Code

Event name

Reason

400

Bad request

The request couldn't be processed due to syntax error.

401

Unauthorized

The request that was received requires user authentication. Usually the client will ask the user for it.

402

Payment required

This is reserved for future use.

403

Forbidden

The server has understood the request, but is refusing to perform it. The client should not try it again.

404

Not found

The server notifies the client that the user does not exist in the domain specified in the Request URI.

405

Method not allowed

A method sent by the client is not allowed to be used by it. The response will include an allow header field to notify the sender which methods he is allowed to use.

406

Not acceptable

The resource identified by the request is only capable of generating response entities that have unacceptable content characteristics according to the accept header field sent in the request.

407

Proxy authentication required

The client must authenticate with a proxy server.

408

Request timeout

The server couldn't respond during the expected time. The client may send the request again after a while.

410

Gone

The requested resource is no longer available at the server, and the forwarding address is not known. This condition is considered to be permanent.

413

Request entity too large

The server is refusing to process a request because the request entity's body is larger than what the server is able or willing to process.

414

Request-URI too long

The server is refusing to service the request because the Request URI is longer than what the server is able or willing to interpret.

415

Unsupported media type

The server is refusing to process the request because the message body of the request is in a format that is not supported by the server.

416

Unsupported URI scheme

Request URI is unknown to the server, and therefore, the server cannot process the request.

420

Bad extension

The server did not understand the protocol extension received from the client.

421

Extension required

The UA that received the request requires a particular extension in order to process it, but this extension is not listed in the supported header field of the request.

423

Interval too brief

The server is rejecting the request because the expiration time of the resource refreshed by the request is too short.

424

Bad location information

This response code indicates a rejection of the request due to its location contents. This indicates malformed or unsatisfactory location information (RFC6442).

428

Use Identity header

It is sent when a verifier receives an SIP request that lacks an Identity header in order to indicate that the request should be re-sent with an Identity header (RFC4474).

429

Provide referrer identity

This provides referrer identity (RFC3892).

433

Anonymity disallowed

This indicates that the server refused to satisfy the request because the requestor was anonymous (RFC5079).

436

Bad identity info

This response is used when there is bad information in the Identity-Info header (RFC4474).

437

Unsupported certificate

This is used when the verifier cannot validate the certificate referenced by the URI in the Identity-Info header (RFC4474).

438

Invalid identity header

This is used when the verifier (the receiver UA) receives a message with an Identity signature that does not correspond to the digest-string calculated by the verifier (RFC4474).

470

Consent needed

This is the response to a request that contained a URI list in which at least one URI was such that the relay had no access permissions (RFC5360).

480

Temporarily unavailable

The caller's end system was contacted successfully, but the caller is currently unavailable.

481

Call/transaction does not exist

The receiving UA received a request that does not match any existing transaction or dialog.

482

Loop detected

The server has detected a loop.

483

Too many hops

The server received a request that contains a Max-Forwards header field that equals zero.

484

Address incomplete

The server received a request with an incomplete Request-URI.

485

Ambiguous

The Request-URI was unclear. The response may contain a listing of possible addresses in the Contact header fields.

486

Busy here

The caller's end system was contacted successfully, but the caller is currently unable or unwilling to take additional calls by this end system.

487

Request terminated

The request was terminated by a BYE or CANCEL request.

488

Not acceptable here

Specific resources addressed by the Request-URI are not accepted.

491

Request pending

The receiving UA had a pending request.

493

Undecipherable

The request contains an encrypted MIME body, which cannot be decrypted by the recipient.