Voice over IP or Session Initiation Protocol (SIP) is a signaling communications protocol,
widely used for controlling multimedia communication sessions such as voice and video
calls over IP networks.
Agile CRM integrates with VoIP (SIP) providers to offer a complete CRM telephony suite
to its customers. No downloads, no installations, only a one-time integration with the SIP
widget to start calling your customers right from the CRM.
Here's a detailed setup description of the Agile's VoIP integration