MCSE Traing Guide Networking Essentials

8/28/98 11:26 AM Page 11 C hapter 1 NETWORKING TERMS AND CONCE PT S the drawbacks, however, was that the mainframes were not flexible in their placement (some were the size of a large room) and did not scale down to meet the needs of smaller organizations. New ways of sharing information were necessary to allow computing power to be shared efficiently on smaller networks. Distributed Computing As personal computers (PCs) were introduced to organizations, a new model of distributed computing emerged. Instead of concentrating computing at a central device, PCs made it possible to give each worker an independent, individual computer. Each PC could receive input and could process information locally, without the aid of another computer (see Figure 1.4). NOTE 05.919-x CH01.i Personal Computer Terminology. The term PC initially referred to a specific device—the IBM PC computer. Over time, PC has become a generic term referring to any desktop computer. Some purists, however, still use the term PC to refer to an IBMcompatible workstation computer and use the term Mac to refer to a computer from Apple. This meant that groups who previously had found the cost of a mainframe environment to be prohibitive were now able to gain the benefits of computing at a far lower cost than that of a mainframe. These PCs, however, did not have the computing power of a mainframe. Thus, in most instances, a company’s mainframe could not be replaced by a PC. An analogy might help clarify the difference between the two computing models. A mainframe, which uses a centralized computing model, is like a bus. A bus is a large, powerful vehicle used to transport many people at once. Everyone goes to one location—the bus—to be transported. In the same way, everyone must work 70% of the processing 30% of the processing Information flows FIGURE 1.4 Distributed computing. 11

05.919-x CH01.i 12 8/28/98 11:26 AM C h a p te r 1 Page 12 NE TWO R KI NG TE R MS AND CONCEPTS through or at a mainframe computer. A personal PC, which uses distributed computing, is like a motorcycle. It transports one person at a time. (Yes, I know a motorcycle can transport two people, but think of it as only having one seat.) Each person can use his own motorcycle to go somewhere without worrying about the other users. PCs enable individuals to work at their own computers rather than through a single large computer. In summary, distributed computing involves the following: á Multiple computers capable of processing independently á Task completion by the local computer or other computers on the network Distributed computing was a major step forward in how businesses leveraged their hardware resources. It provided smaller businesses with their own computational capabilities, enabling them to perform less-complex computing tasks on the smaller, relatively inexpensive machines. Collaborative Computing Also called cooperative computing, collaborative computing enables computers in a distributed computing environment to share processing power in addition to data, resources, and services. In a collaborative computing environment, one computer might borrow processing power by running a program on another computer on the network. Or, processes might be designed so they can run on two or more computers. Collaborative computing cannot take place without a network to enable the various computers to communicate. A person browsing the Internet is an example of collaborative computing. On the Internet, Web servers actively use resources to give your computer information about how a Web page should look, includings its colors, its font sizes, and what graphics should display. Your computer uses its processing power to interpret this information and to display it in the format intended by the designer. Another example of collaborative computing is Microsoft serverbased products such as Exchange Server or SQL Server. For both of these products, requests originate from intelligent client software (which uses the processor power of the workstation it is running on)

05.919-x CH01.i 8/28/98 11:26 AM Page 13 C hapter 1 NETWORKING TERMS AND CONCE PT S but then are serviced from server software running on a Windows NT server. The server then processes the request using its own resources and passes the results back to the client. Processor and memory resources on both the client and the server are utilized in the completion of the task. In the future, you can expect collaborative computing to provide even greater amounts of computing power. This might happen through a new capability of computers to detect which PCs are idle on the network and to harness the CPU power or RAM of the idle PCs for use in processing. In summary, collaborative computing involves the following: á Multiple computers cooperating to perform a task á Software designed to take advantage of the collaborative envi- ronment NETWORK MODELS: COMPARING CLIENT/SERVER AND PEER-TO-PEER NETWORKING CONFIGURATIONS Compare a client/server network with a peer-to-peer network. Networks generally fall into one of two broad network categories: á Client/server networks á Peer-to-peer networks It is important to remember that one type of networking configuration is not necessarily better than another. Each type of networking model has its own strengths and weaknesses. Client/Server-Based Networking A client/server network consists of a group of user-oriented PCs (called clients) that issue requests to a server. The client PC is responsible for issuing requests for services to be rendered. The server’s 13

05.919-x CH01.i 14 8/28/98 11:26 AM C h a p te r 1 Page 14 NE TWO R KI NG TE R MS AND CONCEPTS function on the network is to service these requests. Servers generally are higher-performance systems that are optimized to provide network services to other PCs. The server machine often has a faster CPU, more memory, and more disk space than a typical client machine. Some examples of client/server-based networks are Novell NetWare, Windows NT Server, and Banyan Vines. Some common server types include file servers, mail servers, print servers, fax servers, and application servers. In a client/server network, the server machines often are not even set up to do the tasks that a client machine can do. (On a Novell or Banyan server, for example, a person cannot run a spreadsheet from the server console. Other systems, such as Windows NT and UNIX machines, enable a person to do this even though it is not the intended use of the system). Eating at a restaurant is analogous to a client/server model. You, the customer, are a client. You issue requests for meals, drinks, and dessert. The waiter is the server. It is the waiter’s job to service those requests. Although this discussion should have made it clear how they differ, people often confuse mainframe computing with a client/serverbased network. The two approaches to computing are not the same, however. In mainframe computing, the dumb terminal does not process any requests. It simply acts as an interface to receive input and to display output. Only the mainframe computer can process information. In a client/server model, the client PC can process information, but certain services are offloaded to the server machine. The server machine’s role is simply to process the requests made for these services by the client. In short, a client/server-based network is one in which certain tasks run on and utilize the resources of one machine while others utilize another machine, each according to its functional role. An example of a client/server system is Microsoft Exchange Server. Your PC is responsible for constructing and displaying email messages, to name a couple of the possible tasks. The Exchange server is responsible for delivering outgoing email and for receiving email intended for you. In summary, the client/server model is a network in which the role of the client is to issue requests and the role of the server is to service requests.

05.919-x CH01.i 8/28/98 11:26 AM Page 15 C hapter 1 NETWORKING TERMS AND CONCE PT S Peer-to-Peer Networking A peer-to-peer network consists of a group of PCs that operate as equals. Each PC is called a peer. The peers share resources (such as files and printers) just like in a server-based network, although no specialized or dedicated server machines exist. In short, each PC can act as a client or a server. No one machine is set up with a higherpowered set of devices, nor is any one PC set up simply to provide one service (such as storing files). Small networks—usually with fewer than 10 machines—can work well in this configuration. In larger networks, companies usually move to a server-based network because many clients requesting to use a shared resource can put too much strain on one client’s PC. Examples of peer-to-peer networks include Windows for Workgroups, Windows 95, and Windows NT Workstation. Many actual network environments consist of a combination of server-based and peer-to-peer networking models. In the real world, companies often grow from a peer-to-peer network into a client/server-based network. The following analogy might help you better understand the use of each type of network. A small company of 10 employees might choose to implement a carpool strategy. Let’s say four employees get together, and each takes a turn driving the other three employees to work. This is analogous to a peer-to-peer network. Just like a peer-to-peer network, in which no one PC is responsible for dedicating itself to providing a service, no one car is dedicated to providing transportation. As the company grows to 400 employees, it might be decided that the number of employees justifies the purchase of a dedicated ridepool van with a dedicated driver. This is analogous to a client/server network, in which a dedicated machine is used to provide a service. In this example, the company has dedicated a van to providing a ride-share service. As you can see in this analogy, no single network model fits all situations. A car pool in a small company is an efficient and cost-effective way to get people to work. A bus probably is not economically feasible for a small company. In a big company, however, the use of a bus becomes feasible. Peer-to-peer networks can work well for small workgroups. Client/server networks provide the necessary resources for larger groups of users. 15

05.919-x CH01.i 16 8/28/98 11:26 AM C h a p te r 1 Page 16 NE TWO R KI NG TE R MS AND CONCEPTS LOCAL AND WIDE AREA NETWORKS Define common networking terms for LANs and WANs. Networks come in all shapes and sizes. Network administrators often classify networks according to geographical size. Networks of similar size have many similar characteristics, as you will learn in later chapters. The following are the most common size classifications: á Local area networks (LANs) á Wide area networks (WANs) These size classifications are described in the following sections. Local Area Networks (LANs) A local area network (LAN) is a group of computers and network communication devices interconnected within a geographically limited area, such as a building or a campus. LANs are characterized by the following: á They transfer data at high speeds (higher bandwidth). á They exist in a limited geographical area. á Connectivity and resources, especially the transmission media, usually are managed by the company running the LAN. NOTE Wide Area Networks (WANs) WANs Are Interconnected LANs. This interconnection often is represented by a line going into a cloud. This is because the company running the network typically has only a general idea of the path that the data will take on its journey to the other LAN segment. All the company knows is that the data enters the cloud on one side and exits the other side. A wide area network (WAN) interconnects LANs. A WAN can be located entirely within a state or a country, or it can be interconnected around the world. WANs are characterized by the following: á They exist in an unlimited geographical area. á They usually interconnect multiple LANs. á They often transfer data at lower speeds (lower bandwidth). á Connectivity and resources, especially the transmission media, usually are managed by a third-party carrier such as a telephone or cable company.

05.919-x CH01.i 8/28/98 11:26 AM Page 17 C hapter 1 NETWORKING TERMS AND CONCE PT S 17 LAN LAN WAN Links FIGURE 1.5 LAN The WAN or the link up of LAN’s is often shown as a cloud. WANs can be further classified into two categories: enterprise WANs and global WANs. An enterprise WAN connects the widely separated computer resources of a single organization. An organization with computer operations at several distant sites can employ an enterprise WAN to interconnect the sites. An enterprise WAN can combine private and commercial network services, but it is dedicated to the needs of a particular organization. A global WAN interconnects networks of several corporations or organizations. Other terms that describe networks include municipal area network (MAN)—a connected network that spans the geographic boundaries of a municipality—and campus area network (CAN)—a network that spans a campus or a set of buildings. These terms often lead to confusion because people are not sure whether they refer to the company’s own network of computers or its connection to the outside world. INTRANETS AND INTERNETS In recent years, two new terms have been introduced: internet and intranet. A company that has a LAN has a network of computers. As a LAN grows, it develops into an internetwork of computers, referred to as an internet. In the 1990s, graphical utilities (or browsers) were developed to view information on a server. Today, the two most popular forms of this

05.919-x CH01.i 18 8/28/98 11:26 AM C h a p te r 1 Page 18 NE TWO R KI NG TE R MS AND CONCEPTS utility are Microsoft’s Internet Explorer and Netscape’s Navigator. These browsers are used to navigate the Internet (note the capital I). This terminology initially led to much confusion in the industry because an internet is a connection of LANs, and the Internet is the connection of servers on various LANs that is available to various browser utilities. To avoid this confusion, the term intranet was coined. This term describes an internetwork of computers on a LAN for a single organization; the term Internet describes the network of computers you can connect to using a browser—essentially, an internetwork of LANs available to the public. NETWORK SERVICES Network services are the basic reason we connect computers. Services are what a company wants to have performed or provided. Based on the services a company wants to utilize, the company purchases a specific program and operating system. This section describes some of the most common services available on computer networks. Basic Connectivity Services The PCs in a network must have special system software that enables them to function in a networking environment. The first network operating systems really were add-on packages that supplied the networking software for existing operating systems such as MS-DOS or OS/2. More recent operating systems, such as Windows 95 and Windows NT, come with the networking components built in. An analogy might help you differentiate fully integrated systems from add-ons. A box can hold goods, but it is not specifically designed to go anywhere. You can place a set of logs on the ground to act as rollers for the box, thus providing a mechanism for transporting or moving the box. This is similar to how old network systems used to work. Newer operating systems are like trucks. A truck is designed from the ground up with a chassis that supports a box to move goods. The box and the mechanism for transportation (the chassis) are integrated from the beginning; they are designed to operate with each other.

05.919-x CH01.i 8/28/98 11:26 AM Page 19 C hapter 1 NETWORKING TERMS AND CONCE PT S 19 Client and server machines require specific software components. A computer that is strictly a server often cannot provide any client functionality. On a Novell server or a Banyan server, for example, a user cannot use the server for word processing. This is not always the case, however; Microsoft’s NT Server and UNIX servers can run client programs. A computer in a peer-to-peer network functions as both a client and a server; thus, it requires both client and server software. Operating systems such as Windows NT Workstation and Windows 95, both of which are peer-to-peer network operating systems, include dozens of services and utilities that facilitate networking. Some of these components are discussed in other chapters, and some are beyond the scope of the Networking Essentials exam. (You’ll learn about them when you study for the Windows NT Server or Windows NT Workstation exam.) This section introduces you to a pair of key network services—the redirector service and the server service—that are at the core of all networking functions. Redirector Service A network client must have a software component called a redirector. In a typical standalone PC, I/O requests pass along the local bus to the local CPU. The redirector intercepts I/O requests within the client machine and checks whether the request is directed toward a service on another computer. If it is, the redirector directs the request toward the appropriate network entity. The redirector enables the client machine to send information out of the computer, provided that a transmission pathway exists. In some operating environments, the redirector is called the requester. The workstation service acts as a redirector on Windows NT systems. In the field, people often refer to a redirector as a client. To connect a Windows 95 machine to a Windows NT machine, for example, it often is said, “Install the Microsoft Client for Microsoft Networks.” If you want this Windows 95 machine to connect to a Novell server, you might say, “Install a Novell Client on the Windows 95 machine” (see Figure 1.6). Server Service FIGURE 1.6 A network server machine must have a component that accepts I/O requests from clients on the network and that fulfills those requests The dialog box on a Windows 95 machine that shows a redirector being installed.

05.919-x CH01.i 20 8/28/98 11:26 AM C h a p te r 1 Page 20 NE TWO R KI NG TE R MS AND CONCEPTS by routing the requested data back across the network to the client machine. In Windows NT, the server service performs the role of fulfilling client requests. File Services Compare a file and print server with an application server. File services enable networked computers to share files with each other. This capability was one of the primary reasons networking of personal computers initially came about. File services include all network functions dealing with the storage, retrieval, or movement of data files. File services enable users to read, write, and manage files and data. This includes moving files between computers and archiving files and data. This section begins by defining file services and then moves on to other related topics such as file transfers, file storage, data migration, file archiving, and file update synchronization. File services are an important part of client/server and peer-to-peer networks. Computers providing files services are referred to as file servers (see Figure 1.7). Two types of servers exist: dedicated and non-dedicated. Dedicated servers do nothing but fulfill requests to network clients. These servers commonly are found in client/server e

Networking Terms and Concepts Chapter 1 targets the following objectives in the Standards and Terminology section of the Networking Essentials exam: Compare a client/server network with a peer-to-peer network. This objective makes sure you are familiar with the two main network classification models. Define common networking terms for LANs .