SIP Registration Behavior

I am registering to a SIP server (Asterisk) using X-lite softphone. According to the SIP RFC, for registration process the softphone should send a REGISTER request and receive 401 response with nonce value, again it should send a REGISTER request with credentials and should receive 200 OK response indicating successful registration.

I am observing a different behavior while registering to the SIP server. The softphone is registering with 2 REGISTER requests and receive 2 responses (first 401 and then 200). After successful registration it is sending 2 Register requests with responses 401 and 200 respectively to de-register the softphone and at the end it has re-registered with 2 REGISTER requests and 2 responses. Could you please elaborate why I have extra registration and de-registration?

thanks in advance.

That’d be the client doing that, why… we wouldn’t really know. If you provide the actual log of it happening it may provide some insight, otherwise looking at logs for the client might tell you why.

For reference I am sending you the screenshot of the pcap file I have. It is not allowed to upload pcap file here. Maybe if you provide me your email I can send you the pcap file for better understanding.