Networks 1. Content. 3 Lectures on Networks Networks 1. Page 1

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1 Networks 1 Lecture Networks 1/Slide 1 Content 3 Lectures on Networks Networks 1 What is a Network? What is a Computer Network? Types of Networks Internet Who owns the Internet? The World Wide Web Mobile computing Cloud computing Lecture Networks 1/Slide 2 Page 1 1

2 Forthcoming Lectures Networks 2 How is Internet connected? How do networks work? Networks 3 What is a communications protocol? Network protocols Firewalls Network addresses Lecture Networks 1/Slide 3 Networks and graphs Network Graph Graph refers to the mathematical abstraction, while network to the real world instantiation Graphs are just collections of points joined by lines Points Lines vertices edges, arcs Math nodes links Computer Science sites bonds Physics actors ties, relations Sociology Lecture Networks 1/Slide 4 Page 2 2

denoting acquaintance. One could, in principle, construct the social network for a company or firm, for a school or university, or for any other community up to and including the entire world.

3 What is a social network? A social network is a collection of people, each of whom is acquainted with some subset of the others Represented as a set of points (or vertices) denoting people, joined in pairs by lines (or edges) denoting acquaintance. One could, in principle, construct the social network for a company or firm, for a school or university, or for any other community up to and including the entire world. Images of Networks: Lecture Networks 1/Slide 5 Computer Network A collection of computing devices connected in order to communicate and share resources Connections between computing devices can be Physical: wire or cables Wireless: radio waves or infrared signals Resources Computers Data and data storage Printing Lecture Networks 1/Slide 6 Page 3 3

Computer networks have opened up an entire frontier in the world of computing: client/server model Software systems often

4 Types of Communications Media Wire pairs Coaxial cables Fiber optics Microwave transmission Satellite transmission Wireless transmission Image: Computers - Tools for an Information Age Lecture Networks 1/Slide 7 Networking: Client/Server interaction Computer networks have opened up an entire frontier in the world of computing: client/server model Software systems often distributed across a network A client sends a request to a server for information or action (eg. file server, web server) Lecture Networks 1/Slide 8 Page 4 4

5 Networking: Terms Node (host): Any device on a network Data transfer rate (bandwidth): The speed with which data is moved from one place to another on a network Protocol: A set of rules that defines how data is formatted and processed on a network; i.e., rules that allow client/server interaction File server: A computer that stores and manages files for multiple users on a network Web server: A computer dedicated to responding to requests (from the browser client) for web pages Lecture Networks 1/Slide 9 Types of Network Networks can be classified according to their scale or scope Local-area network (LAN) connects a relatively small number of machines in a close geographical area Examples: A house, an office, or a whole building. Used in business and Universities. (STIRLAN) Metropolitan-area network (MAN) connects a larger geographical area such as a city or a region Example: Edinburgh and Stirling Metropolitan Area Network (EaStMAN) Wide-area network (WAN) Spans large geographical areas, such as a country Examples:» The UK research and education network (JANET) Internet: A wide area network that spans the planet! Lecture Networks 1/Slide 10 Page 5 5

6 LAN: Different Topologies Ring: Links all nodes in a circular chain. Msg around ring, single direction Star: Central (hub) computer manages network. Msg routed through hub Bus: All nodes connected to single line (bus). Msg. by bus in both directions What happens if one node fails? Ethernet: Industry standard for LANs. Uses either bus or star topology Lecture Networks 1/Slide 11 Connecting LAN Networks LANs connected across a distance to create a WAN Gateway: A Node that handles communication between its LAN and other networks Lecture Networks 1/Slide 12 Page 6 6

7 Our place in the networked world Heriot-Watt Stirling (MAN) Edinburgh The world Other UK uni (JANET) Imperial College London (INTERNET) Other UK uni Also see: Lecture Networks 1/Slide 13 The Internet A collection of Networks. The Internet is the network of networks Internet (hardware & protocols) vs. WWW (web of documents)! Origins and Initial Goal: US Military network for communications in the late 1960 s/early 1970s the ARPANET: a cold war spin-off Maintaining connectivity for military communications in the event of nuclear war. Redundancy: If some connecting links are destroyed, then other links exist that allow communication to be maintained 1990: The net became known as The Internet: Accessible to all! It has become bigger and bigger No-one is in charge of it No-one regulates it Lecture Networks 1/Slide 14 Page 7 7

8 Who owns the Internet? The Internet is a concept, not an actual physical entity It is made up of many smaller networks, and relies on an infrastructure to connect networks to other networks No single person or company owns the Internet or controls it entirely Several organizations, corporations, governments, schools, private citizens and service providers own pieces of the infrastructure, but nobody owns it all There are organisations that oversee and standardise Internet and assign IP addresses and domain names National Science Foundation, the Internet Engineering Task Force, ICANN, InterNIC and the Internet Architecture Board Lecture Networks 1/Slide 15 The World Wide Web The Web: An infrastructure of information (documents) combined and the software used to access it (interlinked h Web page: A document that contains or references various kinds of data Link: A connection between one web page and another Web Browser: Interface software used to explore the Internet Developed in British engineer Tim Berners-Lee Lecture Networks 1/Slide 16 Page 8 8

Mobile Computing Mobile web access is what most people mean by mobile computing.

mobile phone was the Nokia 9000 Communicator (1996) It weighed nearly 400g, had 8MB

9 Mobile Computing Mobile web access is what most people mean by mobile computing. It refers to access to the World Wide Web through portable devices, such as a mobile phone or tablet computer. The mobile web is the fastest growing aspect of the internet, especially in developing countries. Access to the mobile web is rapidly transforming the way that people live, all over the world. Image: blog.softwarehouse.co Lecture Networks 1/Slide 17 Mobile Computing (2) The first internet-enabled mobile phone was the Nokia 9000 Communicator (1996) It weighed nearly 400g, had 8MB memory and a 24MHz CPU, and costs 950 (or over 2000 at today s prices) A mid-range modern smartphone Blackberry Curve 9320 (2012) Weighs 103g, has 1GB internal memory and a 806MHz CPU, and costs about 50 (pay-as-you-go) now Lecture Networks 1/Slide 18 Page 9 9

Cloud Computing In traditional computing, your applications run on your own machine (word processing, spreadsheets, databases, email, etc) In Cloud Computing such applications are provided as

10 Cloud Computing In traditional computing, your applications run on your own machine (word processing, spreadsheets, databases, , etc) In Cloud Computing such applications are provided as services over the internet (Eg, Google Docs, Gmail, more sophisticated applications such as web portals, etc). The concept is quite old but has never really taken off until now This video explains the claimed benefits (note: it is a sales pitch and so it is biased) : YouTube video: What is Cloud Computing Lecture Networks 1/Slide 19 Cloud computing Lecture Networks 1/Slide 20 Page 10 10

11 Summary The notion of computer networks (nodes and links) Networking concepts and terms (client/server, protocol, etc.) Types of computer networks (LAN, MAN, WAN) LAN topologies (ring, star, bus) The Internet The World Wide Web Mobile computing Cloud computing Lecture Networks 1/Slide 21 Networks - References N. Dell & J. Lewis, Computer Science Illuminated, Chapters H.L Capron & J.A. Jhonson, Computers Tools for an information Age, Chapters 7-8 Levine et al The Internet for Dummies (10th edition). How Stuff Works - Internet Infrastructure: Gallery of Networks Next lecture: going deeper into how networks work Lecture Networks 1/Slide 22 Page 11 11

International Opportunities Fair Wednesday 5 th October 2016 Study Abroad Information Session LTA3 1.30pm 2.30pm International Opportunities Fair Atrium 2.30pm 4.

12 International Opportunities Fair Wednesday 5 th October 2016 Study Abroad Information Session LTA3 1.30pm 2.30pm International Opportunities Fair Atrium 2.30pm 4.30pm Study Abroad Information Session LTA3 4.30pm 5.30pm Study Live Learn Work Friends Worldwide opportunities Scholarships available Lecture Networks 1/Slide 23 Page 12 12

networks List various types of networks and their

Chapter 15 Networks Chapter Goals Describe the core issues related to computer networks List various types of networks and their characteristics Explain various topologies of local-area networks Explain