COMPSCI 111 / 111G An introduc)on to prac)cal compu)ng Introduc)on to Networking and the Internet 3/8/15 1
From the Telephone to the Internet 1876: First successful bi- direc;onal transmission of clear speech (Bell and Watson) 1940: First successful transmission of digital data through telephone (George S)bitz) http://en.wikipedia.org/wiki/history_of_the_internet! COMPSCI 111/111G! 2!
A culture of fear The Cold War (1947-1991) AFer World War 2 Iron Curtain between east and west Nuclear arms race between the US and USSR Space race Real fear of nuclear akack COMPSCI 111/111G! 3!
The technology race Huge investments for the military 1946 RAND 1958: Founda)on of the Advanced Research Projects Agency (ARPA) 1969: Bolt, Beranek, Newman Inc. (BBN) get contract to build the ARPANET, first ARPANET link between UCLA and Stanford Research Ins)tute Why ARPANET? Only limited number of powerful research computers in the country Researchers were geographically separated from the computers Switching nodes and network was unreliable, phone lines have a lot of sta)c COMPSCI 111/111G! 4!
Circuit- switching Used on tradi;onal (telephone) networks Centralized (central exchange nodes) Con)nuous connec)on formed Best for real- )me data (e.g. voice) B" A" COMPSCI 111/111G! 5!
Used for the Internet Packet- switching Decentralized (all nodes have equal authority) Messages broken into packets Each packet sent independently Nodes can route data packages efficiently to their des)na)on, avoiding broken/slow nodes on the way B" A" COMPSCI 111/111G! 6!
ARPANET 1969 The Beginning: ARPANET with 4 nodes 1972 ARPANET goes interna)onal 23 Nodes including London, Norway 1974 TCP/IP developed at Stanford COMPSCI 111/111G! 7!
ARPANET in 1977 COMPSCI 111/111G! 8!
Evolu;on of the Internet 1983 ARPA requires TCP/IP for Internet (high- speed backbone = 56 K bit per second) 1984 Domain Name System 1989 New Zealand connects to NSFNET 1991 WWW created at CERN (European Organiza)on for Nuclear Research) COMPSCI 111/111G! 9!
Internet Growth Year Hosts 1969 4 04/71 23 06/74 62 03/77 111 05/82 235 10/84 1,024 02/86 2,308 07/88 33,000 10/90 313,000 01/92 727,000 01/94 2,217,000 01/96 9,472,000 01/98 29,670,000 01/00 72,398,092 01/02 147,344,723 01/04 233,101,481 01/06 394,991,609 Number of hosts on logarithmic scale un)l 2012 http://www.isc.org/! COMPSCI 111/111G! 10!
World- wide users - 2008 Q2 http://www.internetworldstats.com/stats.htm! COMPSCI 111/111G! 11!
Internet Penetra;on - 2008 Q2 h]p://www.internetworldstats.com/stats.htm COMPSCI 111/111G! 12!
Local Area Network (LAN) Operates within 1 km radius Client- Server LAN Peer- to- peer LAN Network Categories Intranet (if set up like the internet) Wide Area Network (WAN) Distances over 1km An internet Several networks connected The Internet Network of networks that use TCP/IP COMPSCI 111/111G! 13!
Exercises 1) What is the difference between circuit switching networks and packet switching networks? 2) What was ARPANET? 3) Put the following events into chronological order: WWW created, Sputnik launched, DNS created,tcp/ip developed. 4) What is the difference between a LAN and a WAN? COMPSCI 111/111G! 14!
Internet Infrastructure How does it all work? Networking hardware Protocols Rules about how informa)on is transferred Domain Names Human- readable names for the computers on the Internet Client / Server SoFware Programs used to access the Internet http://computer.howstuffworks.com/internet-infrastructure.htm!
Protocols A protocol is a standardized methods of communica;on. On a network, both ends agree to use the same protocol to communicate. Protocols includes a set of rules and procedures for Ini)a)ng and maintaining communica)on Sending and receiving data Termina)ng communica)on http://en.wikipedia.org/wiki/protocol_%28computing%29! COMPSCI 111/111G! 16!
Some common protocols TCP / IP most important, used for transpor)ng data reliably UDP (user datagram protocol) used for transpor)ng data faster but less reliably FTP (file transfer protocol) used for transferring files HTTP (hyper text transfer protocol) used for client/ server communica)on, mostly web pages. POP3 / IMAP / SMTP used for email COMPSCI 111/111G! 17!
TCP/IP Transmission Control Protocol (TCP) Divides the message into packets Checks that all packets arrive (error detec)on) Makes sure that packets are not sent faster than they can be received (flow control) Combines packets to reform message Internet Protocol (IP) (version 4, version 6) Defines addresses for computers on the network (e.g. 130.216.34.102) Defines rou)ng informa)on Message TCP divides message 1 2 3 4 IP used to route TCP rebuilds message 2 3 4 1 5/03/12! COMPSCI 111/111G - Internet 01! 18!
Domain Names DNS Domain Name System Allows us to associate a human- readable name with an IP address Uses a sequence of names separated by periods Each domain name must be registered DNS server translates names into IP addresses Name! IP Address! Example: mary.auckland.ac.nz! DNS Server! 130.216.35.22! ama).emba.uvm.edu becomes 132.198.10.22 in version 4 example.com becomes 93.184.216.119 in version 4, and 2606:2800:220:6d:26bf:1447:1097:aa7 in IP version 6 http://en.wikipedia.org/wiki/domain_name! COMPSCI 111/111G! 19!
Networking Hardware Modem Modulator / Demodulator Dial- up Modems (up to 56Kbit per second) Broadband (DSL, digital subscriber line) modems (256 kbit/s to 20 Mbit/s) Allows communica)on via phone line. DSL uses high frequencies Router / Switch Connects mul)ple computers to a network Network Card Ethernet http://en.wikipedia.org/wiki/network_hardware! COMPSCI 111/111G! 20!
Internet Service Provider (ISP) Provide an Internet connec;on for you Set up an account for you Login Password Space set aside on their server (possibly) Email Web page Connec)on pool allows you to connect Give you an IP address Dynamic / Sta)c IP Modem! Modem! Other Servers, Intenet! ISP Server! Modem! COMPSCI 111/111G! 21!
Connec;ng to the Internet from home Dial- up (mostly obsolete) Computer Modem Phone line Computer! Modem! Phone Jack! COMPSCI 111/111G! 22!
Connec;ng to the Internet from home (2) Broadband Computer Network Card (ofen integrated), or use Wi- Fi Broadband Modem Possibly Filter Phone Line Computer! Network Card! Broadband! Modem! Filter! Phone Jack! COMPSCI 111/111G! 23!
Connec;ng to the Internet Home Network using Broadband Computer Network Card Broadband Modem Router / Switch Filter Phone Line Computer! Network Card! Computer! Network Card! Router /! Switch! Broadband! Modem! Filter! Computer! Network Card! Phone Jack! 5/03/12! COMPSCI 111/111G - Internet 01! 24!
The Next Step: Fibre Internet through fibre op)c cables: far greater speeds than copper cables Fibre in NZ (Ultra- fast broadband (UFB)) through government ini)a)ve Gradual rollout: schools, health providers, popula)on centres etc. has to be requested for last step to building Speeds in excess of 25Mbps currently up to 200 MB/s down, 50 MB/s up COMPSCI 111/111G! 25!
The Internet s backbone Very limited amount of undersea cables connects different parts At highest level owned by few carriers that rent out capacity Fragile COMPSCI 111/111G! 26!
Summary The Internet started as a military project to create a robust communica;on network Decentralized Packet- Switching The main protocol used on the Internet is TCP/IP Computers are iden)fied with IP addresses TCP takes care of reliable package transport IP provides addresses Domain names (human- readable) can be used instead of IP addresses Modems allow us to use phone lines to connect to the Internet COMPSCI 111/111G! 27!
More Exercises 5) What do network protocols do? 6) Give two examples of protocols used on the Internet and state what each protocol is used for. 7) Explain, in your own words, what a Domain Name Server does. 8) Imagine that a friend has three different computers in their home and they wanted to connect them all to the Internet. What hardware would you recommend that they purchase? Draw a diagram showing how the hardware would connect the machines to the Internet. COMPSCI 111/111G! 28!