SIP 100 Trying vs 202 Accepted
SIP 100 (Trying) is a 1xx Provisional response, while 202 (Accepted) is a 2xx Success 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, 202 means that the request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
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 request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
When You See It
After sending a REFER request for call transfer. The transfer target acknowledges receipt but hasn't completed the transfer yet.
How to Fix
Wait for a NOTIFY to learn the outcome of the referred action. If no NOTIFY arrives, check subscription state and network connectivity.
Key Differences
100 is a 1xx Provisional response, while 202 is a 2xx Success 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 202: The request has been accepted for processing but the processing has not been completed. Used primarily for REFER requests.
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 202 when after sending a REFER request for call transfer. The transfer target acknowledges receipt but hasn't completed the transfer yet.
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 202 (Accepted): Wait for a NOTIFY to learn the outcome of the referred action. If no NOTIFY arrives, check subscription state and network connectivity.