SIP
513 Message Too Large
The server was unable to process the request since the entire SIP message (not just the body) exceeded the size limit.
When You See This Code
When the total SIP message (headers + body) is too large. Different from 413 which refers only to the body.
How to Fix
Reduce the message size by removing unnecessary headers or reducing the SDP size. Consider using UDP-compatible message sizes (< 1300 bytes).