VoIP & telephony
Every SIP response code from 100 Trying to 608 Rejected: what each one means, why it happens and what to check, with the matching Q.850 causes.
The request is being processed; more responses will follow.
The request succeeded.
The request should be sent elsewhere; the new address is in the Contact header.
The request has a problem on the sender’s side or cannot be completed at this server. Retrying the same request will not help.
The server failed to handle a valid request. Another server or a later attempt may succeed.
The call cannot succeed anywhere: do not try other locations.
Nothing found.
The first digit is the class. 1xx are interim responses (the call is progressing), 2xx success, 3xx redirection, 4xx a problem with the request or the callee, 5xx a server failure, 6xx a global failure. The text after the number varies between vendors; go by the number.