overview of user terminal interfaces edoardo berera university of nice sophia antipolis telelinea 26...

Overview of User Terminal Interfaces

Edoardo BereraUniversity of Nice Sophia Antipolis

Telelinea

26 September 2001

Seminar on Electronic Commerce24-28 September 2001

E. Berera UNSA / Telelinea 2

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


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,…?


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


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 ?


Basic Service

• Local and long-distance calls• Usage

– Voice – Fax– Internet access

• Tariffs– Duration– Distance

• Circuit Switched Network

01 23 45 67 89

01 23 45 67 89


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

04 12 34 56 78


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


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

SSP Intelligent PeripheralModem/Fax

Answering machine


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


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


Integrated IP Telephony Example

• Distance education• Tutor works on a computer

at the university connected to the Internet

applicationpresentation

sessiontransportnetwork

physical

OSI stack Internet stack

HTTP, SMTP

TCP,UDP

IPv4, IPv6

IEEE802.xdata link


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.323 RTSP SIP RTCP RSVP

TCP UDP

SDP Media

RTP


Signaling Protocols

• User Location– Where is the callee ? Which (dynamic) IP address ?

• Session Establishment– Accept, reject, redirect (voicemail, web page)

• Session Negotiation– Multimedia session, capabilities exchange

• Call Participation Mgmt– Add new participants; participants may leave session

• Feature Invocation– Hold, transfer, mute, ...


SIP Operation

• Example– sip:[email protected]

• 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


SIP Message Structure

• sip:[email protected]• Signaling message

INVITE– similar to e-mail

• Message content (payload)– Session Description (SDP)

• c: caller’s address• m: media• a: attribute

– May contain more info

© GMD FOKUS, SIP Tutorial, 2001


SIP Methods

• INVITE– initiates sessions– session description included in message body

• ACK– confirms session establishment

• BYE– terminates sessions

• CANCEL– cancels a pending INVITE


SIP Methods (cont.)

• OPTIONS– capability inquiry

• REGISTER– binds a permanent address to current location– may convey user data (CPL scripts)


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


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 e-mail• send an instant message

© IEEE Network, Henning Schulzrinne, Jonathan Lennox, Columbia University, Jonathan Rosenberg, Bell Labs-Lucent Technologies, May/June 1999

CPL Example

<call>  <location url="sip:[email protected]"> <proxy timeout="8s">

 <busy> <location url="sip:[email protected]" merge="clear" id="voicemail" > <proxy /> </location> </busy>

 <noanswer> <link ref="voicemail" /> </noanswer> </proxy> </location> </call>

© IEEE Network, Henning Schulzrinne, Jonathan Lennox, Columbia University, Jonathan Rosenberg, Bell Labs-Lucent Technologies, May/June 1999


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

– sip:[email protected]

• at the university– sip:[email protected]

• on her cellular phone– sip:[email protected]

Home PC

University Workstation

Clara ?

M

Source: Mampaey, Alcatel (© IEEE Communications, Oct. 2000, p. 105)


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


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.323 RTSP SIP RTCP RSVP

TCP UDP

SDP

RTP

Clara will receive the audio and only text… for the moment !


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


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


Online Resources

• IEEE– http://computer.org/internet/telephony

• GMD Fokus– http://www.fokus.gmd.de/glone/projects/ipt/

• Columbia University– http://www.cs.columbia.edu/~hgs/sip

• Free World Dialup– http://www.pulver.com

overview of user terminal interfaces edoardo berera university of nice sophia antipolis telelinea 26...

Documents

voice transport network

network ss7

ss7 slide

network servers packet

machine slide

modem slide

exhaustive slide

tools slide