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

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 © Pearson Education, Inc. Publishing as Prentice Hall

Chapter Topics Advantages of business networks
Client/server vs. peer-to-peer networks Classifications of client/server networks Client/server network components Types of servers Network topologies Chapter topics include: Advantages of business networks Client/server vs. peer-to-peer networks Classifications of client/server networks Client/server network components Types of servers Network topologies Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Chapter Topics (cont.) Types of transmission media Network software
Network adapters Moving data in a client/server network Securing networks Types of transmission media Network software Network adapters Moving data in a client/server network Securing networks Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Networking Advantages
Networks Increase productivity Enable the sharing of hardware resources Facilitate knowledge sharing Enable the sharing of software 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. Home networks enable users to share an Internet connection, peripherals, and media. Large business networks provide the following advantages: Increase productivity by allowing workers to share data and peripherals with coworkers and to communicate with them efficiently. Enable people to share peripherals such as printers. Enable knowledge sharing. They can serve the needs of many people at one time and increase the availability of data. Enable software sharing. If computers are networked, all employees can access the same copy of a program from the server. Although companies must still purchase a software license for each employee, with a network they avoid having to install the program on every desktop. Facilitate Internet connectivity. Through a network, large groups of employees can share one Internet connection, reducing Internet connectivity expenses. Enable enhanced communication. and text messaging are extremely powerful applications when deployed on a network. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Networking Disadvantages
Networks Complex Additional personnel required to maintain them Require special equipment and software Business networks are often complex and usually require additional personnel 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. Operating a network requires special equipment and software. However, most companies feel the cost savings of peripheral sharing and the ability to give employees simultaneous access to information outweigh the costs associated with network administrators. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Client/Server Networks
Data flows efficiently Servers respond to requests from clients Servers perform specific tasks Scalable Centralized 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 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. Also, servers are configured to perform specific tasks (such as handling database requests) efficiently. Client/server networks are scalable, meaning that additional users can be added easily without affecting the performance of the other network nodes. Client/server networks are centralized, meaning that all clients connect to a server that performs tasks for them. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Classifications of Client/Server Networks
LAN Local area network Computers linked over a small geographic area Local area networks (LANs) are generally small groups of computers and peripherals linked together over a relatively small geographic area. The computer lab at your school or the network on the floor of the office where you work is probably a LAN. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Classifications of Client/Server Networks (cont.)
WAN Wide area network Computers linked over large geographic areas MAN Metropolitan area network Computers linked within a city or county Wide area networks (WANs) include large numbers of users over a wider physical area or separate LANs that are miles apart. Corporations often use WANs to connect two or more geographically diverse branches. 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). Copyright © Pearson Education, Inc. Publishing as Prentice Hall

PAN Personal area network Wireless devices connected in close proximity to each other Intranet Private corporate network Protected from the Internet by a firewall Personal area networks (PANs) are used to connect wireless devices (such as Bluetooth-enabled devices) in close proximity to each other. PANs are wireless and operate in the personal operating space of an individual, which is generally defined to be within 30 feet of one’s body. An intranet is a private network set up by an entity (such as a business, charity, or government organization) that is used exclusively by a select group of individuals to facilitate information sharing, database access, group scheduling, videoconferencing, or other employee collaboration. The intranet is not accessible to unauthorized individuals; a firewall protects it from unauthorized access through the Internet. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Extranets Only certain corporations or individuals can access Useful for enabling electronic data interchange Use virtual private networks for security Extranets are areas of intranets that only certain corporations or individuals can access. The owner of the extranet decides who will be permitted to access it. Customers and suppliers are typical entities that would benefit from accessing information on an extranet. Extranets are useful for enabling electronic data interchange (EDI). Other uses of extranets include providing access to catalogs and inventory databases and sharing information among partners or industry trade groups. Because of security concerns, intranets and extranets often use virtual private networks to keep information secure. A virtual private network (VPN) uses the public Internet communications infrastructure to build a secure, private network between various locations. VPNs use special security technologies and protocols that enhance security, enabling data to traverse the Internet as securely as if it were on a private leased line. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Constructing Client/Server Networks
Servers Network topologies Transmission media Network operating system software Network adapters Network navigation devices Client/server networks share many of the same components of P2P networks as well as some components specific to client/server networks. Server: Unlike P2P networks, client/server networks contain at least one computer that functions solely as a server. Network topology: Because client/server networks are more complex than P2P networks, the layout and structure of the network must be carefully planned. Transmission media: An appropriate type of transmission media (cable or wireless communications technology) is needed based on the network topology. All client/server networks require network operating system (NOS) software. Network adapters: All nodes on the network must contain adapters (network interface cards). These adapters enable a computer (or peripheral) to communicate with the network using a common data communication language, or protocol. Because of the complexity of a client/server network, specialized network navigation devices (such as routers) are needed to move data signals around the network. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Servers The number and types of servers depend on network size and workload Dedicated servers Perform one specific function Authentication servers Keep track of network logins and services available File servers Store and manage files Servers support many different network users and assist them with accomplishing a variety of tasks. The number and types of servers on a client/server network depend on the network’s size and workload. Dedicated servers are used to fulfill one specific function, such as handling . When dedicated servers are deployed, the original server can become merely an authentication server or a file server. Authentication servers keep track of who is logging on to the network and which services on the network are available to each user. Authentication servers also act as overseers for the network. They manage and coordinate the services provided by any other dedicated servers located on the network. File servers store and manage files for network users. In corporate networks, employees are provided with space on a file server to store the files they create. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Servers (cont.) Print servers Application servers Database servers
Manage client-requested printing jobs Create a print queue (prioritize print jobs) Application servers Act as a storage area for application software Database servers Provide clients with access to database information servers Process and deliver incoming and outgoing A network with a centralized printing service has a print server that manages 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. Application servers act as a repository for application software such as Microsoft Office. When a client computer connects to the network and requests an application, the application server delivers the software to the client computer. The software does not reside on the client computer itself, which eases the task of installation and upgrading. Database servers are dedicated to an organization’s database storage, queries, and retrievals. servers have as their sole function processing and delivering incoming and outgoing . Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Servers (cont.) Communications servers Web servers
Handle communications between networks, including the Internet Often the only device on the network directly connected to the Internet Web servers Host a Web site available through the Internet 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. Often, the communications server 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. A Web server is used to host a Web site available through the Internet. Web servers run specialized software that enables them to host Web pages. Not every large network has a Web server; many use a third-party Web hosting company to host their Web sites instead. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Network Topologies The physical or logical layout of computers, transmission media, and other components Types of network topologies Bus Ring Star Hybrid 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 pertains to virtual connections between network nodes. Logical topologies usually are determined by network protocols rather than by the physical layout of the network or the paths electrical signals follow on the network. The most common client/server network topologies are ring and star. Bus is becoming a legacy topology. Combining multiple topologies into one network is known as constructing a hybrid topology. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Bus Topology All nodes are connected in sequence on a single cable
Networked computers communicate with each other One computer transmits data at a time Becoming obsolete A bus topology uses a single cable, or “bus,” to handle transmission of signals between computers. Each computer on a bus network can communicate with every other computer on the network directly. A limitation of bus networks is that data collisions can occur easily if two computers transmit data at the same time, because a bus network is essentially composed of one main communication medium (single cable). Bus topologies were most often used in P2P networks, but are becoming obsolete due to the decreased cost of Ethernet, which uses a star topology, and due to the fact that the bus topology is not designed to easily support wireless connections. Data collisions, which happen when two computers send data at the same time and the sets of data collide somewhere in the media, are a problem on all networks and can occur fairly easily on bus networks. When data collides it is often lost or irreparably damaged. Copyright © 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 The computers and peripherals in a ring (or loop) topology are laid out in a circle. Data flows around the circle from device to device in one direction only. Data is passed using a special data packet called a token. This type of topology is commonly referred to as a token-ring topology. Token-ring networks originally had data transfer rates (bandwidth) of either 4 Mbps or 16 Mbps. More recent token technologies can deliver speeds of up to 100 Mbps. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Star Topology Most widely deployed client/server layout
Nodes connect to a central communications device (switch) A node sends a signal to the switch, which retransmits it to the other nodes 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, forming the shape of a star. The switch receives a signal from the sending node and retransmits it to the nodes on the network that need to receive the signal. Each network node picks up only those transmissions addressed to it. Because the switch retransmits data signals, a star topology is an active topology. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Avoiding Data Collisions on an Ethernet Network
Because most star networks are Ethernet networks, they use the method used on all Ethernet networks to avoid data collisions: CSMA/CD (short for carrier sense multiple access with collision detection). With CSMA/CD, a node connected to the network listens (i.e., has carrier sense) to determine that no other nodes are currently transmitting data signals. If the node doesn’t hear any other signals, it assumes it is safe to transmit data. All devices on the network have the same right (i.e., they have multiple access) to transmit data when they deem it safe. It is therefore possible for two devices to begin transmitting data signals at the same time. If this happens, the two signals collide. When signals collide, a node on the network detects the collision. It then sends a special signal, called a jam signal, to all network nodes, alerting them that a collision has occurred. The nodes then stop transmitting and wait a random amount of time before retransmitting their data signals. The wait time needs to be random because otherwise both nodes would start transmitting at the same time and another collision would occur. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Comparing Topologies Topology Advantages Disadvantages Bus Ring Star
Uses a minimal amount of cabling. Breaks in the cable can disable the network. Easy, reliable, and inexpensive to install. Large numbers of users will greatly decrease performance because of high volumes of data traffic. Ring Allocates access to the network fairly. Adding or removing nodes disables the network. Performance remains acceptable even with large numbers of users. Failure of one computer can bring down the entire network. Problems in data transmission can sometimes be difficult to find. Star Failure of one computer does not affect other computers on the network. Requires more cable (and possibly higher installation costs) than a bus or ring topology. Centralized design simplifies troubleshooting and repairs. The switch is a central point of failure. If it fails, all computers connected to that switch are affected. Easy to add more computers or groups of computers as needed (high scalability). Star topologies are the most common mainly because large networks are constantly adding new users. The ability to add new users simply (that is, by installing a new switch) without affecting users already on the network is the deciding factor. Bus topologies have become all but extinct as home networks have moved to a star topology. Ring topologies are still popular in some businesses when fair allocation of network access is a major requirement of the network. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Transmission Media The routes data takes to flow between devices on a network Wired Twisted-pair Coaxial Fiber optic Wireless Transmission media comprise the routes data takes to flow between devices on a network. For business networks, the three main cable types used today are twisted-pair, coaxial, and fiber optic. Wireless networks are another popular option. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Choosing a Cable Maximum run length Bandwidth Bend radius
Cable and installation costs Susceptibility to interference Signal transmission methods Wired media are the typical transmission solution in large networks. The type of cable that’s best is determined by a series of factors, including the following: 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. Bandwidth: 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. Bend radius (flexibility): The bend radius of the cable defines how many degrees a cable can be bent in a 1-foot segment before it is damaged. Cable cost: The cost per foot of different types and grades of cable varies widely. Installation costs: Certain cable types (such as twisted-pair) are easy and inexpensive to install. Fiber-optic cable requires special training and equipment to install. Susceptibility to interference: Signals traveling down a cable are subject to interference. Cable types are rated as to how well they resist interference. Signal transmission methods: Coaxial cable and twisted-pair cable both send electrical impulses down conductive material to transmit data signals. Fiber-optic cable transmits data signals as pulses of light. Copyright © 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 consists of pairs of copper wire twisted around each other and covered by a protective jacket (or sheath). The twists cause the magnetic fields that form around the copper wires to intermingle, which makes them less susceptible to interference. 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 and is more susceptible to interference. There are different standard categories of UTP cable: Category 6 (Cat 6) can handle a bandwidth of 1 gigabit per second (Gbps). Category 6a (Cat 6a) can handle a bandwidth of 10 gigabits per second (Gbps). Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Coaxial Cable Four components Copper core
Nonconductive insulating material Braided metal Plastic cover Coaxial cable is the cable used with cable TV. It consists of four main components: A copper center core used for transmitting the signal A solid layer of nonconductive insulating material surrounding the core A layer of braided metal that reduces interference An external jacket of lightweight plastic that covers the internal cable components to protect them from damage Although coaxial cable used to be the most widely used type of cable in business networks, advances in twisted-pair cable shielding and transmission speeds, as well as twisted-pair’s lower cost, have reduced the popularity of coaxial cable. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Fiber-Optic Cable Components include
Glass or plastic fibers Cladding Outer jacket Uses light impulses to transmit data Immune to interference Fiber-optic cable is composed of a glass (or plastic) fiber (or bundle of fibers) that makes up the core of the cable where the data is transmitted. Cladding, a protective layer made of glass or plastic, is wrapped around the core to protect it. Finally, for additional protection, an outer jacket (sheath) is added. In a fiber-optic cable, electrical data signals from network devices are converted to light pulses before they are transmitted. Fiber-optic cable is virtually immune to interference. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Wireless Media 802.11 Standard
In business, wireless media are usually add-ons to a wired network Wi-Fi standard In business, wireless media are usually add-ons to extend or improve access to a wired network. Wireless networks in the United States are currently based on the standard, also known as Wi-Fi . Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Network Operating Systems (NOS)
Provide services necessary for client computer and server to communicate Many modern OSs include NOS client software Major network operating systems Windows Server 2008 R2 UNIX Linux Novell SUSE Linux Enterprise 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. Many modern operating systems (such as Windows 7 and Mac OS X) include NOS client software as part of the basic installation. If your OS does not include NOS client software, it must be installed on each client. The NOS provides a set of common rules (a protocol) that controls communication among devices on the network. The major NOSs on the market today include Windows Server 2008 R2, Linux, UNIX, and Novell SUSE Linux Enterprise. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Network Adapters Devices that enable computers to communicate on a network Network interface cards (NICs) Three functions Generate network transmission signals Create data packets Act as information gatekeepers Ethernet compliant Wireless NICs Network adapters are devices that perform specific tasks that enable computers to communicate on a network. Most network adapters are installed inside computers and peripherals. These adapters are referred to as network interface cards (NICs). Network adapters perform three critical functions: They generate high-powered signals to enable network transmissions. They break the data down into packets and prepare them for transmission across the network. They act as gatekeepers for information flowing to and from the client computer. Although there are different types of network adapters, Ethernet (wired or wireless) is the standard used on most client/server networks. Therefore, the adapter cards shipping with computers today are always Ethernet compliant. Computers that connect to the network using wireless access need to have wireless network interface cards (wireless NICs) installed in the system unit. Notebook computers and other portable computing devices contain wireless NICs. To allow wireless connections, the network must be fitted with devices called wireless access points. The wireless access point (WAP) gives wireless devices a sending and receiving connection point to the network. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Network Navigation Devices
Media access control (MAC) address Six two-position characters (such as 01:40:87:44:79:A5) Physical address of network adapter Internal network identification 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. A MAC address is used for identification purposes internally on a network, similar to giving people different names to differentiate them. A MAC address is not the same things as an Internet Protocol (IP) addresss. MAC addresses help enhance network security. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Network Navigation Devices (cont.)
Switches and bridges Send data on a specific route through the network Bridges send data between collision domains Routers Send information between two networks 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 ensure that each node receives only the data intended for it. Bridges are devices that send data between different collision domains. Routers are designed to send information between two networks. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Network Security Threats
Human errors and mistakes Malicious human activity Current and former employees hacking or planting viruses Natural events and disasters Hurricanes, floods, fire Sources of network security threats include the following: Human errors and mistakes: Mistakes can be made in input or deletion, or physical accidents can cause damage. Malicious human activity: Current employees, former employees, or a third party might plant a virus, hack into a system to steal data, or deliberately destroy data. Natural events and disasters: Natural disasters like hurricanes and floods can destroy equipment and data. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Network Security Authentication Access privileges
User ID and password used to access the network Use of biometric devices Use of a possessed object for access Access privileges Enable access to certain network systems Physical protection measures Restrict physical access to sensitive network equipment Magnetic card readers Biometric access devices Authentication is the process whereby users prove they have authorization to use a computer network. This could be providing a user ID and password or it can also be achieved through the use of biometric devices and through possessed objects. Examples of possessed objects include identification badges, magnetic key cards, and smart keys. Each user has access privileges that indicate which systems a user is allowed to use. Physical protection of key equipment is accomplished by keeping servers in areas with highly limited access. These areas often have biometric access protection or special access cards. A biometric authentication device uses some unique characteristics of human biology to identify authorized users. Some devices use fingerprints, retina scans, or facial recognition. These devices can be fooled; research is leading to newer biometric methods, but none are yet perfected. Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Network Security (cont.)
Firewalls Prevent access to the network by unauthorized users Composed of software, hardware, or both Screen and validate data packets Bastion host/proxy server Firewalls prevent access to the network by unauthorized users. Most firewalls work as packet screeners. Packet screening involves examining incoming data packets to ensure they originated from or are authorized by valid users on the internal network. The router is the device that performs the packet screening. Unauthorized or suspect packets are discarded by the firewall prior to reaching the network. Most large networks add a bastion host—a heavily secured server located on a special perimeter network between the company’s secure internal network and the firewall. A bastion host gets its name from the fortified towers (called bastions) located along the outer walls of medieval castles, which were specifically designed to defend the castles against attackers. Bastion hosts are often configured as proxy servers. A proxy server acts as a go-between for computers on the internal network and the external network (the Internet). All requests from the internal network for Internet services are directed through the proxy server. Copyright © 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 © Pearson Education, Inc. Publishing as Prentice Hall

Chapter 12 Summary Questions
What are the advantages of a business network? What are the advantages of a business network? Copyright © 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? Copyright © Pearson Education, Inc. Publishing as Prentice Hall

What are the various network topologies (layouts), and why is network topology important in planning a network? What are the various network topologies (layouts), and why is network topology important in planning a network? Copyright © Pearson Education, Inc. Publishing as Prentice Hall

What types of transmission media are used in client/server networks? What types of transmission media are used in client/server networks? Copyright © 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? What software needs to run on computers attached to a client/server network, and how does this software control network communications? Copyright © Pearson Education, Inc. Publishing as Prentice Hall

How do network adapters enable computers to participate in a client/server network? How do network adapters enable computers to participate in a client/server network? Copyright © Pearson Education, Inc. Publishing as Prentice Hall

Copyright © 2012 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 © 2012 Pearson Education, Inc. Publishing as Prentice Hall 47 Chapter 12

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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