Subject: RE: [Sipping] RFC3263 SIPS URI transport selection

From: "Frank Shearar" <[email-masked]>
Date: Mon, 21 Feb 2005 16:26:31 -0000

Dean Willis wrote:
> 
> On Feb 18, 2005, at 3:47 AM, Frank Shearar wrote:
> 
> > RFC 3263 says this at the beginning of section 4.1:
> >
> >    If the URI specifies a transport protocol in the transport 
> > parameter,
> >    that transport protocol SHOULD be used.
> >
> >    Otherwise, if no transport protocol is specified, but 
> the TARGET is 
> > a
> >    numeric IP address, the client SHOULD use UDP for a SIP 
> URI, and TCP
> >    for a SIPS URI.
> >
> > My question is regarding the "and TCP for a SIPS URI" bit: 
> shouldn't 
> > this be "and TLS over TCP" or something? Or "a secure reliable 
> > transport" even?
> >
> > It seems to me that by saying "and TCP for a SIPS URI" that the RFC 
> > regards it as acceptable for a SIP entity to send this 
> message over an 
> > insecure link. That can't be right, so what have I missed?
> 
> There was a some argument about this when we were working on the text 
> for 3263. It went something like "TCP and UDP are "transport" 
> protocols. TLS is a mechanism for securing TCP connections. So the 
> transport is TCP, even for SIPS, and saying TLS is a 
> transport would be 
> incorrect. So let's say TCP here, and elsewhere define that 
> TLS MUST be 
> used as a protection mechanism when the URI is a a sips: type."

Ah OK, I thought it might have been this. What confused me is that we write Via headers as "SIP/2.0/TLS foo.com" when using TLS-over-TCP.

Thanks for the answer!

frank

*******************************************************************
This email and attachments (if any) must be swept for viruses before opening. Their contents may be confidential or privileged and are intended solely for the named recipient. If you are not the intended recipient and you have received this email in error you must not read or use this email and should notify RNID on: +44 (0) 20 7296 8282.

RNID, Registered Office 19-23 Featherstone Street, London EC1Y 8SL No. 454169 (England, Registered Charity No. 207720)

********************************************************************

_______________________________________________
Sipping mailing list  https://www1.ietf.org/mailman/listinfo/sipping
This list is for NEW development of the application of SIP
Use [email-masked] for questions on current sip
Use [email-masked] for new developments of core SIP