09-07-K.Steenhaut & J.Tiberghien - VUB 1 Telecommunications Concepts Chapter 1.1 Evolution of Telecommunications

09-07-K.Steenhaut & J.Tiberghien - VUB 2 Contents The 19th century telecommunications –Telegraph - Telephone –Digital vs. analog communications The voice networks & the data networks The electronics revolution ( ) –Digital sound –Mainframe computers with remote access –The first unification : ISDN –Local area networks –Wide area and local area networks integration The Internet –The research project –The universal computer communications medium –The successful unification ?

09-07-K.Steenhaut & J.Tiberghien - VUB 3 Contents The 19th century telecommunications –Telegraph - Telephone –Digital vs. analog communications The voice networks & the data networks The electronics revolution ( ) –Digital sound –Mainframe computers with remote access –The first unification : ISDN –Local area networks –Wide area and local area networks integration The Internet –The research project –The universal computer communications medium –The successful unification ?

09-07-K.Steenhaut & J.Tiberghien - VUB 4 The Chappe Telegraph (Claude Chappe, ) 92 out of 256 (= 4*8*8) positions represented characters. Integrity of message could be restored at each relay station In 1844, 534 relays linked Paris with 29 cities, covering in total 5000 Km.

09-07-K.Steenhaut & J.Tiberghien - VUB 5 The Morse Telegraph Samuel Morse, First electrical telegraph demonstrated in 1837

09-07-K.Steenhaut & J.Tiberghien - VUB 6 The Morse Telegraph Signal strength can be restored by means of electromechanical relays connecting separate telegraphic circuits. On land lines, unlimited distances can be covered, without increasing significantly the error rate.

09-07-K.Steenhaut & J.Tiberghien - VUB 7 The Telephone Graham Bell, 1876.

09-07-K.Steenhaut & J.Tiberghien - VUB 8 Analog vs. Digital Transmission Almost infinite number of states External perturbations can not be distinguished from original signal (superposed noise) Information degrades along the lines Finite, small, number of states Most external perturbations can be distinguished from original signal Information can be restored in relays 6:12 Analog Digital

09-07-K.Steenhaut & J.Tiberghien - VUB 9 Digital Techniques How are numbers represented in electronic devices ? Binary numbers (base 2) are used. A binary digit (bit) can be represented by a switch: –Value 0 : switch open –Value 1 : switch closed A number with n bits can take 2 n different values –2 bits : 4 combinations –3 bits : 8 combinations –8 bits (= 1 byte) 256 combinations –16 bits: combinations –24 bits: combinations –32 bits: combinations

09-07-K.Steenhaut & J.Tiberghien - VUB 10 Contents The 19th century telecommunications –Telegraph - Telephone –Digital vs. analog communications The voice networks & the data networks The electronics revolution ( ) –Digital sound –Mainframe computers with remote access –The first unification : ISDN –Local area networks –Wide area and local area networks integration The Internet –The research project –The universal computer communications medium –The successful unification ?

09-07-K.Steenhaut & J.Tiberghien - VUB 11 The Telephone Full mesh network Links = n*(n-1)/2

09-07-K.Steenhaut & J.Tiberghien - VUB 12 The Telephone With central switchboard Links = n

09-07-K.Steenhaut & J.Tiberghien - VUB 13 Automatic Exchange (1900) Conversation with switch operator replaced by signaling protocol - Voice: analog - Signaling: digital

09-07-K.Steenhaut & J.Tiberghien - VUB 14 The Telephone Network PABX SW PABX SW Trunk lines

09-07-K.Steenhaut & J.Tiberghien - VUB 15 Telex Networks ( ) Morse code replaced by Baudot or ASCII code

09-07-K.Steenhaut & J.Tiberghien - VUB 16 Alphabetical Codes A a B C D E 3 9 Morse ASCIIBaudot

09-07-K.Steenhaut & J.Tiberghien - VUB 17 Extended ASCII Character Set (8 bit)

09-07-K.Steenhaut & J.Tiberghien - VUB 18 Unicode (16 bit) FFFF 0000 ASCII Latin,Greek,Cyrillic, and Armenian Arabic and Hebrew Indic Punctuation, math, graphics Chinese / Japanese / Korean symbols Unified Chinese / Japanese / Korean ideographs Private applications

09-07-K.Steenhaut & J.Tiberghien - VUB 19 The Dual Networks Voice Network Analog+Digital Data Network Digital

09-07-K.Steenhaut & J.Tiberghien - VUB 20 Contents The 19th century telecommunications –Telegraph - Telephone –Digital vs. analog communications The voice networks & the data networks The electronics revolution ( ) –Digital sound –Mainframe computers with remote access –The first unification : ISDN –Local area networks –Wide area and local area networks integration The Internet –The research project –The universal computer communications medium –The successful unification ?

09-07-K.Steenhaut & J.Tiberghien - VUB 21 The Electronics Revolution ( ) Integrated circuits (“chips”) make electronics affordable. Mainframe computers become very powerful Mini & microcomputers become very popular Digital techniques offer better price/performance for sound applications

09-07-K.Steenhaut & J.Tiberghien - VUB 22 Music Records Analog Digital (CD) (44100 measurements/s)

09-07-K.Steenhaut & J.Tiberghien - VUB 23 Records with a scratch Analog Digital (CD) XXXX

09-07-K.Steenhaut & J.Tiberghien - VUB 24 Remote Access to Computers (1970) Star Network Mainframe Computer Dumb Terminals

09-07-K.Steenhaut & J.Tiberghien - VUB 25 Integrated Services Digital Network The first attempt to integrate voice and data Voice digitized at 64 Kb/s (8000 samples/s, 8 bit) Truly digital signaling A telephone connection = a 64 Kb/s digital link +A 64 Kb/s digital link is excellent for connecting a terminal to a mainframe computer -Connection time billing inadequate for data  ISDN widely used for telephony  ISDN marginal for data applications

09-07-K.Steenhaut & J.Tiberghien - VUB 26 Local Area Networks (1970) LAN’s initially introduced for Printer sharing File sharing...

09-07-K.Steenhaut & J.Tiberghien - VUB 27 The Dual Screen Desk (1980) WAN LAN

09-07-K.Steenhaut & J.Tiberghien - VUB 28 LAN-WAN Integration (1990) WAN LAN

09-07-K.Steenhaut & J.Tiberghien - VUB 29 Client - Server Systems Interconnection Network (LANs+WAN)

09-07-K.Steenhaut & J.Tiberghien - VUB 30 Client - Server Systems Benefits Sharing of storage –Access to common data –Professional back-up facilities –Centralized software (& data) maintenance Sharing of processing power –Unloading of central servers –Supporting local clients for exceptional needs Sharing of expensive peripherals

09-07-K.Steenhaut & J.Tiberghien - VUB 31 Terminal Emulation = sub-minimal Client-server system The personal workstations are used –as stand alone computers –as terminals connected to other computers The user has to mentally switch between widely different user interfaces and operating systems. Transferring data between local and remote applications is far from trivial Terminal emulation is very user unfriendly !!!

09-07-K.Steenhaut & J.Tiberghien - VUB 32 Virtual Mainframe = true Client-Server system The users interface of all applications runs on the personal workstations. For some applications, the workstation requests help from specialized servers. The user remains unaware of such requests. Servers can be optimized for specific tasks Virtual Mainframes can be –Very user friendly –cost effective

09-07-K.Steenhaut & J.Tiberghien - VUB 33 Three Tier Virtual Mainframes High-performance Local Area Network Back Office Corporate intranet or Internet Web servers + Access Control

09-07-K.Steenhaut & J.Tiberghien - VUB 34 Contents The 19th century telecommunications –Telegraph - Telephone –Digital vs. analog communications The voice networks & the data networks The electronics revolution ( ) –Digital sound –Mainframe computers with remote access –The first unification : ISDN –Local area networks –Wide area and local area networks integration The Internet –The research project –The universal computer communications medium –The successful unification ?

09-07-K.Steenhaut & J.Tiberghien - VUB 35 70’s: Need for Open Networks CCITT/ISO start standardization work for Open Systems Interconnection ARPA finances Research on open Network Technology: a Research WAN, ARPANET research on LAN interconnections Combination of the two ARPA efforts resulted in the INTERNET

09-07-K.Steenhaut & J.Tiberghien - VUB 36 The Early ARPANET (1976) Hawaii London Satellite link 56 Kbps terrestrial link Vince Cerf

09-07-K.Steenhaut & J.Tiberghien - VUB 37 The Results: TCP/IP + Set of Application Protocols –Set of communication “standards” allowing interoperability of almost all brands of computers. –Applicable to »Local Area Networks »Wide Area Networks »Interconnection of LAN’s through WAN’s The INTERNET –Communication facility for the Research Community –Financed by US government

09-07-K.Steenhaut & J.Tiberghien - VUB 38 The success story of TCP/IP To connect a computer to the ARPANET, TCP/IP is required ! Many different computers in use in Universities and research centers. TCP/IP becomes THE networking software available on ALL machines. Many stand-alone networks using TCP/IP appear due to the wide availability of TCP/IP and the many applications available for it.

09-07-K.Steenhaut & J.Tiberghien - VUB 39 The success story of ARPANET Universities where TCP/IP was developed start using the ARPANET backbone as a general purpose communication network. Other universities and research centers also want to get connected: with the help of the NSF, ARPANET becomes the North American Research Network. FREE access but “Acceptable Use Policy” imposed by ARPA on all users. Exponential growth of number of users Enormous help for US researchers.

09-07-K.Steenhaut & J.Tiberghien - VUB 40 Major Internet Changes DARPA is no longer the major funds provider. Apparition of the.COM domain Backbone operated by private companies and paid by the US-NSF and the connected networks. “Acceptable Use Policy” no longer required on the backbone, even if many of the connected networks still have one. Commercial “Internet Service Providers” build private networks to connect their subscribers to the Internet. The Internet has become a set of independently financed, cooperating regional networks.

09-07-K.Steenhaut & J.Tiberghien - VUB 41 Internet Cost Structure GIANT - Backbone infrastructure and neutral interconnects paid by interconnected networks, proportional to their access bandwidth. - Cost of direct interconnects shared by partners. - Not ACTUAL but POTENTIAL traffic is charged. USA Surfnet Planet Uunet NL Belnet eunet Skynet Planet Uunet BE

09-07-K.Steenhaut & J.Tiberghien - VUB 42 Firewalls = Intranet = Internet = Secure Intranet = Firewall

09-07-K.Steenhaut & J.Tiberghien - VUB 43 The Internet At last a successful integration of voice & data services ??? Internet has become almost as ubiquitous as the traditional telephone network. Internet cost structure based upon potential usage capabilities rather than actual usage. Larger and larger parts of the Internet have multi- media capabilities. Talking over the Internet becomes a realistic low- cost alternative to the traditional telephone service. Can the present Internet survive a victory over the traditional telephone operators ??? Will telephone operators themselves move their traffic to the Internet ???

09-07-K.Steenhaut & J.Tiberghien - VUB 44 The Multi-media challenge Voice & ImagesData Correctness:Non-essentialEssential Delay:Small & StableUnimportant The notion of “Quality of Service” Conclusion: Data and multi-media traffic have totally different requirements Mixing them on a single network is technically and economically challenging

09-07-K.Steenhaut & J.Tiberghien - VUB 45 Introduced concepts Digital vs. Analog communications –Analog signals degraded by noise –Digital signals can be restored to their original shape –Different requirements for data and multi-media Data transmission and Signaling –Signaling = management of the data transmission Client-server systems The Internet –A set of protocols –A set of interconnected networks Intranet –Part of the Internet behind a firewall.

09-07-K.Steenhaut & J.Tiberghien - VUB 46 Bibliography To know More about network modeling Andrew Tanenbaum Computer Networks and Open Systems Fourth Edition, Prentice Hall, ISBN

09-07-K.Steenhaut & J.Tiberghien - VUB 47 Bibliography Om meer te leren of computer netwerken (in dutch) Andrew Tanenbaum Computernetwerken Vertaling Fourth Edition Pearson Education Benelux ISBN X

09-07-K.Steenhaut & J.Tiberghien - VUB 48 Bibliography Pour en apprendre d'avantage sur les réseaux (in french) Andrew Tanenbaum Réseaux, 4e édition Pearson, 2003 ISBN