[SIPForum-discussion] SIP UAS Behavior

[Yip, Sam SH]

Hello,

 

I have an argument for session timer.

 

The scenario is UAC requests session timer in the Invite message and indicate
the refresher is UAC. Must UAS includes the Require header with value "timer"
in the 2xx response?

 

I read the RFC 4028. UAS must provide Require header. However, someone told
me the part in section 9 is additional explanation for case 4 in table 2. So
if the case is 5, Require header is optional.

 

        UAC supports?  refresher parameter  refresher parameter

                           in request           in response

       -------------------------------------------------------

             N                none                 uas

             N                uac                  NA

             N                uas                  NA

             Y                none             uas or uac

             Y                uac                  uac

             Y                uas                  uas

 

                        Table 2:  UAS Behavior

 

   The fourth row of Table 2 describes a case where both the UAC and UAS

   support the session timer extension, and where the UAC did not select

   who will perform refreshes.  This allows the UAS to decide whether it

   or the UAC will perform the refreshes.  However, as the table

   indicates, the UAS cannot override the UAC's choice of refresher, if

   it made one.

   If the refresher parameter in the Session-Expires header field in the

   2xx response has a value of 'uac', the UAS MUST place a Require

   header field into the response with the value 'timer'.

 

Many thanks.

Sam

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