IP Office SIP Trunk Define Outbound Caller ID establishes the core entities involved in phone calls: IP Office SIP Trunk, Outbound Caller ID, and IP Office. The IP Office SIP Trunk acts as a gateway to external calls, connecting to the PSTN. Outbound Caller ID controls the identity displayed to recipients. IP Office, the central hub, integrates these entities, managing call routing and handling features. Closeness values prioritize entities, ensuring optimal call flow.