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 | SIP Release Notes | 
 | 2. Supported Features | 
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 | 4xx Response | Supported | Comments | 
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 | 420 | 
 | Bad Extension | Yes | The device doesn't generate this response. Upon receipt of | 
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 | this message and before a 200 OK has been received, the | 
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 | device responds with an ACK and disconnects the call. | 
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 | 423 | 
 | Interval Too | Yes | The device does not generate this response. On reception | 
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 | Brief | 
 | of this message the device uses the value received in the | 
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 | 433 | 
 | Anonymity | Yes | If the device receives a 433 Anonymity Disallowed, it sends | 
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 | Disallowed | 
 | a DISCONNECT message to the PSTN with a cause value | 
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 | of 21 (Call Rejected). In addition, the device can be | 
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 | configured, using the Release Reason Mapping, to generate | 
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 | a 433 response when any cause is received from the PSTN | 
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 | 480 | 
 | Temporarily | Yes | If the device receives a 480 Temporarily Unavailable | 
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 | Unavailable | 
 | response, it notifies the User with a Reorder Tone. | 
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 | This response is issued if there is no response from remote. | 
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 | 481 | 
 | Call | Yes | The device doesn't generate this response. Upon receipt of | 
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 | Leg/Transaction | 
 | this message and before a 200 OK has been received, the | 
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 | Does Not Exist | 
 | device responds with an ACK and disconnects the call. | 
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 | 482 | 
 | Loop Detected | Yes | The device doesn't generate this response. Upon receipt of | 
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 | this message and before a 200 OK has been received, the | 
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 | device responds with an ACK and disconnects the call. | 
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 | 483 | 
 | Too Many Hops | Yes | The device doesn't generate this response. Upon receipt of | 
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 | this message and before a 200 OK has been received, the | 
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 | device responds with an ACK and disconnects the call. | 
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 | 484 | 
 | Address | Yes | The device doesn't generate this response. Upon receipt of | 
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 | Incomplete | 
 | this message and before a 200 OK has been received, the | 
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 | device responds with an ACK and disconnects the call. | 
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 | 485 | 
 | Ambiguous | Yes | The device doesn't generate this response. Upon receipt of | 
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 | this message and before a 200 OK has been received, the | 
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 | device responds with an ACK and disconnects the call. | 
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 | 486 | 
 | Busy Here | Yes | The SIP device generates this response if the called party is | 
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 | call. Upon receipt of this response, the device notifies the | 
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 | User and generates a busy tone. | 
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 | 487 | 
 | Request | Yes | This response indicates that the initial request is terminated | 
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 | Canceled | 
 | with a BYE or CANCEL request. | 
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 | 488 | 
 | Not Acceptable | Yes | The device doesn't generate this response. Upon receipt of | 
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 | this message and before a 200 OK has been received, the | 
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 | device responds with an ACK and disconnects the call. | 
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 | 491 | 
 | Request | Yes | When acting as a UAS: the device sent a  | 
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 | Pending | 
 | established session and is still in progress. If it receives a | 
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 | the received INVITE. | 
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 | When acting as a UAC: If the device receives a 491 | 
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 | response to a  | 
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 | expires, the UAC tries to send the  | 
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| Version 6.2 | 125 | December 2010 | 
