Subject: RE: [Sip] draft-ietf-sip-sips-03.txt: Closing of Opened issues

From: [email-masked] (Juha Heinanen)
Date: Thu, 26 Apr 2007 23:23:47 +0300

Francois Audet wrote:

  We've been through this already. You know that a UAC supports TLS by
  the fact that it used TLS to register. It's the "implicit
  indication". 

UAC does not need to register in order to be able to SEND requests.  

so UAC sends initial request over tls via its proxy (an possibly other
proxies) to UAS and then bye comes from the UAS 2 hours later.  how does
the proxy know that it should forward bye to UAC over tls if there is no
transport=tls parameter anywhere?

-- juha

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From: Dean Willis <[email-masked]>
Date: Thu, 26 Apr 2007 16:13:36 -0500

> transport=tls parameter anywhere?

We have the assumption that if TLS can be used, it will be used.  
Under this model, if a proxy doesn't know whether a UAS supports TLS  
or not, it needs to run through the discovery process to find out  
whether it does.

Don't like the overhead of probing? Then either use appropriate DNS  
records, or link to an outbound proxy that uses them, or just use a  
SIPS contact for everything.

--
Dean

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From: [email-masked] (Juha Heinanen)
Date: Fri, 27 Apr 2007 09:28:01 +0300

> We have the assumption that if TLS can be used, it will be used.

again "we" != "real world".  it is much easier and faster to use
transport=tls parameter in r-r header than doing rediscovery or probing
when bye arrives.

may it is high time to write a "real world" BCP document that help to
identify things that are broken in official ietf documents and that "we"
refuses to recognize.

-- juha