Common SIP Response Codes

100 Trying: Caller is attempting to make the call.

180 Ringing: Call is progressing.

183 Progressing: Call is progressing. Ringing is normally heard.

200 OK: Successful request. During a call invite, this means the start of the call.

302 Temporarily Moved: A new address will be given in the contact header field, which can be retried by the requesting client.

404 Not Found: Request URI isn’t found. This could be a bad number or extension.

407 Proxy Auth Required: Invite received but was missing the authentication. This is expected. The remote party should respond back with authentication.

486 Busy Here: The called party is busy.

503 Service Unavailable: The system is undergoing maintenance or is temporarily overloaded. The expected behavior is to move to the next resource. Different endpoints and firmware will respond differently. This is sometimes configurable.

606 Not Acceptable: Some aspects of the session description are not acceptable. This could be requested media, bandwidth, or addressing style.

About The Author:

Cody Deluisio is a dedicated network engineer specializing in hotel PBX systems and network solutions, with expertise in UniFi, Aruba, Ruckus, and a variety of other technologies. Outside of his tech career, Cody runs an organic farm in Bell Township, PA, where he focuses on sustainable and regenerative farming practices. Balancing the fast-paced world of networking with the tranquility of farm life, Cody brings a unique perspective to both his professional and personal endeavors.