On Tue, 2009-01-20 at 11:51 +0100, Iñaki Baz Castillo wrote: > Hi, RFC 4235 states that each NOTIFY about a dialog(s) must increment > the "version" field value, the the recipient must ignore notifications > with no incremented "version" numbers. > I wonder why this mechanism is needed, is not enough with CSeq? The > NOTIFY is part of a dialog and there is already a mechanism to control > de sequential requests order (CSeq header). > > Isn't this "version" field a redundant solution? Is it really needed? > (perhaps I miss something...).
There is no assurance that there are not other requests being send on the same dialog as the NOTIFY, and there are also "retry" situations (e.g., needing to refresh an authorization nonce) that can cause the notifier to send NOTIFYs that do not reach the subscriber. So a gap in the series of received CSeq values does not indicate that a needed NOTIFY was not delivered. The "version" value, being contained in the NOTIFY body, does not have these deficiencies. Dale _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
