Re: [tram] Points that should be clarified in STUN-bis and TURN-bis

Simon Perreault <simon.perreault@viagenie.ca> Fri, 07 February 2014 21:50 UTC

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Date: Fri, 07 Feb 2014 16:50:05 -0500
From: Simon Perreault <simon.perreault@viagenie.ca>
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Subject: Re: [tram] Points that should be clarified in STUN-bis and TURN-bis
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Le 2014-02-07 16:19, Oleg Moskalenko a écrit :
> Well... OK. If we want the client always to send the address-family -
> but we do not enforce that on the receiving side... that sounds
> awkward,  like a speed limit without cops. It is great - but does that
> strict requirement make sense without enforcement ? We can always say
> that TURN client SHOULD send the address-family, but MUST probably would
> be too strict... I guess.

The idea is: first, we specify that TURN bis clients MUST send
REQUESTED-ADDRESS-FAMILY. Then we specify TURN bis server behaviour
depending on the value of REQUESTED-ADDRESS-FAMILY. We do *not* specify
TURN bis server behaviour when that parameter is absent. If the
parameter is absent, the client is not following the TURN bis spec, and
the server is free to behave however it wants. That includes *wink wink*
being backward-compatible with TURN.

This is exactly like the STUNv2 magic cookie: STUNv2 clients MUST send
the magic cookie, and STUNv2 server behaviour is defined when the cookie
is present. But STUNv2 does not specify server behaviour when the cookie
is absent. The cookie being absent means the client is not a STUNv2
client. The server is free to behave however it wishes. That includes
*wink wink* being backward-compatible with STUNv1.

Simon
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