> I expect SIP server not to challenge SIP Client again, either for > refresh REGISTER or de-REGISTER. Is this expectation as per standards?. > (I am assuming that nonce value used by server is not expired.) > > What is the reason for repeated challenge by server ?
Yes; it is valid and can occur for a verity of reasons. The following are a few potential reasons that might apply to specific server. 1) Server considers the nonce stall or disagrees on the nc value. 2) Similar to number 1, the server only allows single use nonces within all or some situations for security reasons. 3) RFC 3261 and other documentation could be improved concerning reusing nonces (with higher nc) across transactions (standalone, calls, and subscriptions) associated with an outbound server (proxy/B2BUA/...). 4) Similar to prior reasons, the server might only maintains a limited number of such outstanding nonces for the user and/or server. _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
