Re: [rtcweb] I-D Action: draft-ietf-rtcweb-data-protocol-01.txt

[Paul Kyzivat <[e-mail]>]

Comment at end.

On 10/29/13 11:28 AM, Eric Rescorla wrote:
>
> On Tue, Oct 29, 2013 at 8:23 AM, Paul Kyzivat <[e-mail]
> <mailto:[e-mail]>> wrote:
>     On 10/27/13 5:45 AM, Randell Jesup wrote:
>         On 10/26/2013 6:30 PM, Paul Kyzivat wrote:
>
>                 My proposal has three elements, which together can
>                 guarantee that
>                 there are no stream id allocation conflicts between peers:
>                      1. The browser and application select stream ids
>                 based on initial
>                 SDP offerer/answerer role rather than DTLS role (e.g.,
>                 initial
>                 offerer uses even ids, initial answerer uses odd ids).
>                 With this
>                 rule, the offering application knows its role
>                 immediately without
>                 waiting for the DTLS or SDP handshake to occur.
>
>             A similar issue has come up in the discussion of partial
>             offers/answers. (Regarding how to assign a=mid values.) And
>             a similar
>             solution was proposed.
>
>             It was then rejected on the basis that sometimes both "ends"
>             think
>             they are offerers or answerers. This comes about as a result of
>             signaling-only B2BUAs that play games with O/A on two legs.
>
>         Exactly why we went with DTLS roles.
>
>     I'm not sure this eliminates the problem.
>
>     Is it not possible for an intermediary on the signaling path to
>     insert itself in the media path, manipulating the SDP such that the
>     two ends both establish the DTLS with the intermediary?
>
> There is a separate role negotiation for DTLS (actpass, etc.) that works
> even if both sides think they are the offerer or answerer.

I know about that. That mechanism is also used for TCP negotiation in 
SDP. And that is one place where an intermediary sometimes sticks its 
nose in explicitly to manipulate the roles, allowing both ends to be active.

In the current case, ICE and possible TURN result in getting the media 
path established without those games. So maybe there is less motivation 
for an intermediary. But still, they still seem to show up because 
administrators think they need them. And once there, couldn't the 
intermediary still end up making both ends think they are active?

	Thanks,
	Paul