Technology in Action Chapter 12 Behind the Scenes: Networking and Security in the Business World This chapter takes you behind the scenes of networking.

Alan Evans • Kendall Martin
Technology in Action Alan Evans • Kendall Martin Mary Anne Poatsy Ninth Edition Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Technology in Action Chapter 12 Behind the Scenes: Networking and Security in the Business World This chapter takes you behind the scenes of networking principles. We look at how client/server networks work and examine exactly how these networks are designed and built. We discuss the various kinds of servers used in such networks as well as the layout and equipment used to create them. Finally, we discuss how large networks are kept secure. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Chapter Topics Networking advantages Client/Server Networks
Classifications of Client/Server Networks: LANs, WANs, MANs, and PANs Servers Network Topologies Chapter topics include: Networking advantages Client/Server Networks Classifications of Client/Server Networks: LANs, WANs, MANs, and PANs Servers Network Topologies Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Chapter Topics (cont.) Transmission Media Network Operating Systems
Network Adapters Network Navigation Devices Network Security for Client/Server Networks Chapter Topics (continued) Transmission Media Network Operating Systems Network Adapters Network Navigation Devices Network Security for Client/Server Networks Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Networking Advantages
Network is group of two or more computers Networks: Increase productivity Enable expensive resources to be shared Facilitate knowledge sharing Enable software sharing Facilitate Internet connectivity Enable enhanced communication A network is a group of two or more computers (or nodes) that are configured to share information and resources such as printers, files, and databases. Essentially, a network enables computers and other devices to communicate with each other. Large business networks provide advantages similar to those of home networks, and therefore have advantages over individual stand-alone computers: Networks increase productivity. Computers are powerful stand-alone resources. However, to increase productivity, people need to be able to share data and peripherals with co-workers and communicate with them efficiently. Without a network, only one person at a time can access information because it resides on a single computer. Information sharing is therefore the largest benefit gained by installing a network. Networks enable expensive resources to be shared. Networks enable people to share peripherals such as printers, eliminating the need for duplicate devices. Without a network, the printer would have to be connected to one of your computers. Think about how often a printer sits idle. Compound that by having 25 students in a lab, all with their own printers. Having 25 printers sitting idle 95 percent of the time is a tremendous waste of money. Installing a network that enables one printer (working most of the time) to serve all 25 students saves money. Networks facilitate knowledge sharing. The databases you learned about in Chapter 11 become especially powerful when deployed on a network. Networked databases can serve the needs of many people at one time and increase the availability of data. Your college’s databases are much more useful when all college employees can look up student records at the same time. Networks enable software sharing. Installing a new version of software on everyone’s desktop in a college with 700 employees can be time consuming. However, if the computers are networked, all employees and students can access the same copy of a program from the server. Although the college must still purchase a software license for each user, with a network it can avoid having to install the program on every computer. This also saves space on individual computers, because the software doesn’t reside on every computer. Networks facilitate Internet connectivity. Most college students and employees need to connect to the Internet to complete work. Providing each computer on a network with its own dedicated connection to the Internet is costly. Through a network, large groups of computers can share one Internet connection, reducing Internet connectivity expenses. Networks enable enhanced communication. Social networking tools, , and instant messaging are extremely powerful applications when deployed on a network (especially one that is connected to the Internet). College students and professors can easily exchange information with each other and can share valuable data by transferring files to other users. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Networking Disadvantages
Business networks are often complex Require additional personnel to maintain them Require special equipment and software Most companies feel cost savings outweigh additional cost of network administrators and equipment Because business (or college) networks are often complex, additional personnel are usually required to maintain them. These people, called network administrators, have training in computer and peripheral maintenance and repair, networking design, and the installation of networking software. Another disadvantage is that operating a network requires special equipment and software. However, most companies feel that the cost savings of peripheral sharing and the ability to give employees simultaneous access to information outweigh the costs associated with network administrators and equipment. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Client/Server Networks
Client/server networks contain servers as well as client computers Server is computer that stores and shares resources on a network Client is computer that requests those resources Servers respond to requests from large number of clients The majority of computer networks are based on the client/server model of computing. As you’ve learned, a server is a computer that both stores and shares resources on a network, whereas a client is a computer that requests those resources. A client/server network (also called a server-based network) contains servers as well as client computers. The inclusion of servers is what differentiates a client/server network from a typical peer-to-peer (P2P) network. Each node connected to a P2P network can communicate directly with every other node on the network instead of having a separate device exercise control over the network. The main advantage of a client/server relationship is that it makes data flow more efficiently than in peer-to-peer networks. Servers can respond to requests from a large number of clients at the same time. In addition, servers can be configured to perform specific tasks (such as handling or database requests) efficiently. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Classifications of Client/Server Networks
Networks are classified according to size and distance between physical parts Four popular classifications: Local area networks (LANs) Wide area networks (WANs) Metropolitan area networks (MANs) Personal area networks (PANs) Networks are generally classified according to their size and the distance between the physical parts of the network. Four popular classifications are local area networks, wide area networks, metropolitan area networks, and personal area networks. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Local Area Networks LAN
Group of computers and peripherals linked together over a small geographic area Computer lab at school is probably a LAN A local area network (LAN) is a (generally small) group of computers and peripherals linked together over a relatively small geographic area. The computer lab at your school or the network serving the floor of the office building where you work is probably a LAN. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Wide Area Networks WANs comprise large numbers of users over a wider physical area Businesses use WANs to connect two or more geographically distant locations Separate LANs that are miles apart Wide area networks (WANs) comprise large numbers of users over a wider physical area or separate LANs that are miles apart. Businesses often use WANs to connect two or more geographically distant locations. For example, a college might have a west and an east campus that are located in two different towns. The LAN at the west campus is connected to the LAN at the east campus, forming one WAN. WANs are connected either by dedicated telecommunications lines or by satellite links. Students on both campuses can share data and collaborate through the WAN. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Metropolitan Area Networks
Organizations or groups establish WANs to link users in a specific geographic area, such as within a city or county Sometimes government organizations or civic groups establish WANs to link users in a specific geographic area, such as within a city or county. This special type of WAN is known as a metropolitan area network (MAN). San Diego’s Traffic Management Center (TMC) uses a MAN to analyze traffic patterns. You can check out the traffic maps they generate at Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Personal Area Networks
A PAN is a network used to connect computing devices that are in close proximity to each other May feature wired or wireless connectivity PANs work within the personal operating space of an individual, generally defined to be within 30 feet of one’s body A personal area network (PAN) is a network used to connect computing devices that are in close proximity to each other. PANs may feature either wired or wireless connectivity. Bluetooth, a technology that uses radio waves to transmit data over short distances, is often used in wireless PANs (also known as WPANs). PANs work within the personal operating space of an individual, which is generally defined to be within 30 feet (or 10 meters) of one’s body. WPANs free you from having wires running to and from the devices you’re using. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Other Networks Intranet Extranet
Private network of business or organization Not accessible by unauthorized individuals Extranet An area of an intranet that only certain corporations or individuals can access Useful for enabling electronic data interchange An intranet is a private network set up by a business or an organization that is used exclusively by a select group of employees, customers, suppliers, volunteers, or supporters. It can facilitate information sharing, database access, group scheduling, videoconferencing, and other employee collaborations. Intranets are usually deployed using Transmission Control Protocol/Internet Protocol (TCP/IP), which is discussed in Chapter 13, and generally include links to the Internet. An intranet is not accessible by unauthorized individuals; a firewall protects it from unauthorized access through the Internet. An area of an intranet that only certain corporations or individuals can access is called an extranet. The owner of an extranet decides who will be permitted to access it. For example, a company’s customers and suppliers may be permitted to access information on the company’s extranet. Extranets are useful for enabling electronic data interchange (EDI), which allows the exchange of large amounts of business data (such as orders for merchandise) in a standardized electronic format. Walmart has an extranet that allows their employees, vendors, and contractors to easily share information. Other uses of extranets include providing access to catalogs and inventory databases and sharing information among partners or industry trade groups. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Servers Workhorses of the client/server network
Interface with many network users Assist with a variety of task Small networks have just one server Large networks use dedicated servers Fulfill one specific functions Reduce load on main server Servers are the workhorses of the client/server network. They interface with many different network users and assist them with a variety of tasks. The number and types of servers on a client/server network depend on the network’s size and workload. Small networks would have just one server to handle all server functions. A dedicated server is a server used to fulfill one specific function, such as handling . When more users are added to a network, dedicated servers are also added to reduce the load on the main server. Once dedicated servers are deployed, the original server can become merely an authentication server or a file server. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Print Servers Manage client-requested printing jobs for all printers on a network Helps client computers complete more productive work Frees the CPU to do other jobs Organize print jobs into orderly sequence Can prioritize print jobs Printing is a function that takes a large quantity of CPU time and that most people do quite often. Print servers manage all client-requested printing jobs for all printers on a network, which helps client computers to complete more productive work by relieving them of printing duties. When you tell your computer to print a document, it passes off the task to the print server. This frees the CPU on your computer to do other jobs. A print queue is a software holding area for print jobs. When the print server receives a job (a printing request) from a client computer, it puts the job into a print queue on the print server. Normally, each printer on a network has its own uniquely named print queue. Jobs receive a number when they enter the queue and go to the printer in the order in which they were received. Print queues thus function like the “take a number” machines at a supermarket deli. Thus, print servers organize print jobs into an orderly sequence to make printing more efficient on a shared printer. Another useful aspect of print servers is that network administrators can set them to prioritize print jobs. Different users and types of print jobs can be assigned different priorities so higher priority jobs will be printed first. For instance, in a company in which documents are printed on demand for clients, you would want these print jobs to take precedence over routine employee correspondence. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Application Servers Act as a repository for application software
Avoids installing software on thousands of personal computers Eases task of installation and upgrading Application is installed and upgraded only on the application server In many networks, all users run the same application software (such as Microsoft Office) on their computers. In a network of thousands of personal computers, installing application software on each computer is time consuming. An application server acts as a repository for application software. When a client computer connects to the network and requests an application, the application server delivers the software to the client computer. Because the software does not reside on the client computer itself, this eases the task of installation and upgrading. The application needs to be installed or upgraded only on the application server, not on each network client. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Database Servers Provides client computers with access to database information Many people can access a database at the same time through the network As its name implies, a database server provides client computers with access to information stored in databases. Often, many people need to access a database at the same time. For example, multiple college advisers can serve students at the same time because the advisers all have access to the student information database. This is made possible because the database resides on a database server that each adviser’s computer can access through the network. If the database were on a stand-alone computer instead of a network, only one adviser could use it at a time, making the process of serving students terribly inefficient. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Servers Volume of on large network could overwhelm a server Sole function of an server is to process and deliver Incoming Outgoing The volume of on a large network could quickly overwhelm a server that was attempting to handle other functions as well. The sole function of an server is to process and deliver incoming and outgoing . On a network with an server, when you send an from your computer, it goes to the server, which then handles the routing and delivery of your message. The server functions much like a postal carrier, who picks up your mail and sees that it finds its way towards the correct destination. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Communications Servers
Handles all communications between the network and other networks, including managing Internet connectivity Often the only device on the network directly connected to the Internet servers, Web servers, and other devices route traffic through the communications server A communications server handles all communications between the network and other networks, including managing Internet connectivity. All requests for information from the Internet and all messages being sent through the Internet pass through the communications server. Because Internet traffic is substantial at most organizations, the communications server has a heavy workload. The communications server often is the only device on the network connected to the Internet. servers, Web servers, and other devices needing to communicate with the Internet usually route all their traffic through the communications server. Providing a single point of contact with the outside world makes it easier to secure the network from hackers. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Web Servers & Cloud Servers
Host a Web site that will be available on the Internet Many colleges and businesses use a third-party Web hosting company Cloud servers Servers that are maintained by hosting companies, and are connected to networks via the Internet A Web server is used to host a Web site so it will be available through the Internet. Web servers run specialized software such as Apache HTTP Server (open source server software) and Microsoft Internet Information Services (IIS) that enable them to host Web pages. Not every large network has a Web server. Many colleges and businesses use a third-party Web hosting company to host their Web sites instead. Servers no longer need to be physically located at a company’s offices. Cloud servers are servers that are maintained by hosting companies, such as Rackspace Hosting, and that are connected to networks via the Internet. A company could choose to have any of the different types of servers discussed above hosted on cloud servers instead of maintaining them locally. Small businesses that don’t have a large staff of computer professionals often choose to use cloud servers to save money. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Network Topologies Arrangement of computers, transmission media, and other network components Physical topology Layout of “real” components of network Logical topology Virtual connections among network nodes Protocol is set of rules for exchanging communication Network topology refers to the physical or logical arrangement of computers, transmission media (cable), and other network components. Physical topology refers to the layout of the “real” components of the network, whereas logical topology refers to the virtual connections among network nodes. Logical topologies usually are determined by network protocols instead of the physical layout of the network or the paths electrical signals follow on the network. A protocol is a set of rules for exchanging communication. Although many people think that Ethernet is a type of network topology, it is actually a communications protocol. Therefore, an Ethernet network could be set up using almost any type of physical topology. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Bus Topology All computers are connected in sequence on a single cable
Used in peer-to-peer networks In a bus (or linear bus) topology, all computers are connected in sequence on a single cable.This topology was deployed most often in peer-to-peer networks (not client/server networks). It has largely become legacy technology due to the decreased cost of Ethernet networks (which use a star topology) and because a bus topology is not designed to easily support wireless connections. However, bus topologies are still found in some manufacturing facilities when connecting groups of computer-controlled machines. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Bus Topology Comparison
Advantages Disadvantages It uses a minimal amount of cable Installation is easy, reliable, and inexpensive Breaks in the cable can disable the network Large numbers of users will greatly decrease performance because of high volume of data traffic Advantages and disadvantages of bus topology: The simplicity and low cost of bus network topology were the major reasons it was deployed most often in P2P networks. The major disadvantage is that if there is a break in the cable, the bus network is effectively disrupted because some computers are cut off from others on the network. Only one computer can communicate at a time, so adding a large number of nodes to a bus network limits performance and causes delays in sending data. Because Ethernet networks don’t suffer from these limitations, you rarely see bus topologies today. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Ring Topology Nodes are laid out in a ring
A token (data packet) flows in one direction from device to device Recent versions have data transfer rates of up to 100 Mbps Not surprisingly, given its name, the computers and peripherals in a ring (or loop) topology are laid out in a configuration resembling a circle. Data flows around the circle from device to device in one direction only. Because data is passed using a special data packet called a token, this type of topology was once commonly called a token-ring topology. The original token-ring networks could achieve a data transfer rate (bandwidth) of either 4 Mbps or 16 Mbps, but more recent token technologies can deliver speeds as high as 100 Mbps. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Ring Topology Comparison
Advantages Disadvantages Allocates access to the network fairly Performance remains acceptable even with large numbers of users Adding or removing nodes disables network Failure of one computer can bring down the entire network Problems in the ring can sometimes be difficult to find Advantages and disadvantages of ring topology: A ring topology provides a fairer allocation of network resources than does a bus topology. By using a token, a ring network enables all nodes on the network to have an equal chance to send data. One “chatty” node cannot monopolize the network bandwidth as easily as in a bus topology because it must pass the token on after sending a batch of data. In addition, a ring topology’s performance will remain acceptable even with large numbers of users. One disadvantage of a ring network is that if one computer fails, it can bring the entire network to a halt because that computer is unavailable to retransmit tokens and data. Another disadvantage is that problems in the ring can be hard for network administrators to find. It’s easier to expand a ring topology than a bus topology, but adding a node to a ring does cause the ring to cease to function while the node is being installed. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Star Topology Most widely deployed client/server network layout
Nodes connect to a central communications device (switch) Switch receives a signal and retransmits it A node accepts only signals addressed to it A star topology is the most widely deployed client/server network layout today because it offers the most flexibility for a low price. In a star topology, the nodes connect to a central communications device called a switch in a pattern resembling a star. The switch receives a signal from the sending node and retransmits it to the node on the network that needs to receive the signal. Each network node picks up only the transmissions addressed to it. Because the switch retransmits data signals, a star topology is an active topology. The only drawback is that if the switch fails, the network no longer functions. However, it is relatively easy to replace a switch. Many star networks use the Ethernet protocol. Networks using the Ethernet protocol are by far the most common type of network in use today. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Star Topology Comparison
Advantages Disadvantages Failure of one computer does not affect other computers on the network Centralized design simplifies troubleshooting and repairs Adding computers or groups of computers is easy. Performance remains acceptable even with large numbers of users Requires more cable (and possibly higher installation costs) than a bus or ring topology The switch is a single point of failure If it fails, all computers connected to that switch are affected Advantages and disadvantages of star topology: The main reason a star topology generally is considered to be superior to a ring topology is that if one computer on a star topology fails, it doesn’t affect the rest of the network. This is extremely important in a large network in which having one disabled computer affect the operations of several hundred other computers would be unacceptable. Another advantage is that it is easy to add nodes to star networks. Furthermore, performance remains acceptable even with large numbers of users. In addition, centralizing communications through a switch makes troubleshooting and repairs on star networks easier for network technicians. Technicians can usually pinpoint a communications problem just by examining the switch, as opposed to searching for a particular length of cable that broke in a ring network. The disadvantage of star networks used to be cost. Because of the complexity of the layout of star networks, they require more cable and used to be more expensive than bus or ring networks. Because the price of cable has fallen and wireless nodes are replacing many wired nodes on networks, this has ceased to be a barrier in most cases. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Transmission Media Network engineers can use different type of media
Transmission media comprise the physical system that data takes to flow between devices on a network Wired connections Wireless connections A variety of building materials are available for constructing a house; the ones chosen will depend on the needs of the builder. Similarly, when building a network, network engineers can use different types of media. Transmission media, whether for wired or wireless communications technology, comprise the physical system that data takes to flow between devices on the network. Without transmission media, network devices would be unable to communicate. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Wired Transmission Media
Popular in business networks Generally provide higher throughput than wireless connections Types of wired connections Twisted-pair cable Coaxial cable Fiber-optic cable Wired connections are popular in business networks because they generally provide higher throughput than wireless connections. Desktop computers still provide more computing power for less money than notebooks, which makes desktop computers popular choices for business networks. Because desktops aren’t often moved around, they are usually connected to a network with a wired connection. Twisted-pair cable should be familiar to you because the telephone cable (or wire) in your home is one type of twisted-pair cable. Twisted-pair cable consists of pairs of copper wires twisted around each other and covered by a protective sheath (jacket). The twists are important because they cause the magnetic fields that form around the copper wires to intermingle, which makes them less susceptible to outside interference. The twists also reduce the amount of crosstalk interference (the tendency of signals on one wire to interfere with signals on a wire next to it). Coaxial cable should be familiar to you if you have cable television, because most cable television installers use coaxial cable. Coaxial cable consists of four main components: 1. The core (usually copper) is in the very center and is used for transmitting the signal. 2. A solid layer of nonconductive insulating material (usually a hard, thick plastic) surrounds the core. 3. A layer of braided metal shielding covers the insulation to reduce interference with signals traveling in the core. 4. An external jacket of lightweight plastic covers the internal cable components to protect them from damage. The core of fiber-optic cable is composed of a glass (or plastic) fiber (or a bundle of fibers) through which the data is transmitted. A protective layer of glass or plastic cladding is wrapped around the core to protect it. Finally, for additional protection, an outer jacket (sheath) is added, often made of a durable material such as Kevlar (the substance used to make bulletproof vests). Data transmissions can pass through fiber-optic cable in only one direction. Therefore, at least two cores are located in most fiber-optic cables to enable transmission of data in both directions. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Choosing a Cable Maximum run length Bandwidth
Bend radius (flexibility) Cable and installation costs Susceptibility to interference Signal transmission methods Although each cable type is different, the same criteria always need to be considered when choosing a cable type: Maximum run length: Each type of cable has a maximum run length over which signals sent across it can be “heard” by devices connected to it. Therefore, when designing a network, network engineers must accurately measure the distances between devices to ensure that they select an appropriate cable. Bandwidth: As you learned in earlier chapters, bandwidth is the amount of data that can be transmitted across a transmission medium in a certain amount of time. Each cable is different and is rated by the maximum bandwidth it can support. Bandwidth is measured in bits per second, which represents how many bits of data can be transmitted along the cable each second. Bend radius (flexibility): When installing cable, it is often necessary to bend the cable around corners. The bend radius of the cable defines how many degrees a cable can be bent in a one-foot segment before it is damaged. If many corners need to be navigated when installing a network, network engineers use cabling with a high bend radius. Cable cost: The cost per foot of different types and grades of cable varies widely. Cable selection may have to be made based on cost if adequate funds are not available for the optimal type of cabling. Installation costs: Twisted pair and coaxial cable are easy and inexpensive to install. Fiber-optic cable requires special training and equipment to install, which increases the installation costs. Susceptibility to interference: Signals traveling down a cable are subject to two types of interference. Electromagnetic interference (EMI), which is caused when the cable is exposed to strong electromagnetic fields, can distort or degrade signals on the cable. Fluorescent lights and machinery with motors or transformers are the most common sources of EMI emissions. Cable signals also can be disrupted by radio frequency interference (RFI), which is usually caused by broadcast sources (television and radio signals) located near the network. Cable types are rated as to how well they resist interference. Signal transmission methods: Both coaxial cable and twisted-pair cable send electrical impulses down conductive material to transmit data signals. Fiber-optic cable transmits data signals as pulses of light. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Twisted-Pair Cable Pairs of copper wire twisted around each other
Twists make the wires less susceptible to outside interference Two types Shielded twisted-pair (STP) Unshielded twisted-pair (UTP Twisted-pair cable should be familiar to you because the telephone cable (or wire) in your home is one type of twisted-pair cable. Twisted-pair cable consists of pairs of copper wires twisted around each other and covered by a protective sheath (jacket). The twists are important because they cause the magnetic fields that form around the copper wires to intermingle, which makes them less susceptible to outside interference. The twists also reduce the amount of crosstalk interference (the tendency of signals on one wire to interfere with signals on a wire next to it). If the twisted-pair cable contains a layer of foil shielding to reduce interference, it is known as shielded twisted-pair (STP) cable. If it does not contain a layer of foil shielding, it is known as unshielded twisted-pair (UTP) cable. This type is more susceptible to interference. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Coaxial Cable Four main components Copper core
Nonconductive insulating material Braided metal shielding Plastic cover Coaxial cable should be familiar to you if you have cable television, because most cable television installers use coaxial cable. Coaxial cable consists of four main components: 1. The core (usually copper) is in the very center and is used for transmitting the signal. 2. A solid layer of nonconductive insulating material (usually a hard, thick plastic) surrounds the core. 3. A layer of braided metal shielding covers the insulation to reduce interference with signals traveling in the core. 4. An external jacket of lightweight plastic covers the internal cable components to protect them from damage. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Fiber-Optic Cable Components include
Glass or plastic fibers Cladding Outer jacket Transmission in only one direction Signals converted to light pulses Immune to interference The core of fiber-optic cable is composed of a glass (or plastic) fiber (or a bundle of fibers) through which the data is transmitted. A protective layer of glass or plastic cladding is wrapped around the core to protect it. Finally, for additional protection, an outer jacket (sheath) is added, often made of a durable material such as Kevlar (the substance used to make bulletproof vests). Data transmissions can pass through fiber-optic cable in only one direction. Therefore, at least two cores are located in most fiber-optic cables to enable transmission of data in both directions. In a fiber-optic cable, electrical data signals from network devices (client computers, peripherals, and so on) are converted to light pulses before they are transmitted. Because EMI and RFI do not affect light waves, fiber-optic cable is virtually immune to interference. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Wireless Media Options
Usually add-ons that extend access to wired network Often provided to give employees a wider working area Corporate networks are often a combination of wired and wireless media Although the word wireless implies “no wires,” in businesses, wireless media are usually add-ons that extend or improve access to a wired network. In the corporate environment, wireless access is often provided to give employees a wider working area. For instance, if conference rooms offer wireless access, employees can bring their notebooks to meetings and gain access to the network during the meeting. However, when they go back to their offices, they may connect to the network through a wired connection. Accordingly, corporate networks are often a combination of wired and wireless media. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Comparing Transmission Media
Cable Characteristics Twisted Pair (Cat 6) Twisted Pair (Cat 6a) Fiber-Optic Maximum run length 328 feet (100 m) Up to 62 miles (100 km) Bandwidth Up to 1 Gbps Up to 10 Gbps 10 to 40 Gbps Bend radius (flexibility) No limit 30 degrees/foot Cable cost Extremely low Low High Installation cost Most expensive because of installation training required Susceptibility to interference None (not susceptible to EMI or RFI) Comparison of transmission media. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Network Operating Systems
Special NOS software must be installed on each client computer and server NOS provides a set of common rules that controls communication among devices Modern operating systems include NOS client software Merely using media to connect computers and peripherals does not create a client/server network. Special software known as a network operating system (NOS) needs to be installed on each client computer and server connected to the network to provide the services necessary for them to communicate. The NOS provides a set of common rules (a protocol) that controls communication among devices on the network. Modern operating systems, such as Windows 7 and Mac OS X, include NOS client software as part of the basic installation. However, the operating systems sold with stand-alone computers do not include the NOS server software needed to run a large network. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Network Adapters Devices that perform tasks to enable computers to communicate on a network Network interface cards (NICs) are installed inside computers and peripherals Network adapters perform three critical functions: Generate network transmission signals Create data packets Act as information gatekeepers Network adapters are devices that perform specific tasks to enable computers to communicate on a network. Network adapters are installed inside computers and peripherals. These adapters are referred to as network interface cards (NiCs). Network adapters perform three critical functions: 1. They generate high-powered signals to enable network transmissions. Digital signals generated inside the computer are fairly low powered and would not travel well on cable or wireless network media without network adapters. Network adapters convert the signals from inside the computer to higher-powered signals that have no trouble traversing the network media. 2. They are responsible for breaking the data into packets and preparing the packets for transmission across the network. They also are responsible for receiving incoming data packets and, in accordance with networking protocols, reconstructing them. NIC is responsible for breaking down data into packets, preparing packets for transmission, receiving incoming data packets, and reconstructing them. 3. They act as gatekeepers for information flowing to and from the client computer. Much like a security guard in a gated community, a network adapter is responsible for permitting or denying access to the client computer (the community) and controlling the flow of data (visitors). Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Network Navigation Devices
Data flows through network in packets Each network adapter has physical address called a media access control (MAC) address Six two-position characters (such as 01:40:87:44:79:A5) First three sets specify manufacturer Second set makes up unique address Data flows through the network in packets. Data packets are like postal letters. They don’t get to their destinations without some help. In this section, we explore the various conventions and devices that help speed data packets on their way through the network. Each network adapter has a physical address similar to a serial number on an appliance. This is called a media access control (MAC) address, and it is made up of six two-position characters such as 01:40:87:44:79:A5. (Don’t confuse this MAC with the Apple computers of the same name.) The first three sets of characters (in this case, 01:40:87) specify the manufacturer of the network adapter, whereas the second set of characters (in this case, 44:79:A5) makes up a unique address. Because all MAC addresses must be unique, there is an IEEE committee responsible for allocating blocks of numbers to network adapter manufacturers. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Switches and Bridges Used to send data on a specific route through network Switch makes decisions based on MAC address as to where data is sent Bridge is a device used to send data between different collision domains Switches and bridges are used to send data on a specific route through the network. A switch makes decisions, based on the MAC address of the data, as to where the data is to be sent and directs it to the appropriate network node. This improves network efficiency by helping to ensure that each node receives only the data intended for it. Switches are needed on Ethernet networks whether installed in the home or a business. Routers sold for home use have switches built into them. When a corporate network grows in size, performance can decline because many devices compete for transmission time on the network media. To solve this problem, a network can be broken into multiple segments known as collision domains. A bridge is a device that is used to send data between these different collision domains. A bridge sends data between collision domains, depending on where the recipient device is located. Signals received by the bridge from collision domain A are forwarded to collision domain B only if the destination computer is located in that domain. Most home networks contain only one segment and therefore do not require bridges. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Routers Router is designed to send information between two networks
Must look at higher-level network addresses such as IP addresses Whereas switches and bridges perform their functions within a single network, a router is designed to send information between two networks. To accomplish this, the router must look at higher-level network addresses (such as IP addresses), not MAC addresses. When the router notices data with an address that does not belong to a device on the network from which it originated, it sends the data to another network to which it is attached or out onto the Internet. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Network Security for Client/Server Networks
Offer higher level of security than peer-to-peer networks Security can be centrally administered by network administrators Frees individual users of responsibility of maintaining own data security A major advantage that client/server networks have over peer-to-peer networks is that they offer a higher level of security. With client/server networks, users can be required to enter a user ID and a password to gain access to the network. The security can be centrally administered by network administrators, freeing individual users of the responsibility of maintaining their own data security, as they must do on a peer-to-peer network. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Sources of Security Threats
Human errors and mistakes Incorrect posting Malicious human activity Perpetrated by current/former employees or third parties Natural events and disasters Hurricanes and other acts of nature Threats can be classified into three main groups: human errors and mistakes, malicious human activity, and natural events and disasters. Human errors and mistakes: Everyone makes mistakes. For example, the clerk processing your tuition payment could accidentally post it to another student’s account. A member of the computer support staff could mistakenly install an old database on top of the current one. Even physical accidents fall into this category; for example, someone could lose control of a car and drive it through the wall of the main data center. Malicious human activity: Malicious actions can be perpetrated by current employees, former employees, or third parties. For example, a disgruntled employee could introduce a virus to the network. Or a hacker could break into the student database server to steal credit card records. Natural events and disasters: Some events—such as broken water pipes, or disasters such as hurricanes and other acts of nature—are beyond human control. All can lead to the inadvertent destruction of data. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Network Security for Client/Server Networks
Offer higher level of security that can be centrally administered Threats can be classified into three groups: Human errors and mistakes Malicious human activity Natural events and disasters A major advantage that client/server networks have over peer-to-peer networks is that they offer a higher level of security. The security can be centrally administered by network administrators, freeing individual users of the responsibility of maintaining their own data security, as they must do on a peer-to-peer network. Threats can be classified into three main groups: human errors and mistakes, malicious human activity, and natural events and disasters. Human errors and mistakes: Everyone makes mistakes. For example, the clerk processing your tuition payment could accidentally post it to another student’s account. A member of the computer support staff could mistakenly install an old database on top of the current one. Even physical accidents fall into this category; for example, someone could lose control of a car and drive it through the wall of the main data center. Malicious human activity: Malicious actions can be perpetrated by current employees, former employees, or third parties. For example, a disgruntled employee could introduce a virus to the network. Or a hacker could break into the student database server to steal credit card records. Natural events and disasters: Some events—such as broken water pipes, or disasters such as hurricanes and other acts of nature—are beyond human control. All can lead to the inadvertent destruction of data. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Authentication Process where users prove they have authorization to use computer network Provide a user ID and password Biometric devices Possessed objects Identification badges Magnetic key cards Smart keys Authentication is the process whereby users prove they have authorization to use a computer network. The type of authentication most people are familiar with consists of providing a user ID and password. For example, correctly entering the user ID and password on your college network proves to the network that you have authorized access. The access is authorized because the ID was generated by a network administrator when you became an authorized user of the network. However, authentication can also be achieved through the use of biometric devices and through possessed objects. A possessed object is any object that a user carries to identify himself and that grants him access to a computer system or computer facility. Examples include identification badges, magnetic key cards, and smart keys (similar to flash drives). Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Access Privileges When account is set up, certain access privileges are granted to indicate which systems you are allowed to use On a college network you might: Have ability to access the Internet View grades and transcripts Would not have ability to change grades When your account is set up on a network, certain access privileges are granted to indicate which systems you are allowed to use. For example, on your college network, your access privileges probably include the ability to access the Internet. You also might have access privileges to view your transcript and grades online. However, you definitely were not granted access to the grade reporting system, because this would enable you to change your grades. Likewise, you did not receive access to the financial systems; otherwise, you might be able to change your account, indicating that your bill was paid when it had not been. Because network access accounts are centrally administered on the authentication server, it is easy for the network administrator to set up accounts for new users and grant them access only to the systems and software they need. The centralized nature of the creation of access accounts and the ability to restrict access to certain areas of the client/server network make it more secure than a peer-to-peer network. If you shouldn’t go somewhere (such as into the files that record student grades), you can’t get there on your school network! Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Physical Protection Measures
Restricting physical access to servers and other equipment is critical Devices are secured in ceilings, walls, or closets Only authorized personnel have access Restricting physical access to servers and other sensitive equipment is critical to protecting a network. Where are the servers that power your college network? They are most likely behind locked doors to which only authorized personnel have access. Do you see any routers or switches lying about in computer labs? Of course you don’t. These devices are securely tucked away in ceilings, walls, or closets, safe from anyone who might tamper with them in an attempt to sabotage the network or breach its security. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Firewalls Firewalls for business networks work on same principles as personal firewall Work as packet screeners with external screening router examining incoming data packets Unauthorized or suspect packets are discarded A well-defended business network, just like a well-defended home network, includes a firewall. Firewalls can be composed of software or hardware, and many sophisticated firewalls include both. Routers are often equipped to act as hardware firewalls. Just like a home network, any company’s network that is connected to the Internet can create an attractive nuisance and attract hackers. Although a firewall on a business network may contain a few extra security options, making it even harder to breach than a personal firewall, the firewalls for business networks work on the same basic principles as a personal firewall. At a minimum, most firewalls work as packet screeners. Packet screening involves having an external screening router examining incoming data packets to ensure that they originated from or are authorized by valid users on the internal network. Unauthorized or suspect packets are discarded by the firewall before they reach the network. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Network Firewall Layout
This illustration shows the multiple levels of protection that the internal networked computer has from external Internet threats. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Chapter 12 Summary Questions
What are the advantages of a business network? 1. What are the advantages of a business network? A network enables employees to communicate with each other more easily, even over large distances. Networks also enable resources, such as printers, to be shared, avoiding the cost of providing these resources to individual employees. Software can be deployed from a network server, thereby reducing the costs of installation on each user’s computer. Finally, networks enable employees to share an Internet connection, avoiding the cost of providing each employee with a dedicated Internet connection. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

How does a client/server network differ from a peer-to-peer network? How does a client/server network differ from a peer-to-peer network? A client/server network requires at least one server to be attached to the network. The server coordinates functions such as file sharing and printing. In a peer-to-peer network, each node connected to the network can communicate directly with every other node on the network. In a client/server network, a separate device (the server) exercises control over the network. Data flows more efficiently in client/server networks than in peer-to-peer networks. In addition, client/server networks have increased scalability, meaning users can be added to the network easily. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

What are the different classifications of client/server networks? What are the different classifications of client/server networks? Local area networks (LANs) are small groups of computers (as few as two) and peripherals linked together over a small geographic area. A group of computers in rooms on one floor of a campus building is most likely a LAN. Wide area networks (WANs) comprise large numbers of users (or of separate LANs) that are miles apart and linked together. Colleges often use WANs to connect two or more campuses in separate towns.. Sometimes government organizations or civic groups establish WANs to link users in a specific geographic area (such as within a city or county). These special WANs are known as metropolitan area networks (MANs). Personal area networks (PANs) are networks that connect personal use devices, such as phones and tablets, that are usually carried on your person. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

What components are needed to construct a client/server network? 4. What components are needed to construct a client/server network? Client/server networks have many of the same components as peer-to-peer networks as well as some components specific to client/server networks, including servers, a network topology, transmission media, network operating system (NOS) software, network adapters, and network navigation devices. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

What do the various types of servers do? 5. What do the various types of servers do? Dedicated servers are used on large networks to increase efficiency. Authentication servers control access to the network and ensure that only authorized users can log on. File servers provide storage and management of user files. Print servers manage and control all printing jobs initiated on a network. Application servers provide access to application software (such as Microsoft Office). Database servers store database files and provide access to users who need the information in the databases. servers control all incoming and outgoing traffic. Communications servers are used to control the flow of information from the internal network to outside networks (such as the Internet). Web servers are used to host Web sites. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

What are the various network topologies (layouts), and why is network topology important in planning a network? 6. What are the various network topologies (layouts), and why is network topology important in planning a network? In a bus topology, all nodes are connected to a single linear cable. Ring topologies are made up of nodes arranged roughly in a circle. The data flows from node to node in a specific order. In a star topology, nodes are connected to a central communication device (a switch) and branch out like points of a star. A hybrid topology blends two or more topologies in one network. Each topology has its own advantages and disadvantages. Topology selection depends on two main factors: (1) the network budget, and (2) the specific needs of network users (such as speed or fair allocation of resources). Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

What types of transmission media are used in client/server networks? 7. What types of transmission media are used in client/server networks? In addition to wireless media, three main cable types are used: twisted-pair cable, coaxial cable, and fiber-optic cable. Twisted-pair cable consists of four pairs of wires twisted around each other to reduce interference. Coaxial cable is the same type of cable used by your cable TV company to run a signal into your house. Fiber-optic cable uses bundles of glass or plastic fiber to send signals using light waves. It provides the largest bandwidth but is expensive and difficult to install. Wireless media uses radio waves to send data between nodes on a network. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

What software needs to run on computers attached to a client/server network, and how does this software control network communications? 8. What software needs to run on computers attached to a client/server network, and how does this software control network communications? Network operating system (NOS) software needs to be installed on each computer and server connected to a client/server network to provide the services necessary for the devices to communicate. The NOS provides a set of common rules (called a protocol) that controls communication between devices on the network. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

How do network adapters enable computers to participate in a client/server network? 9. How do network adapters enable computers to participate in a client/server network? Without a network adapter, a computer could not communicate on a network. A network adapter provides three critical functions. First, it takes low-power data signals generated by the computer and converts them into higher-powered signals that can traverse network media easily. Second, it breaks the data generated by the computer into packets and packages them for transmission across the network media. Last, it acts as a gatekeeper to control the flow of data to and from the computer. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

What devices assist in moving data around a client/server network? 10. What devices assist in moving data around a client/server network? Switches are devices that read the addresses of data packets and retransmit a signal to its destination instead of to every device connected to the switch. Bridges are devices used to send data between two different segments (collision domains) of the same network. Routers are used to route data between two different networks (such as between a college network and the Internet). Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

What measures are employed to keep large networks secure? 11. What measures are employed to keep large networks secure? Access to most networks requires authentication procedures (such as having users enter a user ID and password) to ensure that only authorized users access the network. The system administrator defines access privileges for users so that they can access only specific files. Network equipment is physically secured behind locked doors, which are often protected by biometric authentication devices. Biometric devices, such as fingerprint and palm readers, use unique physical characteristics of individuals for identification purposes. Firewalls are employed to keep hackers from attacking networks through Internet connections. Packet screeners review traffic going to and from the network to ascertain whether the communication was generated by a legitimate user. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America. Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

Technology in Action Chapter 12 Behind the Scenes: Networking and Security in the Business World This chapter takes you behind the scenes of networking.

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Technology in Action Chapter 12 Behind the Scenes: Networking and Security in the Business World This chapter takes you behind the scenes of networking.

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