IST 220-002: Networking and Telecommunications Chapter 1: Introduction to Computer Networks & Data Communication

1. IST 220-002: Networking and TelecommunicationsChapter 1: Introduction to Computer Networks & Data Communication Dr. Lee Giles 001 Thomas Building, School of IST Phone 865 7884 Email: giles@ist.psu.edu

2. What is Information Technology (IT)? Information Technology (IT) Computer Technology Communication Technology To collect, store, process, search, retrieve, and present electronic information to meet the needs of various kinds of users, e.g., computer hardware & software, PDAs, printers, groupware, smart cards…. To deliver, disseminate, exchange, transmit, and receive electronic information in local, regional or global contexts, e.g., networks, fax machines, cell phones, email, satellites, GPS, Internet, telephony, ….

3. Computer Systems Redefined Computer systems used to be defined as: hardware software + Computer systems are now redefined as: hardware software networks + +

4. Information & Communication • Generation and transfer of information is critical to today’s businesses • Flow of information both mirror and shape organizational structures • Networks are the enabling technology for this process

5. The “Manager’s Dilemma” • Technology is necessary for competitiveness • Cost of technology has decreased • Reliance on technology has increased • Number of choices have increased • Choices are both more difficult and more important

6. What is Data Communication? • Communication of data between sources • Data formats – analog or digital or both • Data travels by a medium • Wires • Space

7. Essentials of Data Communication • Message • Sender • Receiver • Medium • Understandability • Error detection • Security

8. Types of Messages

9. Protocols • Enables communication – how we communicate (convention used for establishing transmission rules) • When • Where • How • What with • How much

10. Protocols

11. Important Dates in the History of Data Communications (1) • 1837 – Invention of the telegraph • 1876 – Invention of the telephone • 1947 – Invention of the transistor (replaced vacuum tubes) • 1948 – First commercial computer installed, the UNIVAC I • 1958 – First U.S. Communications satellite sent into orbit • 1959 – FCC approves private microwave communications networks • 1964 – Packet switching network concept proposed by the Rand Corporation • 1966 – IBM's binary synchronous (BISYNC or BSC) protocol announced • 1969 – ARPANET, first packet switching network (later to become the Internet), begins operation

12. Important Dates in the History of Data Communications (2) • 1972 – Ethernet local area network specifications formulated • 1972 – IBM's Synchronous Data Link Control (SDLC) protocol announced • 1974 – IBM announces its Systems Network Architecture (SNA) • 1975 – Personal computers introduced, the Altaire 8800 replaced terminals in many cases • 1981 – IBM PC introduced • 1985 – Cellular radio telephones are introduced • 1990 – World Wide Web is introduced • 1993 – Web search engines introduced • 1995 – The Internet grows to over four million host computers • 1999 – The Internet grows to over ten million host computers

13. Data Communication Applications (1) • Batch - bi-directional transfers of large amounts of data in concentrated groups • Data Entry - Lengthy inputs with short responses • Distributed - data and/or processing is handled by more than one processing unit • Inquiry/Response - Small inputs of data that may result in large responses

14. Data Communication Applications (2) • Interactive - Short inputs and outputs. Real-time response with direct user interaction • Sensor-Based - Input derived from sensors instead of human operators • Combined - More than one of the above applications running at the same time

15. What is a Computer Network? Two or more computers or communications devices connected by transmission media and channels and guided by a set of rules for communication purposes that allow users to communicate with each other and share applications and data. • Hardware: • Computer • Network card • Routers • Modem … • Media: • Cable • Wire • Microwave … Components of a Computer Network • Software: • Network OS • Utilities … • Network Design: • Logical layout • Physical layout …

16. Applications of a Computer Network • Mass transit • Interstate highways • 24-hour bankers, grocery stores • Cable television • Pagers • Mobile telephones • Most businesses and schools • Retail outlets • …

17. Network Essentials Models • Client/Server • Peer-to-Peer Technologies Types • Ethernet • Token Ring • Transmission Control Protocol/Internet Protocol (TCP/IP) • Wireless Application Protocol (WAP) • Local Area Network (LAN) • Metropolitan Area Network (MAN) • Wide Area Network (WAN) Network OS Topologies • Bus Topology • Ring Topology • Star Topology

18. Network Technologies • Based on bus topology; but can be used in star topology; • Higher speed: first Fast Ethernet, then Gigabit Ethernet; • Most popular: inexpensive, easy to install and maintain. Ethernet • Based on a ring topology; but can use a star topology; • Token-passing scheme to prevent collision of data; • The second most widely-used protocol after Ethernet. Token Ring • Based on client/server model of network computing; • Uses packet switching technique for data transmission; • Commonly used for Internet applications. TCP/IP • Uses client/server model of network computing; • Allows wireless devices to access the Internet and WWW; • Meets increasing demands for wireless Internet access. WAP

19. The World of Connectivity Wired or wireless communications links offer several options for information and communications. Source: The McGraw-Hill Companies, Inc., 1999

20. Computer Network Configurations:Connections between Networks • Computer terminal to mainframe computer • Microcomputer to mainframe computer • Microcomputer to local area network • Microcomputer to Internet • Local area network to local area network • Local area network to wide area network • Sensor to local area network • Satellite and microwave • Wireless telephone

21. Computer Network Configurations:Computer Terminal to Mainframe Computer • Used in many types of businesses for data entry and data retrieval. • Usually involves a low-speed connection.

23. Computer Network Configurations: Microcomputer to Local Area Network • Very common throughout business and academic environments. • Typically a medium- to high-speed connection.

25. Computer Network Configurations:Microcomputer to Internet • Very popular with home users. • Typically a modem is used to connect user’s microcomputer to an Internet Service Provider. • Newer technologies such as DSL and cable modems are replacing modems.

27. Computer Network Configurations:LAN to LAN Connections • Found in businesses and schools that have two or more LANs and a need for them to intercommunicate. • The bridge is a typical device used to interconnect LANs.

28. Data Communications and Computer Networks Chapter 1

29. Computer Network Configurations:LAN to WAN Connections • One of the best ways to interconnect a user on a workstation to the Internet (a wide area network). • A router is the typical device that performs LAN to WAN connections.

31. Computer Network Configurations:Sensor to LAN Connections • Often found in industrial environments. • Assembly lines and robotic controls depend heavily on sensor-based local area networks.

33. Computer Network Configurations:Satellite and Microwave • Many types of applications including long distance telephone, television, radio, long-haul data transfers, and wireless data services. • Typically expensive services but many companies offer competitive services and rates.

35. Computer Network Configurations: Wireless Telephone • Quickly expanding market across the U.S. and world. • First generation analog services and second generation PCS services available in most areas and under many types of plans. • Third generation services beginning to appear in Europe and Asia.

37. Why Are Networks Important? • Enterprise • Organization • Department • Individual Users • LANs • Mans • WANs BUSINESS ENTERPRISE Network Applications Internet • Functions • Organizational • Processes • Personal • Wired • Wireless Information • Traditional Data • Text • Images • Graphics • Voice • Video • Multi-media

38. Networks: Pros and Cons Pros Cons • Resource sharing • Printers, CD-ROMs, computers • Data and information sharing • Communications • Reduced Cost • On-line services • Groupware • Software that supports group efforts over a network • Electronic data interchange • Security risks increase with networks • Complexity is associated with networks • Investment is high and return on it may not happen

39. Access to the Internet Network Access Wired access Cable modem DSL Wireless access Wireless LAN RosettaNet – XML based Network security Goals and Measures Firewalls Key Issues of Networks

40. Why Use a Network? • Sharing of • Data, messages, graphics … • Applications … • Devices, e.g., hard drives, backups, printers, modems, fax machines … • Centralized administration • Installing and upgrading application software • Communication and collaboration • Teleconferences, group decision support systems

41. Class Discussion • If you could design your own home, what kinds of computer network or data communications labor-saving devices would you incorporate? • Using a laptop computer with a wireless connection into the company’s local area network, you download a Web page from the Internet. List all the different network configurations involved in this operation.

42. Language of Computer Networks • Important terms and concepts.

43. Components of a Network • Server • A computer that provides services to other networked computers • Client • A computer in a client/server relationship, e.g., a Web browser • Hardware/Software • Network card, router, modem, hub/NT operating systems, utilities … • Media • The way to connect computers on a network • Data • Files o be shared by network computers • Resources • Peripherals, e.g., printers, to be used bynetwork computers

44. Media of Networking • Coax cable • Twisted pair cable • Fiber optic cable • Microwave • Communications satellite • Cellular phones

45. Networking Hardware • Workstations • Servers • Bridges • Routers • Hubs and switches • Nodes

46. Network Models Client/Server Model Microcomputer users, or clients, share services of a centralized computer called a server. Peer-to-Peer Model Computers share equally with one another without having to rely on a central server.

47. Client/Server A distinction exists between computers that make available network resources (servers) and those computers that use the resources (clients or workstations). Pros: • Very secure • Centralized servers easy to manage • Physically centralized • Secure OS • Better performance • Centralized backups • Reliability • Simple job to do plus built in redundancy Cons: • Require professional administration • More hardware intensive

48. Peer-to-Peer (p2p) Computers on the network communicate with each others as equals and each computer is responsible for making its own resources available to other computers on the network. Pros: • Uses less expensive computer networks • Easy to administer • No NOS (network operating system) required • More built-in redundancy • Shared resources – some machine will have what you need Cons: • Individual user performance easily affected • Not very secure • Tragedy of the commons – no guarantee others will administer their resources properly (almost guaranteed with over 10 machines) • Hard to back up.

49. Client/Server vs.Peer-to-Peer: Advantages and Disadvantages Client/Server Model Peer-to-Peer Model Advantages: • Very secure OS. • Better performance. • Centralized servers, easy to manage. • Centralized backups. • High reliability. Advantages: • Uses less expensive networks. • Easy to administer. • Contain both network operating system and application software. • Ideal for small business and home users. Disadvantages: • Individual user performance easily affected. • Not very secure. • Hard to back up. Disadvantages: • Expensive administration. • More hardware intensive.

50. Networking Essentials • Computer Networks • A host computer connected with communication circuits and equipment to terminals • Two or more computers connected via a communication medium • Intranet • A private version of the Internet • Enterprise Network • Two or more LANs connected to each other, or one or more LANs connected to a WAN • File Server • A computer that contains files shared by PCs on a network