packets belonging to the *same* DTLS connection/association can
>> be carried over different 5-tuples. This may happen during agressive
>> ICE nomination in which media (so the DTLS ClientHello) follows the
>> USE-CANDIDATE Binding request without even waiting for a response.
>> 
>> When was it agreed that DTLS ClientHello can be sent before the connectivity check succeeded? I understand that this will increase the connection setup time, but I though that no data should be sent before the connectivity check response (consent) from the remote party.
> 
> As I understand the current rough consensus, the endpoint has to have received a successful response to a connectivity check on the 5-tuple, proving consent, but it doesn’t have to have received (or sent) a check with a USE-CANDIDATE attribute in it yet.
> 
> This was the outcome of our discussion “merging" regular and aggressive ICE nomination.

That matches my understanding of how things work.