Hi The importance of CSeq in REGISTER is for the proper ordering of REGISTER request which shall be used by registrar to update the bindings. The expected response from the registrar in the below mentioned case shall be 500 response. Please refer section 10.3 of RFC 3261 for further explanation.
The section 10.3 of RFC 3261 states that Point 7 -"For each address, the registrar then searches the list of current bindings using the URI comparison rules. If the binding does not exist, it is tentatively added. If the binding does exist, the registrar checks the Call-ID value. If the Call-ID value in the existing binding differs from the Call-ID value in the request, the binding MUST be removed if the expiration time is zero and updated otherwise. If they are the same, the registrar compares the CSeq value. If the value is higher than that of the existing binding, it MUST update or remove the binding as above. If not, the update MUST be aborted and the request fails. This algorithm ensures that out-of-order requests from the same UA are ignored. Each binding record records the Call-ID and CSeq values from the request. The binding updates MUST be committed (that is, made visible to the proxy or redirect server) if and only if all binding updates and additions succeed. If any one of them fails (for example, because the back-end database commit failed), the request MUST fail with a 500 (Server Error) response and all tentative binding updates MUST be removed." regards Abhishek Dhammawat Aricent -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of cool goose Sent: Monday, February 23, 2009 11:00 PM To: [email protected] Subject: [Sip-implementors] CSeq header field in Register request Hi All, Can someone explain me the importance of CSeq in REGISTER request? RFC 3261 specifies that UA must increment the CSeq value by one for each REGISTER request with the same Call-ID. What is the expected response from a registrar if a UA keeps retransmitting the REGISTER request with same CSeq value and the same Call-ID? Thanks a lot, CoolGoose. _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors "DISCLAIMER: This message is proprietary to Aricent and is intended solely for the use of the individual to whom it is addressed. It may contain privileged or confidential information and should not be circulated or used for any purpose other than for what it is intended. If you have received this message in error,please notify the originator immediately. If you are not the intended recipient, you are notified that you are strictly prohibited from using, copying, altering, or disclosing the contents of this message. Aricent accepts no responsibility for loss or damage arising from the use of the information transmitted by this email including damage from virus." _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
