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Contents • The 19th century telecommunications – Telegraph - Telephone – Digital vs. analog communications • The voice networks & the data networks • The electronics revolution (1960-1980) – 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 ? Postacademic Interuniversity Course in Information Technology – Module C1 p1 70’s: 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 Postacademic Interuniversity Course in Information Technology – Module C1 p2 The Early ARPANET (1976) London Hawaii 56 Kbps terrestrial link Satellite link Postacademic Interuniversity Course in Information Technology – Module C1 p3 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 Postacademic Interuniversity Course in Information Technology – Module C1 p4 The success 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. Postacademic Interuniversity Course in Information Technology – Module C1 p5 The success 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. Postacademic Interuniversity Course in Information Technology – Module C1 p6 Major Internet Changes 1989-1992 • 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. Postacademic Interuniversity Course in Information Technology – Module C1 p7 Internet Cost Structure RARE NL USA Surfnet BE Belnet eunet Planet Planet Uunet Skynet Uunet • 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. Postacademic Interuniversity Course in Information Technology – Module C1 p8 Firewalls = Internet = Firewall = Intranet = Secure Intranet Postacademic Interuniversity Course in Information Technology – Module C1 p9 The Internet 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 ??? Postacademic Interuniversity Course in Information Technology – Module C1 p10 The Multi-media challenge The notion of “Quality of Service” Correctness: Delay: Data Essential Unimportant Voice & Images Non-essential Small & Stable Conclusion: Data and multi-media traffic have totally different requirements Mixing them on a single network is technically and economically challenging Postacademic Interuniversity Course in Information Technology – Module C1 p11 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. Postacademic Interuniversity Course in Information Technology – Module C1 p12