NETWORK CATEGORIES

A network is defined as two or more computers attached to each other that share information. Networks can be formed to make up an LAN or a WAN. An LAN is a network that resides in one physical location, such as a building. It usually has a limited number of computers attached to it and is designated a certain scope or range of computer IP numeric addresses. A WAN is a larger network that usually combines two or more LANs together over a larger physical distance. For example, a business may have two LANs in different buildings or different cities. The two LANs can be connected to form a WAN. A WAN typically has a larger range of computer IP addresses and is used to control communication between LANs. Access to a WAN is usually accomplished through use of a leased or dedicated T1 line, or a dial-up modem connection using ISDN, cable, or DSL.

There are two basic types of networks in use today: peer-to-peer and server-based. Each of the two network categories has its own set of built-in characteristics that differentiate it from the other.

Peer-To-Peer Networks

A peer-to-peer network is a small network, usually of 10 or fewer computer systems, connected without the use of a larger specialized server computer. In peer-to-peer networks, a workstation can function as both a client and a server computer. In other words, a single computer can share information or devices attached to it or act as its own entity to carry out day-to-day workstation functions.

A peer-to-peer network does not require a high-end server computer to provide login authentication or a highly trained staff to secure and administer network resources. A peer-to-peer network uses password-protected shares that utilize share-level security at the workstation level. The user of the workstation decides who will be able to read, write, execute, or delete files that exist. Windows 3.11, 95, 98, Me, NT, 2000 and Windows XP operating systems can all provide peer-to-peer capabilities.

Many small businesses and home enthusiasts implement peer-to-peer networks. They are a less expensive alternative to server-based networks and are fairly easy to maintain, as long as you remember all the passwords that may be associated with all the files, folders, and devices.

Server-Based Networks

A server-based network is typically implemented for networks that have more than 10 computers and that require quick access to services that specialized high-end servers can provide. A server-based network is designed to centralize the control and administration of network access (security) and resources. When a user logs on to a server-based network, a specialized server that controls network access authenticates the user by utilizing user-level security. A network administrator or manager is typically empowered in a server-based network to control, monitor, and carry out the daily network maintenance associated with this type of network. Some examples of operating systems that can provide server-based functionality are Microsoft Windows NT Server, Windows 2000 Server, Windows Server 2003, Novell Netware, and Unix.

Server computers are designed to provide specific services to client computers. Some of the different types of server computers are listed in Table 22.1.

Table 22.1: Types of Network Server Computers

Server Type	Server Function
Authentication Server	Centralized location of security accounts database used to allow users access to the network—for example, Windows NT Primary Domain Controller. (PDC)
Database Server	Houses the common database. Is responsible for storage and management of data warehouse services—for example, Microsoft SQL Server.
Application Server	Handles high-end operations to take load off of client computers. Application software is installed on a server. Client computers request services from the application server.
Print Server	Handles all client side requests for network printing. Manages network printers and print queues.
Communications Server	Responsible for e-mail, fax, Internet access and dial-up modem connections. Microsoft Exchange Server is an example of a communications server application.
Web Server	Serves up Internet or intranet Web pages—for example, a server that runs Microsoft Internet Information Services (IIS) or Samba.

Network Redirector

The network redirector is software that is built into the code of a network operating system. The redirector intercepts requests made by the system’s processor and decides whether the request should be forwarded to another system on the network or remain local to the system. If a request is made from a client workstation for a particular instruction, such as printing to a network printer, the redirector grabs the request and sees that it is forwarded to the network so that print operations can commence.

Universal Naming Convention

A Universal Naming Convention (UNC) name is used to access a particular share on a particular workstation or server on a network. If you want to access a resource, such as a printer or folder that has been shared on the network, you can gain access to it by typing in the UNC name from the Start > Run option in Windows. A UNC name always follows the format \\Servername\sharename. For example, suppose you want to access a folder on the network named “Certified.” The Certified folder resides on a server named “Bigserver.” You would go to Start > Run and type in \\Bigserver\Certified. If you have rights to the Certified folder, you can have access to it.