IMS: When the following response codes are used during an established IMS call session ?

Question

Redirection (3xx), Client failure (4xx), Server failure (5xx) and Global failure (6xx) in which scenarios these codes are used ?

Answer 1

Session Initiation Protocol (SIP) uses various response codes under the different categories/scenarios. I am going to explain almost all of those categories as following:
- Informational Response : When the request is accepted, server responds with 1xx. For example: 100 trying, 180 ringing.
- Successful Response: 200 OK or 202 accepted
- Redirection : When further action needs to be taken to complete the request. 301 moved permanently, 302 moved temporarily
- Client Failure : When server found the request received from client is not correct. 401 unauthorized and 403 forbidden
- Server Failure : When server failed to fulfill an apparently valid request. 500 server Internal Error and 504 server time out.
- Global Failure : The request can not be fulfilled at any server. 600 busy everywhere and 604 does not exist anywhere.

Hope it will help you up to some extent.