Introduction to Computer Science

1. Introduction to Computer Science Networks Lecture a This material (Comp 4 Unit 6) was developed by Oregon Health & Science University, funded by the Department of Health and Human Services, Office of the National Coordinator for Health Information Technology under Award Number 90WT0001. This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/4.0/.

2. Learning Objectives - 1 • Define what a communication network is (Lecture a) • Explain the purposes and benefits of a communication network. (Lecture a) • Explain the Internet and World Wide Web, their histories, and their structures. (Lecture a) • Describe different ways of connecting to the Internet. (Lecture a)

3. Learning Objectives - 2 • Explain the basics of network addressing • Internet Protocol (IP) addresses • Domain names • Lease vs. purchase from an Internet service provider (Lecture b) • Introduce network classification by the coverage size. (Lecture b)

4. Learning Objectives - 3 • Describe different network topologies. (Lecture c) • Outline different standards and protocols that govern wired and wireless communications. (Lecture c)

5. Learning Objectives - 4 • Describe benefits and disadvantages of wireless communication (Lecture d) • Describe a typical wireless network setup. (Lecture d) • Describe network hardware. (Lecture d) • Introduce networking logical models and discuss Open Systems Interconnection (OSI) model. (Lecture e)

6. What is a Network – Wikipedia • “…a collection of computers and devices connected by communications channels that facilitates communications among users and allows users to share resources with other users.” (Wikipedia, 2011)

7. What is a Network – In Plain English • A network is made up of computers, printers, other devices, and some sort of media (cabling, wireless) that allows all of these devices to communicate with each other

8. Modern Network Example A site-to-site network with support for remote users Ludovic.ferre, 2010, CC BY-SA 3.0

9. Why Networks? • Share hardware • Printer, scanner, data storage devices • Share software • Software installed on a server to reduce cost • Share files • Images, spreadsheets, documents • Communicate • E-mail, network phones, live chat, instant messaging

10. Networks Decrease Cost • Printed documentation moved to a web server • No longer need to update physically. Can update web page and notify users of changes • E-mail done electronically and replaces paper documents • Easier to keep device software current • No need to physically visit each device to manage it or upgrade software

11. Networks Serve Customers • Documentation can be posted and maintained online • Customers can chat or e-mail with customer service reps • Customer service reps have access to a common network database containing solutions to common customer requests or issues

12. Networks Serve Patients • Hospitals can store all patient data in one common network database, improving quality of care • Medical staff and patients can access electronic medical records stored in a network database • Patients can also access important data

13. What is the Internet? • “The Internet is a global system of interconnected computer networks that use the Internet protocol suite (TCP/IP) to link billions of devices worldwide.”(Wikipedia, 2016) • In other words, the Internet is a large network made up of many smaller networks

14. The Origins of the Internet -1 • The Internet originated in the 1960s from a project commissioned by the governments of the USA, UK, and France to build robust, fault-tolerant communication • First network in the United States was ARPANET: Advanced Research Projects Agency Network

15. The Origins of the Internet -2 • In 1969, the original Internet consisted of four computers (servers): • University of California, Los Angeles (UCLA) • University of California, Santa Barbara • Stanford Research Institute • University of Utah

16. The Internet Today • Internet continues to grow, especially since the mid-1990s • In 1995, approximately 16 million people were using the Internet • In 2015 about 3.17 billion people were using the Internet (International Telecommunication Union)

17. The Internet Spawns the World Wide Web - 1 • Internet and World Wide Web often used interchangeably, but they are not the same. • “The World Wide Web is an information space where documents and other web resources are identified by URLs, interlinked by hypertext links, and can be accessed via the Internet.” (Wikipedia, 2016)

18. The Internet Spawns the World Wide Web - 2 • A URL (uniform resource locator) is an address typed into a browser’s address line, such as www.whitehouse.gov.

19. Who Created the Web? • British scientist Tim Berners-Lee is credited with creating the Web in 1989 by introducing a web browser and web page coding Bojārs, U., 2005, CC BY 2.0

20. How Does the Web Work? • Browser: • A software program that connects to web servers over the Internet • Uses hypertext transfer protocol (HTTP)to communicate with web servers to get web page content • Web server send hypertext markup language (HTML) coding back to the browser, which translates that coding for display on a monitor

21. HTML - The Language of the Web • Web pages are text files written in the HTML programming language • HTML example for a simple web page 2.1 Figure: Diagram of an HTML example for a simple web page. (PD-US, 2010)

22. Who Owns the Web? • No entity owns the Internet • Individuals and organizations own the devices that connect to the Internet • These people and organizations also own the content of the Web • For example, Google’s experience in China • See Wikipedia’s web page titled “Internet Censorship in China”

23. Internet Service Providers • Users connect to the Internet via Internet Service Providers (ISPs) • ISPs are organized as local, regional, and national providers Ludovic.ferre, 2010, CC BY-SA 3.0

24. Data Transmission Rate – Bandwidth • The data transmission rate (speed) of a network is characterized by bandwidth and throughput • Bandwidth is the highest amount of data that can be carried between two points in a given time period (usually one second) • Usually expressed in bits per second (bps), megabits per second (Mbps), or gigabits per second (Gbps)

25. Data Transmission Rate – Bandwidth and Throughput • The data transmission rate (speed) of a network is characterized by bandwidth and throughput • Bandwidth is the highest amount of data that can be carried between two points in a given time period (usually a second) • Throughput is the amount of bandwidth available for network communications

26. Data Transmission Rate – Network Performance • Network performance can be degraded by a number of factors: • Required network traffic • Packet loss • Latency • Example • If bandwidth on your cabled network is 100 Mbps, throughput is usually about 70 Mbps due to communication overhead

27. How Devices Connect to a Network • Wired or wireless connections • Network may or may not be connected to the Internet • An Internet connection requires an ISP • An Intranet is a private network and does not connect to the Internet • Accessible only by the devices within organization • May connect various offices together, regardless of their location, without providing Internet access

28. Wired Connection Types • Dialup: Copper phone lines connected to an ISP’s modem • Limited to 56 Kbps, slowest connection type • Broadband: Higher quality copper phone lines or coaxial cable • Faster than dialup: ~768 Kbps and higher • Fiber optic: Transmitting pulses of light through an optical fiber • ~ 500 Mbps

29. Wireless Connections • Wi-Fi: Local Area Networking (LAN) • Connects laptops and mobile devices to a wireless access point (WAP), which in turn connects to the Internet through a wired network • Used extensively by hotels and airports • Speeds range from 1 Mbps to 200+ Mbps, depending on a variety of factors • Satellite: Uses communication satellites • Speed ~ 50 Mbps

30. Wireless Telephone Technology - 1 • 1G, 2G, 2.5G, 3G, 4G, 5G are different generations of wireless telephone technology • 3G: Third generation technology introduced in 2001 • Data transmission speed is up to 2Mbps • High-speed web • Video conferencing • TV streaming • WCDMA standard

31. Wireless Telephone Technology - 2 • 4G: Fourth generation, introduced in 2008 • Capable of providing 100Mbps – 1Gbps speed • Mobile Multimedia • Customized Personal Services • WiMAX and LTE standards • 5G: Next major step in the evolution of mobile telecommunications • Currently (2016) undergoes testing • Expected to be widely available by 2020

32. NetworksSummary – Lecture a • Defined communication network and explained its purposes and benefits • Explained Internet and WWW, their histories, and their structures • Described different ways of connecting to Internet

33. NetworksReferences – Lecture a References Wikipedia. [Internet]. Available from: http://en.wikipedia.org/wiki/Computer_network. Accessed 2011. Images Slide 8: Site-to-site Network Topology [image on the Internet]. Ludovic.ferre (22 April 2010) [cited 2011 Nov 07]. Retrieved Jan 2012 from: http://en.wikipedia.org/wiki/File:Virtual_Private_Network_overview.svg. Licensed through Creative Commons Attribution-ShareAlike 3.0 Unported License Slide 19. Tim Berners-Lee at a Podcast Interview [image on the Internet]. UldisBojārs (18 November 2005) [cited 2017 March 01]. Retrieved March 2017 from: https://commons.wikimedia.org/wiki/File:Tim_Berners-Lee.jpg. Licensed through Creative Commons Attribution-Share Alike 2.0 Generic Slide 23: Tier 1 and 2 ISP Interconnections [image on the Internet]. Ludovic.ferre (16 April 2010 ) [cited 2011 Nov 07]. Retrieved Jan 2012 from: http://en.wikipedia.org/wiki/File:Internet_Connectivity_Distribution_%26_Core.svg. Licensed through Creative Commons Attribution-ShareAlike 3.0 Unported License

34. Introduction to Computer Science NetworksLecture a This material was developed by Oregon Health & Science University, funded by the Department of Health and Human Services, Office of the National Coordinator for Health Information Technology under Award Number 90WT0001.