SIP 100 Trying vs 400 Bad Request
SIP 100 (Trying) is a 1xx Provisional response, while 400 (Bad Request) is a 4xx Client Failure response. 100 indicates that the request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses. In contrast, 400 means that the request could not be understood due to malformed syntax. The client should not repeat the request without modifications.
描述
The request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses.
何时出现
Immediately after sending an INVITE. The proxy has received the call and is searching for the callee. This is the SIP equivalent of a dial tone.
如何修复
No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration.
描述
The request could not be understood due to malformed syntax. The client should not repeat the request without modifications.
何时出现
When the SIP message has syntax errors, missing required headers, or invalid header values.
如何修复
Review the SIP message for syntax errors. Check required headers (To, From, Call-ID, CSeq, Via, Max-Forwards) and ensure proper formatting.
主要区别
100 is a 1xx Provisional response, while 400 is a 4xx Client Failure response.
SIP 100: The request has been received by the next-hop server and an unspecified action is being taken to process it. The UAC should expect additional responses.
SIP 400: The request could not be understood due to malformed syntax. The client should not repeat the request without modifications.
You encounter 100 when immediately after sending an INVITE. The proxy has received the call and is searching for the callee. This is the SIP equivalent of a dial tone.
You encounter 400 when when the SIP message has syntax errors, missing required headers, or invalid header values.
何时使用哪个
For 100 (Trying): No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration. For 400 (Bad Request): Review the SIP message for syntax errors. Check required headers (To, From, Call-ID, CSeq, Via, Max-Forwards) and ensure proper formatting.