SIP trace

A SIP trace is a recording of the signaling messages that two systems exchange to set up, manage, and end a call. SIP stands for Session Initiation Protocol, the language phones and carriers use to say things like ringing, answered, busy, and hung up. A trace captures those messages in order so you can read the conversation between your dialer and the other side step by step.

Traces are the first thing you reach for when calls misbehave and nobody can explain why. Instead of guessing, you look at the actual exchange: did the SIP (Session Initiation Protocol) INVITE go out, did the Carrier reply, and what did it say. The reply carries a SIP response code — a number that tells you whether the call succeeded, was rejected, or hit a server problem like a SIP 503 Service Unavailable. Reading that number turns a vague complaint into a specific cause.

A trace shows both the signaling and clues about the media path. If calls connect but you get One-way audio, the signaling may look perfect while the audio negotiation reveals the real trouble. Pairing a SIP trace with the reason the call ended, the Hangup cause, usually pinpoints whether the fault is on your box, the carrier, or somewhere in between.

You capture traces with tools that watch the SIP traffic on your server. When you open a ticket with a carrier, a clean trace of a failing call is the most useful thing you can attach, because it removes argument about whose side broke. Save the trace, note the time and the numbers involved, and you will resolve carrier problems far faster than describing symptoms in words.