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Re: Fwd: I-D ACTION:draft-zimmermann-avt-zrtp-03.txt
"Christer Holmberg \(JO/LMF\)" <christer.holmberg@xxxxxxxxxxxx> writes:
>>>We need to remember that media will not always be end-to-end. You may
>>>have SBCs, transcoders, media mixers etc, in the path which will
>>>terminate media. I don't think that is covered in requirements.
>>It's not mentioned in the requirements.
>I think it would be an extremely important requirement to have.
>Otherwise you may end up with a solution which is useless in many
>real-life deployments, where these types of intermediate nodes exist.
>So, I think a requirement should say something like:
>Rx: A solution MUST work when there are intermediate nodes, terminating
>or processing media, between the endpoints.
Classic (and *extremely* common) example: B2BUA's such as Asterisk
(sort-of; it's not a perfect B2BUA, but is likely to improve). Devices
such as that are likely to be a pretty common case, even ignoring SBCs and
the like. At minimum they should be addressed in the spec and their effect
understood and agreed to.
>>>>Note that those systems won't work with ICE, either.
>>If those systems don't have exceptions for DTLS-SRTP, RTP header
>extensions, or ZRTP packets, it isn't too likely they
>>have extensions for ICE, either...
>And, even if they do recognize ICE, in ICE it is possible to encapsulate
>media inside STUN packages (unless it has recently been changed), so in
>addition these nodes would have to be able to inspect what's inside the
>STUN packages in order to determine whether they are used for
>(signalling or media encapsulation).
My bet is that their support for ICE is much more likely than DTLS or ZRTP,
and more likely than hdrext's. But that's just my bet.
>>Without a list of requirements, we cannot make progress.
>>From your statement above, I believe your requirement is:
>> A solution MUST NOT expect packets to be received on the
>> media path until 200 OK, because the media path will be
>> blocked by middleboxes until the 200 OK.
>>Is that an accurate description of the requirement?
>You could say "MAY be blocked by middleboxes", though.
Randell Jesup, Worldgate (developers of the Ojo videophone), ex-Amiga OS team
"The fetters imposed on liberty at home have ever been forged out of the weapons
provided for defence against real, pretended, or imaginary dangers from abroad."
- James Madison, 4th US president (1751-1836)