Overview of User Terminal Interfaces Edoardo Berera University of Nice Sophia Antipolis Telelinea 26 September 2001 Seminar on Electronic Commerce September 2001

E. BereraUNSA / Telelinea2 Objectives A common understanding of –Variety of user terminals –Underlying networks and their interconnections –Servers and protocols Non goals –To describe any specific e-commerce application –To be exhaustive

E. BereraUNSA / Telelinea3 Which “things” do we use to communicate ? Terminals –Telephones, PCs –but also …? Networks –Phone net, Internet –but also … ? Languages, protocols –English, HTML, SMS… ? –HTTP, WAP, … ? Servers –Yellow Pages, Yahoo,…?

E. BereraUNSA / Telelinea4 Information Utility Information system developers must –understand how to interconnect all the components terminals, switches, routers, gateways, satellites, servers –using a variety of languages, programs, protocols and tools

E. BereraUNSA / Telelinea5 Keep it simple please: Tin Can Telephones Did you ever build tin can telephones when you were children ? Simple device that allows you to talk at one end and get someone to listen at some distance at the other end Can you analyze this communication system ?

E. BereraUNSA / Telelinea6 Basic Service Local and long-distance calls Usage –Voice –Fax –Internet access Tariffs –Duration –Distance Circuit Switched Network

E. BereraUNSA / Telelinea7 112 Intelligent Services Emergency calls –112 in Europe –911 in USA Where is the number translation done ? Where is the “intelligence” ? –“800” numbers –Services Toll free (callee pays !) Special rates Location / time dependent

E. BereraUNSA / Telelinea8 Intelligent Network (IN) Network servers provide service intelligence (e.g. number translations) Separation between –Voice transport network Circuit switched network –Signaling network (call control) Packet switched network SS7 Signaling System n°7 112 SS7

E. BereraUNSA / Telelinea9 IN Components Service Control Point (SCP) Signaling Transfer Point (STP) Service Switching Point (SSP) usually integrated in the telephone switches Intelligent Peripherals –Interactive Voice Response (IVR) –Media Gateways SCP STP SSPIntelligent PeripheralModem/Fax Answering machine

E. BereraUNSA / Telelinea10 Modern Telephone Network Structure Dumb terminals (little or no intelligence in normal telephones) Advanced services provided by network servers Packet switched signaling network (call control messages) Circuit switched voice transport network

E. BereraUNSA / Telelinea11 Internet and the Intelligent Network Internet structure: –Application servers –Network routers –Intelligent terminals Workstations, PC, PDA IN programmable components –Service Control Points –Intelligent Peripherals –Dumb (?) terminals Phone PC and a modem

E. BereraUNSA / Telelinea12 Integrated IP Telephony Example Distance education Tutor works on a computer at the university connected to the Internet application presentation session transport network physical OSI stackInternet stack HTTP, SMTP TCP,UDP IPv4, IPv6 IEEE802.x data link

E. BereraUNSA / Telelinea13 IP Telephony Protocols Tutor receives an audio and video call from Bruno SIP –Session Initiation Protocol SDP –Session Description Prot. RTP –Real-time Transport Prot. IPv4, IPv6 H.323RTSPSIPRTCPRSVP TCPUDP SDP Media RTP

E. BereraUNSA / Telelinea14 Signaling Protocols User Location –Where is the callee ? Which (dynamic) IP address ? Session Establishment –Accept, reject, redirect (voic , web page) Session Negotiation –Multimedia session, capabilities exchange Call Participation Mgmt –Add new participants; participants may leave session Feature Invocation –Hold, transfer, mute,...

E. BereraUNSA / Telelinea15 SIP Operation Example SIP User Agent Client SIP Proxy Server SIP Redirect Server SIP Registration Server SIP User Agent Server © IEEE Network, Henning Schulzrinne, Columbia University, Jonathan Rosenberg, Bell Labs-Lucent Technologies, May/June 1999

E. BereraUNSA / Telelinea16 SIP Message Structure Signaling message INVITE –similar to Message content (payload) –Session Description (SDP) c: caller’s address m: media a: attribute –May contain more info © GMD FOKUS, SIP Tutorial, 2001

E. BereraUNSA / Telelinea17 SIP Methods INVITE –initiates sessions –session description included in message body ACK –confirms session establishment BYE –terminates sessions CANCEL –cancels a pending INVITE

E. BereraUNSA / Telelinea18 SIP Methods (cont.) OPTIONS –capability inquiry REGISTER –binds a permanent address to current location –may convey user data (CPL scripts)

E. BereraUNSA / Telelinea19 Model for Programming SIP SIP server augmented with service logic (programs) –SIP Common Gateway Interface (CGI) flexible for trusted users operators, administrators –similar to HTTP CGI –Call Processing Language (CPL) simpler, more restricted for untrusted users consumers –based on XML © IEEE Network, Henning Schulzrinne, Jonathan Lennox, Columbia University, Jonathan Rosenberg, Bell Labs-Lucent Technologies, May/June 1999

E. BereraUNSA / Telelinea20 Example CPL Decision Graph Directed acyclic graph –Decision (switch) nodes –Location nodes –Signaling actions nodes proxy redirect response –Non-signaling actions nodes log send an send an instant message © IEEE Network, Henning Schulzrinne, Jonathan Lennox, Columbia University, Jonathan Rosenberg, Bell Labs-Lucent Technologies, May/June 1999

E. BereraUNSA / Telelinea21 CPL Example © IEEE Network, Henning Schulzrinne, Jonathan Lennox, Columbia University, Jonathan Rosenberg, Bell Labs-Lucent Technologies, May/June 1999

E. BereraUNSA / Telelinea22 IP Telephony and Agent Software Tutor and Bruno need to talk to Clara Clara works at home and at the university –Personal agent software will ring Clara at home at the university on her cellular phone Home PC University Workstation Clara ? M Source: Mampaey, Alcatel (© IEEE Communications, Oct. 2000, p. 105)

E. BereraUNSA / Telelinea23 Cellular Telephony Clara in on the train she answers the call –WAP enabled GSM cellular phone How did the cellular network find Clara ? –In which cell is she actually in ? And the train is moving fast –TGV, ICE, Pendolino –cell handover problem redirection

E. BereraUNSA / Telelinea24 Global System for Mobile (GSM) Source: Oliphant, IFR (© IEEE Spectrum, Aug. 1999, p. 21)

E. BereraUNSA / Telelinea25 Streaming Media –Tutor recalls a tutorial stored on the university video server and decides to play it –Bruno receives both audio and video Media IPv4, IPv6 H.323RTSPSIPRTCPRSVP TCPUDP SDP RTP Clara will receive the audio and only text… for the moment !

E. BereraUNSA / Telelinea26 References Henning Schulzrinne, Columbia University, Jonathan Rosenberg, Bell Laboratories-Lucent Technologies, “The IETF Internet Telephony Architecture and Protocols”, IEEE Internet Computing, May/June 1999 Jonathan Rosenberg, Bell Laboratories, Jonathan Lennox, Henning Schulzrinne, Columbia University, “Programming Internet Telephony Services”, IEEE Internet Computing, May/June 1999 Dorgham Sisalem, Jiri Kuthan, Mobile Integrated Services, GMD Fokus, “Understanding SIP”, 2001

E. BereraUNSA / Telelinea27 RFCs and Internet Drafts SIP: RFC 2543 SDP: RFC 2327 SIP call flows: draft-ietf-sip-call-flows SIP services call flows: draft-ietf-sip-service- examples SIP-CGI: RFC 3050 CPL: draft-iptel-cpl

E. BereraUNSA / Telelinea28 Online Resources IEEE – GMD Fokus – Columbia University – Free World Dialup –