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1xx: Provisional Responses
- 100 Trying: The request has been received by the next hop and is being processed.
- 180 Ringing: The user agent has received an INVITE and is alerting the user.
- 181 Call Is Being Forwarded: The call is being forwarded to another endpoint.
- 182 Queued: Indicates that the call is queued.
- 183 Session Progress: Provides information about the progress of the call which is not necessarily an alert.
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2xx: Successful Responses
- 200 OK: The request was successful.
- 202 Accepted: Indicates that the request has been accepted for processing, but the processing is not complete.
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3xx: Redirection Responses
- 300 Multiple Choices: The address resolved to multiple choices, each with its own specific location.
- 301 Moved Permanently: The user can no longer be found at the address specified.
- 302 Moved Temporarily: The user is temporarily at a different location.
- 305 Use Proxy: The contact address must be contacted through a proxy.
- 380 Alternative Service: The call failed, but alternative services are available.
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4xx: Client Failure Responses
- 400 Bad Request: The request could not be understood due to malformed syntax.
- 401 Unauthorized: The request requires user authentication.
- 402 Payment Required: Reserved for future use.
- 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.
- 405 Method Not Allowed: The method specified in the request is not allowed.
- 406 Not Acceptable: The resource identified by the request is only capable of generating response entities that have content characteristics not acceptable according to the accept headers sent in the request.
- 407 Proxy Authentication Required: The client must first authenticate itself with the proxy.
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5xx: Server Failure Responses
- 500 Server Internal Error: The server encountered an unexpected condition.
- 501 Not Implemented: The server does not support the functionality required to fulfill the request.
- 502 Bad Gateway: The server received an invalid response from the upstream server.
- 503 Service Unavailable: The server is currently unable to handle the request.
- 504 Server Time-out: The server did not receive a timely response from an upstream server.
- 505 Version Not Supported: The SIP version in the request is not supported by the server.
- 513 Message Too Large: The message body is too large.
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6xx: Global Failure Responses
- 600 Busy Everywhere: All possible destinations are busy.
- 603 Decline: The destination does not wish to participate in the call.
- 604 Does Not Exist Anywhere: The server has authoritative information that the user does not exist anywhere.
- 606 Not Acceptable: The request was not acceptable due to the specified conditions.
Stay informed and keep your communications seamless!
