100

Trying

Extended search is being performed so a forking proxy must send a 100 Trying response.

180

Ringing

The Destination User Agent has received the INVITE message and is alerting the user of call.

181

Call Is Being Forwarded

Optional, send by Server to indicate a call is being forwarded.

182

Queued

Destination was temporarily unavailable, the server has queued the call until the destination is available.

183

Session Progress

This response may be used to send extra information for a call which is still being set up.

199

Early Dialog Terminated

Sent by the User Agent Server to indicate that an early dialogue has been terminated.

200

OK

Shows that the request was successful.

202

Accepted

Indicates that the request has been accepted for processing, mainly used for referrals.

204

No notification

Indicates that the request was successful but no response will be received.

300

Multiple choices

The address resolved to one of several options for the user or client to choose between.

301

Moved permanently

The original Request URI is no longer valid, the new address is given in the Contact header.

302

Moved temporarily

The client should try at the address in the Contact field.

305

Use proxy

The Contact field details a proxy that must be used to access the requested destination.

380

Alternative service

The call failed, but alternatives are detailed in the message body.

400

Bad Request

The request could not be understood due to malformed syntax.

401

Unauthorized

The request requires user authentication. This response is issued by a UAS or a registrar.

403

Forbidden

The server understood the request, but is refusing to fulfill it.

404

Not found

The server has definitive information that the user does not exist at the (User not found)

407

Proxy authentication required

The request requires user authentication.

408

Request timeout

Couldn’t find the user in time.

409

Conflict

User already registered (deprecated).

411

Length required

The server will not accept the request without a valid content length (deprecated).

412

Conditional request failed

The given precondition has not been met.

415

Unsupported media type

Request body is in a non-supported format.

424

Bad location information

The request’s location content was malformed or otherwise unsatisfactory.

436

Identity info

The request has an Identity-Info header and the   URI scheme contained cannot be de-referenced.

407

Consent needed

The source of the request did not have the permission of the recipient to make such a request.

480

Temporarily unavailable

Callee currently unavailable.

481

Call/Transaction does not exist

Server received a request that does not match any dialogue or transaction.

484

Address incomplete

Request-URI incomplete.

486

Busy here

Callee is busy.

488

Not acceptable here

Some aspects of the session description of the Request-URI are not acceptable.

489

Bad event

The server did not understand an event package specified in an Event header field.

500

Server internal error

The server could not fulfill the request due to some unexpected condition.

501

Not implemented

The SIP request method is not implemented here.

502

Bad gateway

The server, received an invalid response from a downstream server while trying to fulfill a request.

503

Service unavailable

The server is in maintenance or is temporarily overloaded and cannot process the request.

504

Server time-out

The server tried to access another server while trying to process a request, no timely response.

505

Version not supported

The SIP protocol version in the request is not supported by the server.

513

Message too large

The request message length is longer than the server can process.

555

Push notification service not supported

The server does not support the push notification service specified in the pn-provider SIP URI parameter.

580

Precondition failure

The server is unable or unwilling to meet some constraints specified in the offer.

600

Busy everywhere

All possible destinations are busy.

603

Decline

Destination cannot/doesn’t wish to participate in the call,  no alternative destinations.

604

Does not exist anywhere

The server has authoritative information that the requested user does not exist anywhere.

606

Not acceptable

The server has authoritative information that the requested user does not exist anywhere.

607

Unwanted

The called party did not want his call from the calling party. Future attempts from the calling party are likely to be similarly rejected.

608

Rejected

An intermediary machine or process rejected the call attempt.