SIP – Application layer protocol SIP Requests SIP responses Session Description Protocol  (SDP) SIP transactions, dialog , branch Matching in-dialog transactions/requests Record Routing strict routing loose routing Mobility and Location Service Network Address Translator ( NAT) Far End Traversal Near End Traversal SIP Call Flows Registeration Call Redirection Forking click to Dial SIP for Instant … Continue reading SIP ( Session Initiation Protocol )