I’ve had several students ask me while lecturing on SIP response codes, “What is the difference between a SIP response ’603 Decline’ and a SIP response ’486 Busy Here’? When is it appropriate to send a 6xx response, and when is it appropriate to send a 4xx response?”
In short, all 6xx responses will terminate SIP dialog and any pending searches, whereas a 486 response would indicate that the user is not available at a particular request-URI.
I’ve constructed a video that demonstrates the difference between these two responses. It might even answer a few questions you didn’t even know you […]