Re: [MMUSIC] draft-holmberg-mmusic-sdp-dtls-00

[Roman Shpount <[e-mail]>]

On Wed, Jun 17, 2015 at 1:52 PM, Paul Kyzivat <[e-mail]> wrote:

>
> I'd also like to dig a bit more into forking. As noted in section 4.5, if
> forking occurs, then separate DTLS associations will be made with each
> callee. In this case, those distinct DTLS associations will share common
> host candidates. (Can they also end up sharing some relay candidates?) Yet
> the 5-tuples will differ.
>

The 5-tuples would typically be different and that should be enough for
de-mux. Sharing the same host or relay candidates should not be a problem.

One thing to keep in mind, would be that if allocation of new relay
candidates is done before the exciting relay candidates are released, then
new relay candidates will be different. If relay candidates are released
before allocation, then relay candidates can end up being the same, which
can cause problems. Relay candidates that were closed due to being unused
by previous ICE session, can be reused since no existing DTLS traffic would
be flowing over them. The same closing order restriction also applies to
the host candidates. Otherwise if you release local host candidates before
allocating new one, you might end up with the same local address/ports
combinations.


> Now, suppose that the same endpoint then needs to make a change. For
> instance, maybe it needs to change its fingerprint. In this case it needs
> to create new DTLS associations. In that case it must also use new host
> candidates. Is it permitted to use the same (new) candidates to recreate
> *both* DTLS associations? I can't see any reason why not. I also don't see
> any specific prohibition in the text. But it would be good to be explicit
> about it.
>

If I understand what you are asking, It is possible to use the same host
candidates to update multiple DTLS associations that are created due to
forking. The only requirement is that when DTLS association is updated, the
set of host and related candidates (relay, reflexive) is new for
communications within this specific m= line on connection to this specific
end-point. The end goal is to create a new 5-tuple. This being said, such
usage would be fairly uncommon.

_____________
Roman Shpount