How it works
The calling endpoint sends an INVITE to the intended recipient, often including an SDP offer describing supported media. Provisional responses indicate call progress. A successful session is typically confirmed with 200 OK and ACK, while audio travels separately over the media path.
Business example
An agent selects a customer in a CRM and clicks Call. The softphone sends an INVITE through the PBX along the configured route.
What to consider
Inspect the full SIP exchange rather than the INVITE alone. A successfully established session does not guarantee good RTP quality or rule out one-way audio.