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Network Components
A Network Operating System (NOS) controls the interaction between all the machines on the network. The network operating system is responsible for controlling the way information is sent over the network medium and handles the way data from one machine is packaged and send to another. The NOS also has to handle what happens when two or more machines try to send at the same time. • Local area networks that have a single server with many clients connected to it who put the NOS on the server. The main part of the NOS sits on the server, while the smaller client software packages are loaded onto each client. • With larger networks that don't use a single server, such as a network running TCP/IP, the NOS may be part of each machine's software. A Network Interface Card (NIC) is an adapter that usually sits in a slot inside the PC. Some NIC’s can plug into parallel or SCSI ports. The network interface card handles the connection to the network itself through one or more connectors on the backplane of the card. You must make sure that the network interface card you are using in your machine works with the network operating system.
Figure 5 shows the symbol used for a Network Interface Card. A Client is any machine that request something from a server. The server supplies files and sometimes processing power to the smaller machines connected to it. Each machine is a client in this type of network.
Figure 6 shows the symbol used for a Client. A Server is any machine that can provide files, resources, or services to another machine. Any machine that you request a file from is a server. This is the essence of client-server networks: One machine, the client, request something from another machine, the server. A single machine may be both client and server. The more commonly used definition for a server is related to local area networks, where the server is a powerful machine that holds main files and large applications. Other machines on the network connect to the server to access those files and applications. In this type of network, a single machine usually acts as the server and all the other machines are clients. Simply put, the server is any machine on the network that your machine request something from.
Figure 7 shows the symbol used for a Server. In the Client-Server model, a client is the machine that initiates a request to a server. This type of terminology is common with TCP/IP networks, where no single machine is a central repository.
Figure 8 shows a Client-Server model. A Local Resource is any peripheral (optical drive, printer, scanner, modem, and so on) that is attached to your machine. Since the machine doesn't have to go on the network to get to the device, it is called a local device or a local resource.
Figure 9 shows Local Resources. A Remote Resource is any device that must be reached through the network. Any devices attached to a server, are remote resources.
Figure 10 shows Remote Resources. A Node is any device on a network (server, workstation, printer, scanner, or any other kind of peripheral) that is accessed directly by the network. A node has a unique name or IP address so the rest of the network can identify it.
A Concentrator is a device that concentrates several network connections at a single point. It is a electronic unit that converts signals coming from different slower devices to a signal that can be transmitted over faster communication-channels with a bigger bandwidth.
Figure 12 shows the symbols used for a Concentrator. A Hub is a multipurpose network device that lies at the centre of a star-topology network. Most hubs do the same job as concentrators. Hubs support a variety of different interface cards, from concentrator cards to router cards. Hubs are also expandable within a single chassis. Despite these differences, the term hub and concentrator are often used interchangeably. There are active and passive hubs.
Figure 13 shows the symbol used for a Hub. A Repeater is a network device that boosts the power of incoming signals to allow the length of a network to be extended.
Figure 14 shows the symbol used for a Repeater. A Bridge is a network device capable of connecting networks that use similar protocols. It connects two local area networks running the same network operating system.
Figure 15 shows the symbol used for a Bridge. A Router is a network device that connects LAN’s, that may be running on different operating systems, into an internetwork and routes traffic between them. The router can have software that converts on NOS's packets to the other's. A router is more complicated than a bridge in that it can make decisions about where and how to send packets of information.
Figure 16 shows the symbol used for a Router. A Gateway forwards data between IP networks. It is a machine that acts as an interface between a small network and a much larger one, such as a local area network connecting to the internet. Gateways are also used in large corporations to connect small office-based LAN’s into the larger corporate mainframe networks. Usually, the gateway connects to a high-speed network cable or medium called the backbone.
Figure 17 shows the symbol used for a Gateway. A Backbone is a set of nodes and links connected together comprising a network, or the upper layer protocols used in a network. A star network has no backbone.
Figure 18 shows the symbol used for a Backbone.
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