Network Operating Systems

Unlike operating systems, such as DOS and Windows95, that are designed for single users to control one computer, network operating systems (NOS) coordinate the activities of multiple computers across a network. The network operating system acts as a director to keep the network running smoothly.

The two major types of network operating systems are:

Peer-to-Peer

Peer-to-peer network operating systems allow users to share resources and files located on their computers and to access shared resources found on other computers. However, they do not have a file server or a centralized management source (See fig. 1). In a peer-to-peer network, all computers are considered equal; they all have the same abilities to use the resources available on the network. Peer-to-peer networks are designed primarily for small to medium local area networks. AppleShare and Windows for Workgroups are examples of programs that can function as peer-to-peer network operating systems.

[peer-to-peer network image]
Fig.1. Peer-to-peer network

Advantages of a peer-to-peer network:

Less initial expense - No need for a dedicated server.
Setup - An operating system (such as Windows 95) already in place may only need to be reconfigured for peer-to-peer operations.

Disadvantages of a peer-to-peer network:

Decentralized - No central repository for files and applications.
Security - Does not provide the security available on a client/server network.

Client/Server

Client/server network operating systems allow the network to centralize functions and applications in one or more dedicated file servers (See fig. 2). The file servers become the heart of the system, providing access to resources and providing security. Individual workstations (clients) have access to the resources available on the file servers. The network operating system provides the mechanism to integrate all the components of the network and allow multiple users to simultaneously share the same resources irrespective of physical location. Novell Netware and Windows NT Server are examples of client/server network operating systems.

[client/server network image]
Fig.2. Client/server network

Advantages of a client/server network:

Centralized - Resources and data security are controlled through the server.
Scalability - Any or all elements can be replaced individually as needs increase.
Flexibility - New technology can be easily integrated into system.
Interoperability - All components (client/network/server) work together.
Accessibility - Server can be accessed remotely and across multiple platforms.

Disadvantages of a client/server network:

Expense - Requires initial investment in dedicated server.
Maintenance - Large networks will require a staff to ensure efficient operation.
Dependence - When server goes down, operations will cease across the network.

Examples of network operating systems

The following list includes some of the more popular peer-to-peer and client/server network operating systems.