Transcript Lecture 2
RTMMoIP Alfredo Terzoli / Mosioua Tsietsi PLAN • Did you read the hand-out? • A few important acronyms • A call is more than a conversation: signalling! • Timeline & general organization A few acronyms for you to expand • • • • • • PBX TDM PSTN T1 SS7 SIP Solutions • • • • PBX : Private Branch Exchange TDM : Time Division Multiplexing PSTN : Public Switched Telephone Network T1 : Trunk (level) 1 (ok, a bit strange); btw, in SA is normally E1 – 2 Mbps • SS7 : Signalling System 7 • SIP : Session Initiation Protocol Legacy service provider use TDM network 1 SER GnuG K Asteris k iLanga proxy iLanga Core TDM network 2 SER IP Network (Typically not the Internet) GnuG K Asteris k iLanga proxy iLanga Core Enterprise setting Local VoIP Endpoints SIP IAX H.323 MGCP Internet SER GnuGK Asterisk iLanga proxy Legacy PBX BRI PRI iLanga Core PSTN BRI PRI VoIP signalling protocols • SIP: Session Initiation Protocol – IETF, Internet Engineering Task Force • H.323 – ITU, International Telecommunication Union • MGCP: Media Gateway Control Protocol - ITU • H.248/MEGACO: MEdia GAteway COntrol – ITU / IETF SIP • In a sense the child of SMTP (Simple Mail Transport Protocol) and HTTP (Hyper Text Transfer Protocol) • Simple: – establishes the session only – uses SDP, for the description of the session – RTP for the transport of the media User Agent UAS – server UAS – server UAC – client UAC – client A simple SIP network A SIP conversation Some experiments • First, let’s get ourselves a SIP UA besides the one embedded in the telephone: – SJphone, www.sjlabs.com (& in the software resources for this module) Experiments • Experiment 1: let’s call directly the hardphone, using its IP address • Experiment 2: let’s call the hardphone via iLanga, but without being part of iLanga (btw, this is the way the rest of the world can contact you) • Experiment 3: let’s join iLanga and start using the extensions and dialling out to the PSTN Got a packet sniffer? • A good idea not to get bored with networks is to use a packet analyzer • If you don’t have one already, use WireShark, http://www.wireshark.org or in the software resources of this module The INVITE message Rough timeline • First week: general VoIP concepts + SIP – your work: reading, playing with SIP UA, analyzing SIP and RTP packets • Second week: more SIP + Asterisk – your work: reading, experimenting with Asterisk; thinking about a service you want to create • Third week: more Asterisk, presentation of your service idea – your work: reading, starting putting together your service, Questions?