IT – som værktøj Bent Thomsen Institut for Datalogi Aalborg Universitet
September 2003Bent Thomsen - FIT 1-12 Opgaver og øvelser fra sidst Web search Instant messaging Unix – X-win32 version LaTeX – brug Unix maskinen dolomit
Introduction to Networks and the Internet Bent Thomsen Institut for Datalogi Aalborg Universitet
September 2003Bent Thomsen - FIT 1-14 What is a network Carrier of data between connected computers What does a network consist of? –End hosts connected to the network –Physical links that carry data Ethernet, FDDI, ATM, … –Routers/switches –Protocols TCP/IP, HTTP, FTP, SMTP, … –Applications that communicate with each other Printing, , file transfer, web browsers,..
September 2003Bent Thomsen - FIT 1-15 Small Local Networks
September 2003Bent Thomsen - FIT 1-16 Local Area Networks
September 2003Bent Thomsen - FIT 1-17 Large Local Area Networks
September 2003Bent Thomsen - FIT 1-18 Client/Server networking Access large data sets and huge computing resources from desktop machines Separate data processing from presentation Facilitate several views on raw data Split workload between machines across a network –Do some processing locally and some on a server –Middleware and distributed objects
September 2003Bent Thomsen - FIT 1-19 Direct connection
September 2003Bent Thomsen - FIT Client/Server connection
September 2003Bent Thomsen - FIT Web based client/server
September 2003Bent Thomsen - FIT The Internet A set of connected networks –All use the same network protocol (IP) Most common protocol used is TCP/IP –Connection oriented –Reliable, in-order byte-stream Application protocols on top of TCP/IP –SMTP –HTTP –FTP UDP is another protocol –Used for streaming video and audio –Some peer-to-peer applications Protocols define format, order of messages and actions taken on messages
September 2003Bent Thomsen - FIT The Internet is a collection of interconnected networks
September 2003Bent Thomsen - FIT Connecting to the Internet Through ISP –Modem dialup –Always-on: ADSL, Cable, FWA Direct/Dedicated network –Companies –Universities –(WLAN operators)
September 2003Bent Thomsen - FIT How to connect to the Internet
September 2003Bent Thomsen - FIT An Internet Backbone
September 2003Bent Thomsen - FIT A bigger Internet backbone UUNet/WorldCom
September 2003Bent Thomsen - FIT Some Internet basics Each computer on the internet has a unique address – the IP address – –Most end-user computers are allocated an IP address when they connect – DHCP –IP addresses can be given a name E.g Looked up via DNS ( )
September 2003Bent Thomsen - FIT Package switched
September 2003Bent Thomsen - FIT Routing on the Internet
September 2003Bent Thomsen - FIT Things that may be in your way Operating system settings Gateways Firewalls Proxy servers Caches Virus filters Spam filters Adult filters
September 2003Bent Thomsen - FIT Internet Applications Electronic mail ( ) Mailing lists Newsgroups File Transfer Chat Instant Messaging World Wide Web
September 2003Bent Thomsen - FIT The World Wide Web 1991 The web (HTML/HTTP) - 1 web server 1993 The Mosaic Browser web servers 1994 Netscape – over web servers 1995 Internet Explorer - over web servers 1995 Java 1996 Browser wars – over 1 million web servers 1997 IE XML and WAP – over 5 million web servers 1999 IE5
September 2003Bent Thomsen - FIT “a consensual hallucination experienced daily by billions of operators in every nation …” Gibson Cyberspace