Algoritmer Gerth Stølting Brodal Institut for Datalogi Aarhus Universitet
Introduction to Networks and the Internet Bent Thomsen Institut for Datalogi Aalborg Universitet.
-
Upload
kasandra-marvel -
Category
Documents
-
view
216 -
download
2
Transcript of Introduction to Networks and the Internet Bent Thomsen Institut for Datalogi Aalborg Universitet.
Introduction to Networksand
the Internet
Bent Thomsen
Institut for Datalogi
Aalborg Universitet
October 2002 Bent Thomsen - FIT 2-1 2
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, email, file transfer, web browsers, ..
October 2002 Bent Thomsen - FIT 2-1 3
Small Local Networks
October 2002 Bent Thomsen - FIT 2-1 4
Local Area Networks
October 2002 Bent Thomsen - FIT 2-1 5
Large Local Area Networks
October 2002 Bent Thomsen - FIT 2-1 6
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
October 2002 Bent Thomsen - FIT 2-1 7
Direct connection
October 2002 Bent Thomsen - FIT 2-1 8
Client/Server connection
October 2002 Bent Thomsen - FIT 2-1 9
Web based client/server
October 2002 Bent Thomsen - FIT 2-1 10
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
October 2002 Bent Thomsen - FIT 2-1 11
The Internet is a collection of interconnected networks
October 2002 Bent Thomsen - FIT 2-1 12
Connecting to the Internet
• Through ISP– Modem dialup– Always-on: ADSL, Cable, FWA
• Direct/Dedicated network– Companies– Universities– (WLAN operators)
October 2002 Bent Thomsen - FIT 2-1 13
How to connect to the Internet
October 2002 Bent Thomsen - FIT 2-1 15
A bigger Internet backbone UUNet/WorldCom
October 2002 Bent Thomsen - FIT 2-1 16
Some Internet basics
• Each computer on the internet has a unique address – the IP address– 123.225.409.109– Most end-user computers are allocated an IP
address when they connect – DHCP– IP addresses can be given a name
• E.g www.but.auc.dk
• Looked up via DNS (130.225.56.21)
October 2002 Bent Thomsen - FIT 2-1 17
Package switched
October 2002 Bent Thomsen - FIT 2-1 18
Routing on the Internet
October 2002 Bent Thomsen - FIT 2-1 19
Things that may be in your way
• Operating system settings• Gateways• Firewalls• Proxy servers• Caches• Virus filters• Spam filters• Adult filters
October 2002 Bent Thomsen - FIT 2-1 20
Internet Applications
• Electronic mail (email)
• Mailing lists
• Newsgroups
• File Transfer
• Chat
• Instant Messaging
• World Wide Web
October 2002 Bent Thomsen - FIT 2-1 21
The World Wide Web
• 1991 The web (HTML/HTTP) - 1 web server
• 1993 The Mosaic Browser - 186 web servers
• 1994 Netscape – over 42000 web servers
• 1995 Internet Explorer - over 200000 web servers
• 1995 Java
• 1996 Browser wars – over 1 million web servers
• 1997 IE4
• 1998 XML and WAP – over 5 million web servers
• 1999 IE5
October 2002 Bent Thomsen - FIT 2-1 22
“a consensual hallucination experienced daily by billions of operators in every nation …”
Gibson
Cyberspace