*"Does the SIP UAS can init a TCP connection to the SIP UAC if the UAC is behind the NAT?*"
Not too sure. SIP/RTP with NAT usually is a source of quite a few problems so many avoid it. Investigate STUN or ICE, as they try to solve some of these problems. RTP over NAT usually causes a headache because ports are usually chosen on the fly for audio routing. e.g. during SDP Offer/Answer, a UAC might choose some high numbered port such as 50505. Since the UAC is behind NAT, it can listen all it wants on 50505, but since it's behind NAT, the UAS would not be able to send RTP to the UAC. One solution is to avoid NAT altogether and place the UAC in a DMZ (Demilitarized Zone). Then you wouldn't have to mess with port forwarding. *"And Does the SIP UAS needs keep the TCP connection alive all the time with the UAC?"* * * If the UAC (behind NAT) initiated the TCP connection to the UAS (public network), the TCP protocol should handle keeping the connection alive, and NAT would be informed during keep alive messages to "keep the pathway open". On Thu, Sep 26, 2013 at 11:39 AM, Guan Xsun <[email protected]> wrote: > Hi, > Does the SIP UAS can init a TCP connection to the SIP UAC if the UAC > is behind the NAT? > And Does the SIP UAS needs keep the TCP connection alive all the time > with the UAC? > > Thanks > Casey > > > 2013/9/24 Thomas Buono <[email protected]> > >> Guan, >> >> SIP is an application layer protocol, so most of the dialog creation and >> registration is done independent of the transport layer protocol. RFC 3261 >> provides most if not all of the information you are looking for. >> >> See the "transport=tcp" parameter. >> >> >> >> >> On Tue, Sep 24, 2013 at 6:04 AM, Guan Xsun <[email protected]> wrote: >> >>> Hi, >>> I am developing a SIP server over TCP. >>> Could you tell me which RFC doc describes how SIP servers use TCP to >>> transmit SIP message, create SIP dialog and Register? >>> >>> Best Regards! >>> Casey >>> _______________________________________________ >>> Sip-implementors mailing list >>> [email protected] >>> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors >>> >> >> > _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
