Answers in this category: What is the relationship between MGCP and SIP? What is SIP+ and how does it relate to SIP How does SIP compare to H.323? Can H.323 and SIP be used together? How do I interconnect Q.931 (ISDN signaling) and SIP? How do I interconnect ISUP (SS7 signaling) and SIP? Where do I find description of SDP? Can SIP be used for Internet telephony gateways (ITGs)? What is sip-cgi and how does it relate to CPL? Is there a SIP interoperability certification? How can I test interoperability with others? Why use SIP-T as opposed to tunneling SS7 using SCTP? How does SIP carry DTMF (touch tones)? What is the relationship of a "softswitch" to SIP? How does SIP/SDP relate to T.38 fax calls? Where is the use of SIP defined in 3GPP? What port numbers should I use for RTP sessions set up with SIP? Why use SIP for presence and instant messaging?