Hi, We are testing the REGISTRAR with kamailio. We tested the following scenario , è Register Request with contact ‘A’. è 200 OK received for the request è Second Register request with contact ‘B’. (Requet-URI, To Tag, From tag, call-id, and Cseq -> all same as the first register request) è 200 OK received for the request. When we checked the ‘location’ table entry, two records were found for the same user with different contact addresses. Please find below the RFC extract below, Section 17.2.3 For all other request methods, a request is matched to a transaction if the Request-URI, To tag, From tag, Call-ID, CSeq (including the method), and top Via header field match those of the request that created the transaction. Matching is done based on the matching rules defined for each of those header fields. When a non-INVITE request matches an existing transaction, it is a retransmission of the request that created that transaction. My understanding is that the second register request should be considered as duplicate and rejected. Please share your feedback on the same. Regards, Shankar