On Fri, May 30, 2008 at 9:59 AM, <[EMAIL PROTECTED]> wrote: > Hi, > Considering that both UAC and UAS support Session Timer. > If UAC sends an INVITE request with the refresher parameter set as 'uas' > in the Session-Expires header, the UAS has to have Session-Expires > header with the refresher parameter set to 'uas'. > Now when the UAS sends an UPDATE, what will the refresher parameter be > in the Session Expires header?considering the fact that the UAS of the > initial transaction is actually acting as the UAC for the current > Transaction(sending UPDATE).
The meaning of the refresher parameter applies to the direction of the current transaction. It is irrelevant whether the entity generating a refresh request was a UAC or a UAS in a previous transaction. In your example, if the entity generating UPDATE wants to remain the refresher then it should put refresher=uac in the UPDATE. > Will the refresher parameter mean the 'uas' of initial transaction or > will it keep changing with every Transaction? Putting referesher=uas in the UPDATE means that the current UAC (the entity that is sending the UPDATE) wants the recipient of the UPDATE to be the refresher. Here is a quote from section 7.4 of RFC 4028 that describes how this works -- If the session refresh request is not the initial one, it is RECOMMENDED that the refresher parameter be set to 'uac' if the element sending the request is currently performing refreshes, and to 'uas' if its peer is performing the refreshes. This way, the role of refresher does not change on each refresh. However, if it wishes to explicitly change the roles, it MAY use a value of 'uas' if it knows that the other side supports the session timer. It could know this by having received a request from its peer with a Supported header field containing the value 'timer'. If it seeks to reselect the roles, it MAY omit the parameter. -- Raj Jain _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
