Hi All,
We are developing IMS core network nodes esp. CSCF. I have a query related to implementation of RFC 4028 especially w.r.t. 3GPP TS 24.229 and 3GPP TS 32.260 procedures. 1. As per 3GPP TS 24.229 - When the P-CSCF receives from the UE an INVITE request, the P-CSCF may require the periodic refreshment of the session to avoid hung states in the P-CSCF. If the P-CSCF requires the session to be refreshed, then the P-CSCF shall apply the procedures described in RFC 4028 clause 8. This clause says "When the current time equals or passes the session expiration for a session, the proxy MAY remove associated call state, and MAY free any resources associated with the call. Unlike the UA, it MUST NOT send a BYE". 2. Now, consider a case when UAC, P-CSCF1, S-CSCF2 and P-CSCF2 don't support but SCSCF1 and UAS support session refreshment. On timer expiry UAS doesn't generate a BYE and SCSCF1 removes its respective call context. In such a case how will UAC, P-CSCF1, S-CSCF2 and P-CSCF2 release their hung states??? 2. On session expiration will S-CSCF1 send any trigger towards charging data function (on Diameter)??? If yes, there are various AVPs which might not get filled. 3. As per 3GPP TS 32.260 charging data function starts an interim timer when it expects Account charging request from Charging trigger function at CSCF nodes. What is correlation between this timer and session refreshment timer? 4. The header Min-SE has been defined to avoid unnecessary load of session refreshment at proxies. Proxy can decide the maximum rate at which it wants to receive the Session refreshment request. The headers Session-Expires and Min-SE are checked only in requests. Consider a case when UAC is a 'refresher' and UAS decreases the value of session expires to a very low value in response. In responses the proxies are not supposed to check the session expiry timer, so effectively the purpose of Min-SE (that's to avoid unnecessary load) gets defeated. In such a scenario, in my opinion proxies should be allowed to modify these headers in response also. Finally, my question is how important is to implement this RFC, as even in the current telecom systems there are facilities for audits which run at regular intervals and clear the hung states of the call. Can anybody provide tell me at which mailing list should I pose the queries related to 3GPP TS IMS procedures? Dushyant P S Dhalia _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
