SIP 100 Trying vs 413 Request Entity Too Large
SIP 100 (Trying) is a 1xx Provisional response, while 413 (Request Entity Too Large) 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, 413 means that the server is refusing to process the request because the message body is larger than the server is willing to accept.
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 server is refusing to process the request because the message body is larger than the server is willing to accept.
When You See It
When sending a SIP message with a body (SDP, XML, etc.) that exceeds the server's size limit.
How to Fix
Reduce the size of the message body. For SDP, minimize codec offers or remove unnecessary attributes.
Key Differences
100 is a 1xx Provisional response, while 413 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 413: The server is refusing to process the request because the message body is larger than the server is willing to accept.
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 413 when when sending a SIP message with a body (SDP, XML, etc.) that exceeds the server's size limit.
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 413 (Request Entity Too Large): Reduce the size of the message body. For SDP, minimize codec offers or remove unnecessary attributes.