Notes

A network operating system (NOS) is an operating system that runs on computers connected across a network. Some common examples of a NOS include Microsoft Windows Server, Linux, IBM OS/2, and Mac OS X.

A NOS is an important component of a network system. It supports the functions of workstations and servers in the network. Before setting up a network system, you need to decide on the NOS that you will install on the network. The features of the NOS will determine how you configure your network.

Let's discuss some of the common features of NOS.

Network Support
A NOS facilitates the connectivity between users and devices. It balances the workload of the computers and devices connected to the network.

The file sharing services of the NOS enable resource sharing among network users. The most common shared resource is the server's file system. It is the organized disk space on the server that users can share. The operating system enables an administrator to decide which parts of the server's file system to share.

Multitasking
The NOS applies multitasking to reduce processing time. Multitasking is when different users run multiple programs at the same time. The operating system switches the CPU time between the programs. This gives the impression that several programs are running simultaneously.

Directory Services
Directory services are essential parts of the NOS. They contain information about network resources such as files, computers, printers, and shared folders. Administrators, too, use directory services to locate resources and to set up permissions for users to access them.

Security Services
A NOS provides security features to prevent a hacker's unauthorized access to the network. The simplest way to ensure security for genuine users is to create user accounts. These user accounts not only grant access to network resources but also determine which resources a genuine user can access. Let's look at two of the standard security tools that a NOS provides.

Password policies: Passwords secure user accounts. A common way to ensure a strong password is to define a password policy. This policy defines the minimum length of the password and the combination of numerals and alphabetic and special characters that the password allows. This policy may also require users to change passwords frequently.

Network encryption and security certificates: Network encryption means that data is scrambled before the NOS sends it out on a network, thereby making it difficult for hackers to get unauthorized access to the network. Security certificates identify and authenticate users. They also help validate documents.

Networking Technologies
Intranets and extranets use the same technology as the Internet. However, intranets and extranets are restricted networks that only allow users with the necessary rights to access data and web pages on the network. Both small and large organizations use these systems. Intranets and extranets enable secure communication, and they play an important role in the management of internal communications.

You can think of an intranet as a private version of the Internet. Intranets help protect information, speed up workflow, and ultimately save money. Company personnel use intranets to share various files, multimedia clips, forms, policies, payroll information, and so on within the company. Intranets restrict data access to the appropriate people within a company. People typically can't access an intranet outside the physical boundary of the organization or through the Internet. You can protect intranets from external intrusions with firewalls. A firewall is a security system that filters what goes in and out of a network according to predefined rules.

Extranets are similar to intranets, except that they allow authorized outsiders such as business partners, suppliers, and customers to access secure information. For example, an extranet is useful when suppliers need to access or update the inventory of the organization for which they supply materials. The organization provides access to the inventory through its extranet. Extranets are also useful when employees need to work from home or as they travel, as well as when the company must share information with customers.

Organizations also use the Internet for communication. Usernames and passwords limit access to private networks such as intranets and extranets. Everyone, however, can access data on the Internet. You do not need a username and password to access this data.

The Internet is a global network that allows businesses to interact with entities that are not on the local network. These entities include customers, vendors, suppliers, and government bodies. Businesses use the Internet to market their products and sell online.

An intranet is an internal network set up to provide uninterrupted communication and data storage. It provides a secure space where authorized users can store and access corporate data. Organizations also use the intranet to update their employees with the most current policies and news.

An extranet can connect various intranets. It enables different companies to work on joint projects and share information. It also enables a company to connect with partners who may not be on the intranet.

Network Media
Computer networks use wire-based as well as wireless media to connect computers and devices to transfer data. Most wire-based media uses physical wires. They are made of different combinations of copper wires to conduct signals. They also have insulators. Alternatively, wires may contain fiber-optic glass strands. Wireless media, on the other hand, uses air as a medium to transmit radio, infrared, or microwave signals.

Twisted-pair cables contain four pairs of plastic-covered wires. Each pair contains two individually insulated wires twisted around each other. The number of pairs of wires may differ. Two varieties of twisted pair cables are as follows:

Unshielded twisted-pair (UTP) wires have plastic coating that separates the wires from the outside.
Shielded twisted-pair (STP) wires have a metal sheath that reduces electrical interference.
Improved twisted-pair wires can now reach transmission speeds of 1 Gbps. They are flexible and minimize crosstalk. However, they are susceptible to electromagnetic interference. Telephone systems use twisted pair cables.

Coaxial cables consist of two conductors, a central wire, and a surrounding wire mesh, separated by an insulator. They can reach transmission speeds of 10 Mbps, but they are more expensive than twisted-pair cables. Cable television systems use coaxial cables.

Fiber-optic cables contain thin glass strands covered with insulation. These cables transmit signals in the form of light instead of electric current. They can reach transmission speeds of 100 Gbps and transmit a large volume of signals simultaneously. Fiber-optic cables are immune to interference.

Wireless media uses different regions of the electromagnetic spectrum to transmit signals through air. The type of electromagnetic radiation depends on the distance the signal needs to travel, the type of network, and the device acting as a node (for example, a laptop). Wireless communication often uses radio, infrared, and microwave signals to transmit data. Long-distance transmissions use satellites and wireless media to connect computers, servers, and other nodes within a building, from one building to another, or to a home base that mobile users can access.

A protocol is a set of rules for devices to exchange data. For example, when a device accesses data from another device, a protocol defines their interactions. Essentially, protocols are universal standards of communication.

A number of communication protocols exist, each intended for a particular type of network connection. Some protocols regulate data transfer, whereas others define security or access control.

Transmission Control Protocol/Internet Protocol (TCP/IP): This protocol has two parts: TCP and IP. TCP defines how to break data down into small packets and transmit it over a network. TCP also manages packets and checks errors to avoid packet loss. IP defines data packet addresses and routes each packet to the correct recipient.
Hypertext Transfer Protocol (HTTP): This protocol defines how to transmit and display information on browsers through web pages on the Internet. The variant HTTPS (the S stands for "Secure") defines secure HTTP transfers. Entering a web address in a browser sends a command to the web server directing it to find and transmit the web page.
File Transfer Protocol (FTP): FTP uses the Internet's TCP/IP protocols to enable data transfer. FTP provides simple file management and allows users to share files.
Telnet: Telnet runs on your computer and connects it to a server on the network. You can then enter commands just as you would on a server. You can control the server and communicate with other servers on the network. This enables you to control web servers from remote locations.

Network Troubleshooting Techniques
Network problems occur for many reasons. Let's discuss some of the common network issues.

Connectivity issues: Connectivity issues can arise if incorrect configurations cause malfunctions in connectivity components, such as bridges or hubs.

Cable problems: Cables that connect parts of a network can cause short connections if they are exposed or if their outer protective covering deteriorates.

Duplicate IP addressing: A common issue in many networks results when two devices use the same IP address. This may cause irregular signals over the network.

Excessive network collisions: Excessive network collisions occur due to a bad network setup or a high volume of data that slows down a network considerably. Sometimes, a network slows down when a network card is locked in a perpetual "transmit" mode. The transmit light shows that the network is transmitting data.

Software problem: Administrators can often trace network problems back to faulty software configurations. These can include Windows Internet Name Service (WINS) configurations, Domain Name System (DNS) configurations, or registry settings.

Problems connecting to the Internet: If you have problems connecting to the Internet, you should check whether your computer has an IP address. You can use the ipconfig command to verify the IP address. You should also check whether the computer can connect to the correct gateway.

Problems with accessing network applications: If you have trouble working with certain network applications, you should check whether your computer can connect to the proper network and server. You can use the Ping command to determine whether the server is running.

Problems with accessing shared files and folders: If you can't access shared files and folders on your network, check whether you have the proper permissions to access them. You may need the help of the network administrator to get access to these files.

Network problems sometimes occur when you have cable problems that are not visible to the naked eye.

If your network uses a twisted pair cable, you can determine if the cable connection is good by checking a small light at the back of the computer where the cable plugs in. If the light glows steadily, the cable is good. If it is not lit, or if it flashes, then you have a cable problem. You can try removing the cable and plugging it in again. This may solve the problem.

If your computer connects to a network through a patch cable that's giving you a problem, try to quickly remove it and insert it again. If that doesn't work, you may have to replace it with a spare patch cable.

Make sure that all the wires and cables are plugged in.
Make sure that your computer draws power from the outlet.
Check if your computer or server has run out of free disk space.
If your electrical surge protector is more than three years old, you may need to replace it.
If you face any problems with the network, try restarting your computer.
Note any error messages that appear on the screen.