early media

early_media_handle/README.md

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+# Early Media Handling 
+
+## RFC on early media 
+
+Early Media is the ability of two SIP user agents to communicate before a SIP call is actually established.
+Common cases where called party is PSTN gateway and plays inband tones or announcements before the call is set up , mostly to share call progress information with caller.
+Can also be used in IVR cases when caller needs to enter DTMF digit in order to connect to final destination after dialing a toll free ( 80's ) number 
+
+Early media usually comes aling with 183 Ringing and not 200 , since a 2xx class response to an INVITE both establishes a media session, and indicates acceptance of the call , where as early media only estalishes media not answer the call
+
+Ref :
+
+https://tools.ietf.org/html/draft-rosenberg-sip-early-media-00