Early Media

Early media is the ability of two SIP User Agents to communicate before a SIP call is actually established. Typically, this scenario occurs when the called party is a PSTN gateway. Before the call is set up, the gateway might provide in-band tones or announcements that inform the caller of the call progress.

Early media can involve the transfer of media from caller to callee. Within the PSTN, forward channels can be established to convey DTMF signaling to select a final destination to call. This feature can be used to access Interactive Voice Response (IVR) systems “behind” 800 numbers.