SIP 100 Trying vs 305 Use Proxy
SIP 100 (Trying) is a 1xx Provisional response, while 305 (Use Proxy) is a 3xx Redirection 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, 305 means that the requested resource must be accessed through the proxy given by the Contact header field.
Description
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.
When You See It
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.
How to Fix
No fix needed — this is normal call setup behavior. If stuck on 100 Trying for too long, check network connectivity and proxy configuration.
Description
The requested resource must be accessed through the proxy given by the Contact header field.
When You See It
When the request must be routed through a specific outbound proxy server.
How to Fix
Resend the request through the proxy specified in the Contact header of this response.
Key Differences
100 is a 1xx Provisional response, while 305 is a 3xx Redirection 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 305: The requested resource must be accessed through the proxy given by the Contact header field.
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 305 when when the request must be routed through a specific outbound proxy server.
When to Use Which
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 305 (Use Proxy): Resend the request through the proxy specified in the Contact header of this response.