The Network Operating System

Now that you have looked at the typical hardware components of a LAN, let us look at another very essential element of the LAN, namely its operating system (OS). The operating system in a computer, as you know, performs the task of storage management of data and programs and the functions of input-output device management.

A LAN or any other type of network also needs an operating system. There is one vital difference between a network operating system and a single-user operating system like DOS. DOS concerns itself with the operations of a single PC. A network operating system has to concern itself with the management of the network as a whole. It has to ensure that the network of computers operates smoothly.

Some of the tasks that a network operating system performs are listed hereunder:

• The network OS provides network services to users. The network services are:
• Access to disk storage space: Network users can save files in a common location, i.e. the server hard disk. It is necessary to ensure that every user gets a share of disk space on the server disk.
• Access to shared files: In a network, certain files on the server can be accessed by several workstations at the same time. The network operating system ensures that this takes place smoothly.

• The network OS takes care of security, ensuring that files of one user are not accessed by other users.
• It manages the sharing of peripherals like printers among workstations.

Some of the most popular network operating systems in use are -Novell NetWare from Novell Inc., Windows NT Server from Microsoft.

What are the Functions of a Network Operating System?

The network operating system provides network services to the users, takes care of the security and manages peripherals like printers among workstations.

Network Operating System

A network operating system does everything a stand alone operating system does, and more in a much more complex environment. In addition to the usual lower level computing tasks, a network operating system is responsible for all the following tasks:

• Directing data traffic through the network
• Allowing and preventing access to data based on security requirements
• Preventing access to data files while they are being processed
• Managing the flow of information between a variety of workstations
• Managing requests for printer services
• Managing communication and messages between network users
• Managing connections between the network and remote sites
• Make services as transparent as possible to the user

Components of the Network Operating System

There are two main components of the network operating system. They are:

• Client software - installed on clients.
• Server software - installed on servers.

Client Software

In a network environment, when a user initiates a request to use a resource that exists on a server in another part of the network, the request has to be forwarded or redirected to the server with the requested resource. The component of the client software that does this task is the redirector.

Redirector

The redirector may also be referred to as a shell or a requester. It is a small part of the network operating system that:

• Intercepts requests in the computer.
• Determines if the requests can be serviced by the local system itself or it needs to be forwarded to the server.

Designators

A designator is an alphabet that is assigned to each network resource. The redirector keeps track of which drive designators are associated with which network resources.

For example, to access a particular shared directory on a remote computer, we can assign a letter of the alphabet, say H, to it. We can then refer to the shared directory on the remote computer as H and the redirector will locate it.

Server Software

Server software makes it possible for users working on other machines to share the server's data and peripherals including shared directories, printers, plotters and disks.

Resource Sharing

The server software not only allows sharing of resources, but also determines the degree of sharing. The degree of sharing includes:

• Allowing different users different levels of access to the resources. For example, a file server could give read or write or read and write permissions to different users.
• Coordinating access to the resources to make sure that two users do not use the same resource at the same time.

Managing Users

Network operating systems make it possible for a network administrator to determine who will be able to use the network. The server software can be used to:

• Create user privileges, which indicates who gets to use the various resources on the network.
• Validate user names and passwords at the time of logging on.
• Grant or revoke user privileges on the network.
• Remove users from the list of users having access to the server.

Network Services

Network services are network operating application programs that run on the network. The network operating system installation program ensures that the user has a minimum of network services installed by default.

Some examples of services installed by the NT operating system, by default are:

• Alerter service - notifies selected users and computers, of administrative alerts that occur on the computer. As an example, an alerter service could be set to issue alerts whenever the used space of a hard disk exceeds a particular percentage of the total hard disk space.
• Event log service - records system, security and program events in the event log.
• Messenger service - sends and receives messages sent by administrators or by the alerter service.
• Other services such as the telephony service, which is used by programs to make data, fax, voice calls. These services have to be manually started by the user.

Shared Network Applications

Applications such as word processors and databases can be shared on the network like any other resource.

The advantages of shared network applications are:

• It makes application programs less expensive because buying a site license for 200 users on an application is usually cheaper than buying 200 individual copies of the application.
• It ensures that everyone will be using the same version of the product.
• The information in the database that is stored on the server, can be accessed by the clients on remote machines. This model of the client/server network is the most efficient way for:
• Database access and management.
• Network management.
• Centralized file storage.