computer network 2

Editor's Notes

• #2: Cisco Networking Academy Program IT Essentials: PC Hardware and Software v4.0 Chapter 8: Networks
• #3: Slide 3 - Chapter 8 Objectives The purpose of this chapter is to provide an overview of network principles, standards, and purposes. After completing this chapter, students will meet these objectives: Explain the principles of networking Describe types of networks Describe basic networking concepts and technologies Describe the physical components of a network Describe LAN topologies and architectures Identify standards organizations Identify Ethernet standards Explain OSI and TCP/IP data models Describe how to configure a NIC and a modem Identify names, purposes, and characteristics of other technologies used to establish connectivity Identify and apply common preventive maintenance techniques used for networks Troubleshoot a network
• #4: Slide 6 - Principles of Networking 8.1 Explain the principles of networking Networks are systems that are formed by links. Websites that allow individuals to link to each other’s pages are called social networking sites. A set of related ideas can be called a conceptual network. The connections you have with all your friends can be called your personal network. People use networks everyday. Examples of networks are a mail delivery system, a telephone system, a public transportation system, a corporate computer network, and the Internet. Computers can be linked by networks to share data and resources. A network can be as simple as two computers connected by a single cable or as complex as hundreds of computers connected to devices that control the flow of information. Converged data networks can include general purpose computers, such as PCs and servers, as well as devices with more specific functions, including printers, phones, televisions, and game consoles. All data, voice, video, and converged networks share information and use various methods to direct how this information flows. The information on the network goes from one place to another, sometimes via different paths, to arrive at the appropriate destination. The public transportation system is similar to a data network. The cars, trucks, and other vehicles are like the messages that travel within the network. Each driver defines a starting point (source) and an ending point (destination). Within this system, there are rules such as stop signs and traffic lights that control the flow from the source to the destination. After completing this section, students will meet these objectives: Define computer networks Explain the benefits of networking Teaching Strategy: The mail system allows messages to travel between any place that can be reached. The telephone system allows worldwide voice, fax, and Internet connections. Public transportation moves people and packages from source to destination. Each of these has a way of getting into and out of the network and a means of directing traffic. It is much the same with computer networks.
• #5: Slide 7 – Computer Networks 8.1.1 Define computer networks A computer data network is a collection of hosts connected by networking devices. A host is any device that sends and receives information on the network. Peripherals are devices that are connected to hosts. Some devices can serve either as hosts or peripherals. Computer networks are used globally in businesses, homes, schools, and government agencies. Many of the networks are connected to each other through the Internet. Network devices include: Desktop and laptop computers Printers and scanners PDAs and Smartphones File and print servers Resources shared across networks include: Services, such as printing or scanning Storage space on removable devices, such as hard drives or optical drives Applications, such as databases Network uses include: Access information stored on other computers Print documents using shared printers Synchronize the calendar between your computer and your smart phone Different types of network media: Copper cabling uses electrical signals to transmit data between devices Fiber-optic cabling uses glass or plastic wire, also called fiber, to carry information as light pulses Wireless connection uses radio signals, infrared technology (laser), or satellite transmissions
• #6: Slide 8 - Benefits of Networking 8.1.2 Explain the benefits of networks The benefits of networking computers and other devices include lower costs and increased productivity. With networks, resources can be shared, which results in less duplication and corruption of data. Fewer peripherals needed – Printers, scanners, and backup devices can be shared among the network users. Increased communication capabilities - Collaboration tools facilitate communicate between users; Examples: e-mail, forums and chats, voice and video, and instant messaging Avoid file duplication and corruption - Servers store data and share it with network users. Confidential or sensitive data can be protected and shared with the users who have permission to access that data. Document tracking software can be used to prevent users from changing files that others are accessing at the same time. Lower cost licensing – The site license allows a group of people or an entire organization to use the application for a single fee. Centralized administration - Fewer people needed to manage the network. Lower cost to the company. Easier data backup to a central location. Conserve resources - Data processing is distributed across many computers to prevent overloading one computer with processing tasks. Student Activity: The student course content includes a matching activity, 8.1.2 Advantages and Disadvantages of Networking. To complete this activity, students will identify each phrase as an advantage or a disadvantage.
• #7: Slide 9 - Types of Networks 8.2 Describe types of networks Data networks continue to evolve in complexity, use, and design. To communicate about networks, different types of networks are given different descriptive names. A computer network is identified by the following specific characteristics: The type of media used to connect the devices The type of networking devices used How the resources are managed How the network is organized How the data is stored The area it serves After completing this section, students will meet these objectives: Describe a LAN Describe a WAN Describe a WLAN Explain peer-to-peer networks Explain client/server networks
• #8: Slide 10 – Local Area Network (LAN) 8.2.1 Describe a LAN Local Area Network (LAN) refers to a group of interconnected computers that is under the same administrative control. In the past, LANs were considered to be small networks that existed in a single physical location. Although LANs can be as small as a single local network installed in a home or small office, over time, the definition of LANs has evolved to include interconnected local networks consisting of many hundreds of hosts, installed in multiple buildings and locations. All the local networks within a LAN are under one administrative control group that governs the security and access control policies that are in force on the network. In this context, the word “Local” in Local Area Network refers to local consistent control rather than being physically close to each other. Devices in a LAN may be physically close, but it is not a requirement.
• #9: Slide 11 – Wide Area Network (WAN) 8.2.2 Describe a WAN Wide Area Networks (WANs) are networks that connect LANs in geographically separated locations. A WAN covers a much larger area than a LAN. The most common example of a WAN is the Internet. The Internet is a large WAN that is comprised of millions of interconnected LANs. All of these networks are connected together using WAN connections, such as a phone company, cable company, or Internet Service Provider (ISP). Telecommunications service providers (TSP) are used to interconnect these LANs at different locations.
• #10: Slide 12 – Wireless LAN (WLAN) 8.2.3 Describe a WLAN Traditionally, in a LAN, devices are connected together using copper cabling. In some environments, installing copper cabling may not be practical, desirable, or even possible. In these situations, wireless devices are used to transmit and receive data using radio waves. These networks are called wireless LANs, or WLANs. In a WLAN, wireless devices connect to access points within a specified area. Access points are typically connected to the network using copper cabling. WLAN coverage can be limited to the area of a room or can have greater range. As with LANs, you can share resources such as files and printers, and access the Internet on a WLAN. Student Activity: The student course content includes a matching activity, 8.2.3 Network Types. To complete this activity, students will match each description to its network type. Teaching Strategy: The physical cables that connect devices in a LAN can be replaced by radio waves. In this case, a LAN becomes a Wireless Local Area Network (WLAN). A hotspot is the area where wireless access is available around a wireless access point. Hotspots can overlap, causing them to interconnect.
• #11: Slide 13 – Peer-to-Peer Networking 8.2.4 Explain peer-to-peer networks In a peer-to-peer network, devices are connected directly to each other without any additional networking devices between them. Each device has equivalent capabilities and responsibilities. Individual users are responsible for their own resources and can decide which data and devices to share. There is no central point of control or administration in the network. Peer-to-peer networks work best in environments with ten or fewer computers. Teaching Strategy: In a peer-to-peer network, networked computers act as equal partners, or peers, to each other. Individual users control their own resources. They may decide to share certain files with other users and may require passwords before they allow others to access their resources. Since individual users make these decisions, there is no central point of control or administration in the network. In addition, individual users must back up their own systems to be able to recover from data loss in case of failures. Peer-to-peer networks are relatively easy to install and operate. No additional equipment is necessary beyond a suitable operating system in each computer. Since users control their own resources, no dedicated administrators are needed. A peer-to-peer network works well with ten or fewer computers.
• #12: Slide 14 – Disadvantages of Peer-to-Peer 8.2.4 Explain peer-to-peer networks Peer-to-peer networks have several disadvantages: There is no centralized network administration which makes it difficult to determine who controls resources on the network. There is no centralized security. Each computer must use separate security measures for data protection. The network becomes more complex and difficult to manage as the number of computers on the network increases. There may be no centralized data storage. Separate data backups must be maintained. This responsibility falls on the individual users. Peer-to-peer networks still exist inside larger networks today. Even on a large client network, users can still share resources directly with other users without using a network server. In your home, if you have more than one computer, you can set up a peer-to-peer network.
• #13: Slide 15 – Client Server Network 8.2.5 Explain client/server networks In a client/server model, the client requests information or services from the server. The server provides the requested information or service to the client. Servers on a client/server network commonly perform some of the processing work for client machines; for example, sorting through a database before delivering only the records requested by the client. In a client/server model, the servers are maintained by network administrators. Data backups and security measures are implemented by the network administrator. The network administrator also controls user access to the network resources. All of the data on the network is stored on a centralized file server. Shared printers on the network are managed by a centralized print server. Network users with the proper permissions can access both the data and shared printers. Each user must provide an authorized username and password to gain access to network resources that they are permitted to use. For data protection, an administrator performs a routine backup of all the files on the servers. If a computer crashes, or data is lost, the administrator can easily recover the data from a recent backup. Teaching Strategy: As networks grow larger, peer-to-peer relationships become increasingly difficult to coordinate. They do not scale well, since their efficiency decreases rapidly as the number of computers on the network increases. Since individual users control access to the resources on their computers, security may be difficult to maintain. Client/server networks address these limitations of the peer-to-peer arrangement.
• #14: Slide 17 - Bandwidth 8.3.1 Explain bandwidth and data transmission Data is sent in small chunks called packets. A packet has a header, containing the source and destination of the packet. A header has sequencing information so that the packets can be assembled at the destination. Bandwidth is the amount of data that can be transmitted within a fixed time period. Bandwidth is measured in bits per second and is usually denoted by the following: bps - bits per second Kbps - kilobits per second Mbps - megabits per second Bandwidth can be compared to highway traffic flow On a highway, cars represent the data. Number of lanes represents the number of cars that could travel on the highway at the same time. An eight-lane highway allows four times as many cars as a two-lane highway.
• #15: Slide 18 – Three Modes of Transmission 8.3.1 Explain bandwidth and data transmission Data is transmitted in one of three modes: Simplex (Unidirectional transmission) is a single, one-way transmission. Example: The signal sent from a TV station to your TV. Half-duplex allows data to flow in one direction at a time. Simultaneous transmission in two directions is not allowed. Example: Two-way radios, police or emergency mobile radios Full-duplex allows data to flow in both directions at the same time. Bandwidth is measured in only one direction. 100 Mbps full-duplex means a bandwidth of 100 Mbps in each direction. A telephone conversation is an example of full-duplex communication. Both people can talk at the same time, and can still hear each other. Broadband technologies, such as digital subscriber line (DSL) and cable, operate in full-duplex mode. Broadband allows multiple signals to travel on the same wire simultaneously. Full-duplex networking technology increases network performance because data can be sent and received at the same time. Example: With DSL, users can download data and talk on the telephone at the same time.
• #16: Slide 26 – Internet Protocols 8.3.4 Describe Internet protocols and applications A protocol is a set of rules. Internet protocols are sets of rules governing communication within and between computers on a network. Protocol specifications define the format of the messages that are exchanged. Timing is crucial to network operation. Protocols require messages to arrive within certain time intervals so that computers will not wait indefinitely for messages that may have been lost. Therefore, systems maintain one or more timers during transmission of data. Protocols also initiate alternative actions if the network does not meet the timing rules. Many protocols consist of a suite of other protocols that are stacked in layers. These layers depend on the operation of the other layers in the suite to function properly. These are the main functions of protocols: Identifying errors Compressing the data Deciding how data is to be sent Addressing data Deciding how to announce sent and received data
• #17: Slide 31 – Physical Network Components 8.4 Describe the physical components of a network There are many devices that can be used in a network to provide connectivity. The device you use will depend on how many devices you are connecting, the type of connections that they use, and the speed at which the devices operate. These are the most common devices on a network: Computers Hubs Switches Routers Wireless access points The physical components of a network are needed to move data between these devices. The characteristics of the media determine where and how the components are used. These are the most common media used on networks: Twisted-pair copper cabling Fiber-optic cabling Radio waves After completing this section, students will meet these objectives: Identify names, purposes, and characteristics of network devices Identify names, purposes, and characteristics of the common network cables