Chapter 7 Computer Networks and Internet PDF

Chapter 7 Computer Networks and Internet Introducing Computer Networks 2  Types of Computer Networks Local area network (LAN) ◼ Links computers within a building (close proximity). ◼ Uses direct cables, radio, or infrared signals....

Chapter 7 Computer Networks and Internet Introducing Computer Networks 2  Types of Computer Networks Local area network (LAN) ◼ Links computers within a building (close proximity). ◼ Uses direct cables, radio, or infrared signals. Metropolitan area network (MAN) Wide area network (WAN) ◼ Links computers within a ◼ Links computers group of buildings. separated by a few miles ◼ Uses fiber-optic cables. or thousands of miles. ◼ Uses long-distance transmission media. 3 Networking Synergies in a Nutshell Reduced hardware Shared applications costs ◼ Users share software ◼ Users share ◼ File server enables all equipment users to work with the same application Connected people program ◼ People can work together without being Building information at the same location resources ◼ Groupware enables ◼ Users create common sharing of schedules pools of data that can and communications be accessed by employees 4  Network Fundamentals ◼ Physical media used in networks: ❖ Cables– Telephone lines, coaxial cable, microwave, satellites, wireless, and fiber optic cables connect computers. ❖ Routers– Devices that examine the data transmitted and send it to its destination. ❖ Switches– High speed electronic switches maintain connections between computers. ◼ Protocols– Standards that specify how network components communicate with each other. 5 Copyright © 2003 Prentice Hall, Inc 6  Network Architecture ◼ Network architecture is the overall design of a network. ◼ The network design is divided into layers, each of which has a function separate from that of the other layers. ◼ Protocol stack– The vertical (top to bottom) arrangement of the layers. Each layer is governed by its own set of protocols. 7  Local Area Networks (LANs) ◼ LANs connect computers and peripherals within a building. ◼ Users can access software, data, and peripherals. ◼ LANs require special hardware and software. ◼ Computers connected to a LAN are called workstations or nodes. ◼ Different types of LANs: ❖ Peer-to-peer ❖ Client-server 8  LAN Hardware and Software Hardware ◼ Network interface card Software (NIC)– Inserted into a ◼ Operating system that computer’s expansion slot supports networking (Unix, Linux, Windows, Mac OS) ◼ Additional system software 9  Peer-to-Peer Networks ◼ All computers on the network are treated as equal. ◼ There are no file servers. ◼ Users decide which files and peripherals to share. ◼ They aren’t suited for networks with many computers. ◼ They are easy to set up. Example: Home networks 10  Client-Server Networks ◼ Typical corporate networks are client-server. ◼ They use various topologies or physical layouts. ◼ The network requires file servers, networked computers (clients), and a network operating system (NOS). ◼ Clients send requests to servers for programs and data, and to access peripherals. 11  Network Media LANs use a variety of media to carry network signals. ◼ Twisted pair–Two insulated wires twisted around each other. The same type of wire as that used for telephones. ◼ Coaxial cable– Consists of an insulated center wire surrounded by a layer of braided wire. The same type of wire as that used for cable TV. ◼ Fiber-optic cable– A type of fiber glass cable that transmits data in the form of light impulses. It can carry more data for longer distances than other wire. ◼ Infrared– A wireless system that includes a transmitter and receiver for sending and receiving signals. ◼ Radio– A wireless system that uses radio signals to send and receive data. 12  Types of Telephone Transmission Media Twisted Pair Copper Wire Fiber Optics Satellites Microwave 13  1960 1970 1980 1990 2000 Packet ARPANET TCPIP WWW Commercial Switching Internet History  LAN Topologies ◼ The physical layout of a LAN is called its topology. ◼ Topologies resolve the problem of contention, which occurs when multiple users try to access the LAN at the same time. ◼ Collisions or corrupt data occur when different computers use the network at the same time. Bus topology Star Ring topology ◼ All Called Contains workstations daisy a hub chain or attached central in a ◼ circular Every workstation wiring concentrator arrangement connected ◼Atospecial Easy a single to addunit bus workstations ofcable data called a ◼ token Resolves travels collisions aroundthrough the ring ◼ Workstations contention management can only ◼ transmit Difficult to data addwhen workstations they possess a token 19  Wide Area Networks (WANs) ◼ WANs are similar to long-distance telephone systems. ◼ They have a local access number called a point of presence (POP). 20  Point of Presence (POP) ◼ A point of presence is a WAN network connection point that enables customers to access the WAN by making a local telephone call. ◼ Media used to create a connection from an organization to a POP include: ❖ 56 Kbps leased line ❖ ISDN ❖ ADSL ❖ T1 line ❖ Permanent virtual circuit (PVC) 21  Bandwidth Transmission Media Bandwidth PSTN Twisted pair 56 Kbps ISDN 128 Kbps TV Cable 1 to 10 Mbps ◼ Bandwidth refers to the data transfer capacity of a transmission medium. ◼ It is measured in kilobits per second (Kbps), megabits per second (Mbps), or gigabits per second (Gbps). ◼ Broadband digital transmission refers to connection speeds of at least 1.5 Mbps. Copyright © 2003 Prentice Hall, Inc 22  Network Topology The physical layout of a network Node - each computer, printer, or server on network Three common topologies ◼ Star ◼ Ring ◼ Bus 23 Network Topology - Star ◼ - Uses Category 5 cable (cat 6 is used ◼ - Cat 5 cable uses an RJ-45 connector for the NIC card ◼ - Easy to install/not that expensive ◼ - Computers are concentrated into a star pattern using hubs or switches ◼ - Hubs broadcast data to all devices ◼ - Switches can be used instead of hubs ◼ - If there is a break in the cable it does not disturb the other computers 24 Network Topology - Ring ◼ - Uses different hardware ◼ - More expensive ◼ - Complex to install ◼ - Data is passed around the ring until it reaches its destination ◼ - Best at passing data with less collisions 25  Network Topology - Bus ◼ - Least expensive/easiest to setup ◼ - Uses coax cable ◼ - Computers are daisy chained together in a linear bus ◼ - Data packets are sent along the coax cables ◼ - All computers hear data sent out 26  internet A system that connects billions of computers around the world. A global network of hundreds of thousands of computers Widely considered to be the defining technology of the beginning of this century 28  Web Page Design HTML Document Authors use a markup language called Hypertext Markup Language (HTML) to create Web pages. 32  Page Document HTML Created 33  Web site A Web site is a collection of related Web documents that are made available to the public. The index page, or home page, is the first page of a Web site. 34  Web page A page on the internet with information and links to other pages.  Home Page The first/main page for a website. Or the default start page is the page that appears when the web browser starts. It can be customized.  Link Words you can click on to open another page  Text Box A white box in which you can type one line of text (a couple of words)  Text Area A white box in which you can type several/many lines of text  Drop Down Box A text box with an arrow at the end; click on it to see a list of choices  Back The icon that takes you to the last page you looked at  Search engine A web site that searches the internet for information you want Uniform Resource Locator (URL) Website address  File Transfer Protocol (FTP) A protocol for transferring files among computers. FTP servers maintain collections of downloadable files ◼ Downloading can often be done anonymously, without logging in 46