In Lesson 1, we discussed LANs and WANs. When we define a network in these terms, we are taking into account the size and geographic area of the network. How the computers in the network are configured and how they share information determine whether the network is peer-to-peer or serverbased—another important network classification. This lesson explores the major features and advantages of these kinds of networks.
After this lesson, you will be able to:
- Identify a peer-to-peer network.
- Identify a server-based network.
- Identify server functions and assign specialized servers as needed.
- Determine which type of network is appropriate for a site.
Estimated lesson time: 45 minutes
In general, all networks have certain components, functions, and features in common, shown in Figure 1.9. These include:
Figure 1.9 Common network elements
Even with these similarities, networks are divided into two broad categories, illustrated in Figure 1.10:
Figure 1.10 Typical peer-to-peer and server-based networks
The distinction between peer-to-peer and server-based networks is important because each type has different capabilities. The type of network you choose to implement will depend on factors such as the:
In a peer-to-peer network, there are no dedicated servers, and there is no hierarchy among the computers. All the computers are equal and therefore are known as peers. Each computer functions as both a client and a server, and there is no administrator responsible for the entire network. The user at each computer determines what data on that computer is shared on the network. Figure 1.11 shows a peer-to-peer network in which each computer functions as both a client and a server.
Figure 1.11 Peer-to-peer network computers act as both clients and servers
Peer-to-peer networks are also called workgroups. The term "workgroup" implies a small group of people. There are typically 10 or fewer computers in a peer-to-peer network.
Peer-to-peer networks are relatively simple. Because each computer functions as a client and a server, there is no need for a powerful central server or for the other components required for a high-capacity network. Peer-to-peer networks can be less expensive than server-based networks.
In a peer-to-peer network, the networking software does not require the same standard of performance and level of security as the networking software designed for dedicated servers. Dedicated servers function only as servers and not as clients or workstations. They are discussed in more detail later in this lesson.
Peer-to-peer networking is built into many operating systems. In those cases, no additional software is required to set up a peer-to-peer network.
In typical networking environments, a peer-to-peer implementation offers the following advantages:
Peer-to-peer networks are good choices for environments where:
Where these factors apply, a peer-to-peer network will probably be a better choice than a server-based network.
Although a peer-to-peer network might meet the needs of small organizations, it is not appropriate for all environments. The rest of this section describes some of the considerations a network planner needs to address before choosing which type of network to implement.
Network administration tasks include:
In a typical peer-to-peer network, no system manager oversees administration for the entire network. Instead, individual users administer their own computers.
All users can share any of their resources in any manner they choose. These resources include data in shared directories, printers, fax cards, and so on.
In a peer-to-peer environment, each computer must:
While a server-based network relieves the local user of these demands, it requires at least one powerful, dedicated server to meet the demands of all the clients on the network.
On a computer network, security (making computers and data stored on them safe from harm or unauthorized access) consists of setting a password on a resource, such as a directory, that is shared on the network. All peer-to-peer network users set their own security, and shared resources can exist on any computer rather than on a centralized server only; consequently, centralized control is very difficult to maintain. This lack of control has a big impact on network security because some users may not implement any security measures at all. If security is an issue, a server-based network might be a better choice.
Because every computer in a peer-to-peer environment can act as both a server and a client, users need training before they are able to function properly as both users and administrators of their computers.
In an environment with more than 10 users, a peer-to-peer network—with computers acting as both servers and clients—will probably not be adequate. Therefore, most networks have dedicated servers. A dedicated server is one that functions only as a server and is not used as a client or workstation. Servers are described as "dedicated" because they are not themselves clients, and because they are optimized to service requests from network clients quickly and to ensure the security of files and directories. Server-based networks (see Figure 1.12) have become the standard models for networking.
Figure 1.12 Server-based network
As networks increase in size (as the number of connected computers, and the physical distance and traffic between them, grows), more than one server is usually needed. Spreading the networking tasks among several servers ensures that each task will be performed as efficiently as possible.
Servers must perform varied and complex tasks. Servers for large networks have become specialized to accommodate the expanding needs of users. Following are examples of different types of servers included on many large networks. (See Figure 1.13.)
File and Print Servers
File and print servers manage user access and use of file and printer resources. For example, when you are running a word-processing application, the word-processing application runs on your computer. The word-processing document stored on the file and print server is loaded into your computer's memory so that you can edit or use it locally. In other words, file and print servers are used for file and data storage.
Application servers make the server side of client/server applications, as well as the data, available to clients. For example, servers store vast amounts of data that is organized to make it easy to retrieve. Thus, an application server differs from a file and print server. With a file and print server, the data or file is downloaded to the computer making the request. With an application server, the database stays on the server and only the results of a request are downloaded to the computer making the request.
A client application running locally accesses the data on the application server. For example, you might search the employee database for all employees who were born in November. Instead of the entire database, only the result of your query is downloaded from the server onto your local computer.
Mail servers operate like application servers in that there are separate server and client applications, with data selectively downloaded from the server to the client.
Fax servers manage fax traffic into and out of the network by sharing one or more fax modem boards.
Communications servers handle data flow and e-mail messages between the servers' own networks and other networks, mainframe computers, or remote users who dial in to the servers over modems and telephone lines.
Directory Services Servers
Directory services servers enable users to locate, store, and secure information on the network. For example, some server software combines computers into logical groupings (called domains) that allow any user on the network to be given access to any resource on the network.
Planning for specialized servers becomes important with an expanded network. The planner must take into account any anticipated network growth so that network use will not be disrupted if the role of a specific server needs to be changed.
Figure 1.13 Specialized servers
A network server and its operating system work together as a unit. No matter how powerful or advanced a server might be, it is useless without an operating system that can take advantage of its physical resources. Advanced server operating systems, such as those from Microsoft and Novell, are designed to take advantage of the most advanced server hardware. Network operating systems are discussed in detail in Chapter 4, "Survey of Network Operating Systems," and Chapter 8, "Designing and Installing a Network."
Although it is more complex to install, configure, and manage, a server-based network has many advantages over a simple peer-to-peer network.
A server is designed to provide access to many files and printers while maintaining performance and security for the user.
Server-based data sharing can be centrally administered and controlled. Because these shared resources are centrally located, they are easier to find and support than resources on individual computers.
Security is often the primary reason for choosing a server-based approach to networking. In a server-based environment, one administrator who sets the policy and applies it to every user on the network can manage security. Figure 1.14 depicts security being centrally administered.
Figure 1.14 One administrator handles network security
Backups can be scheduled several times a day or once a week depending on the importance and value of the data. Server backups can be scheduled to occur automatically, according to a predetermined schedule, even if the servers are located on different parts of the network.
Through the use of backup methods known as redundancy systems, the data on any server can be duplicated and kept online. Even if harm comes to the primary data storage area, a backup copy of the data can be used to restore the data.
Number of Users
A server-based network can support thousands of users. This type of network would be impossible to manage as a peer-to-peer network, but current monitoring and network-management utilities make it possible to operate a server-based network for large numbers of users.
Client computer hardware can be limited to the needs of the user because clients do not need the additional random access memory (RAM) and disk storage needed to provide server services. A typical client computer often has no more than a Pentium processor and 32 megabytes (MB) of RAM.
The following points summarize the main elements of this lesson:
Table 1.1 Comparison of Network Types
|Consideration||Peer-to-Peer Network||Server-Based Network|
|Size||Good for 10 or fewer computers||Limited only by server and network hardware|
|Security||Security established by the user of each computer||Extensive and consistent resource and user security|
|Administration||Individual users responsible for their own administration; no full-time administrator necessary||Centrally located for network control; requires at least one knowledgeable administrator|