sip -->session inition protocol; 會議初始協議;
sdp --> session description protocol;會議描述協議;
nat -->network address translation; 網絡地址轉換;
rtp --> Real-time Transport protocol; 實時傳輸協議;
rtcp --> Real-time Transport Control Protocol; 實時傳輸控制協議;
uac --> user agent client; 用戶代理客戶端;
uas --> user agent server ; 用戶代理服務器端;