>>IMHO a proxy CANNOT add a Require option tag, can it? it can but it is bit of a hack. RFC4028 itself does not recommend it. However it allows it to try to force a session timer even if the request originator does not support it. with the value 'timer', the proxy MAY insert a Require header field with the value 'timer' into the request. However, this is NOT RECOMMENDED. This allows the proxy to insist on a session timer for the session. This header field is not needed if a Supported header field was in the request; in this case, the proxy would already be sure the session timer can be used for the session. If "unsupported: timer" is returned, the UA, as you say, won't understand it. But it's of no consequence, the UA can't do anything anyway. The Unsupported response is for a user to try to understand why the request failed - if it failed due to "unsupported: timer", then the user can conclude that an upstream proxy inserted the "timer" requirement (but RFC4028 knowledge is required - not ideal I suppose). Regards, Attila
________________________________ From: [EMAIL PROTECTED] on behalf of Iñaki Baz Castillo Sent: Wed 01/10/2008 19:30 To: sip-implementors@lists.cs.columbia.edu Subject: Re: [Sip-implementors] SIP Proxy inserting Option Tags El Miércoles, 1 de Octubre de 2008, Victor Pascual Ávila escribió: > RFC3261 > 20.32 Require > The Require header field is used by UACs to tell UASs about options > that the UAC expects the UAS to support in order to process the > request. > > RFC4028 > 8.1. Processing of Requests > the proxy MAY insert a Require header field with the value 'timer' > into the request. > > Is a SIP proxy allowed to insert Option tags when forwarding a > request? In that case, why "Require" is preferred than "Supported" in > RFC4028? I don't understand how a proxy can add a "Require" option tag. Let me explain the issue with an example: - A sends INVITE to B through proxy P. - P adds "Require: xxxx". - B replies "420 Bad Extension". - "420" arrives to P who forwards it to A. - So A receives the "420" with a header "Unsupported: xxxx". - A didn't add that option tag so it doesn't understand what happened. IMHO a proxy CANNOT add a Require option tag, can it? -- Iñaki Baz Castillo _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
