Ever since the days of the Pony Express, people have looked to getting information, whether personal or business, to its intended receiver as soon as possible. The computer has evolved as a communications super-tool, enabling people to do just that. Networking has given individuals the power to transfer ideas, reports, and files quickly and efficiently. Networks also grant the power to business professionals and families to conference with voice and video from their individual offices or homes.
These abilities have made networking invaluable to many people in many different areas; however, networking can be imited to a small geographic region or even a single building and still have tremendous benefits. A Local Area Network (LAN) is a network of interconnected workstations sharing the resources of a single processor or server within a relatively small geographic area. LANs can be found in offices, schools, throughout whole buildings, and even dispersed throughout several buildings. Throughout these local networks, people are able to share files of information, communicate, and connect different departments to maximize efficiency.
A LAN is comprised of several pieces of hardware that enable connectivity of the network; hese include network interface cards, servers, bridges, repeaters, and hubs. A LAN can be comprised of all of these parts and more, but can also be constructed of less hardware. The hardware components of a specific network depend on the needs of the network. A network interface card physically connects a computer to a transmission medium used on a network and controls the flow of information from the computer to the network. A network interface card has its own unique hardware address that is embedded upon its manufacturing.
The hardware address is used to identify each NIC when information is being sent or received over a etwork. These cards are installed directly into the expansions slots of a computer and in the case of portable computers require a specialized device called a network adapter. Network interface cards have ports that are used to connect the card to the transmission medium used throughout the network. Different types of cards are designed to accept a certain type of transmission medium or network cable, which in turn determines the amount of information and the speed at which that information can be sent.
The NIC also contains a transceiver, which converts the computer output signal into a signal that can be ransmitted over cable. In some instances a network interface card may also contain a boot chip, which enables a drive-less computer to access a network. Different cards are designed for different purposes, one type of card can be used by a client workstation solely to connect that computer to a network, while others are used by network servers that are specifically designed to transfer large amounts of information.
A hub is a device used to concentrate and organize network wiring. There are two basic types of hubs, active and passive. A passive hub is simply a device that allows wiring connections in an orderly way. It equires no power, and does no processing or regeneration of the traffic coming through it. Another type of hub is an active hub, which contains circuitry that can filter, amplify and control the traffic going through it. Hubs may also contain additional utilities, such as bridging, manageability, and repeaters. Active hubs are based on an extension of the network repeater.
It does this by accepting network traffic on its input side, and then amplifying the signal on its output, allowing it to travel farther. A hub is a multi-port repeater. Physically, it appears as a box with one input port and a number of output ports hat are typically wired to end-user workstation connections, although servers and other devices can be attached as well. Signals on any port are transmitted to all the other ports. Although a basic hub provides a way to organize cable wiring, it does not segment or organize network traffic in any way.
Hubs are used in the design and implementation of a coherent and easily managed network cabling system. In a typical design, a company may run cabling from a wall plate in each user’s cubicle to a central wiring closet on each floor of the building. These cables, known as station drops are each connected to a port on the wiring ub. The hubs on each floor are then connected to the network backbone, which runs from floor to floor in each wiring closet. This divides the network into logical and physical groupings that simplifies troubleshooting and network growth.
Because of the signal boosting performed by the hub, it can also extend the physical scope of the network. A recent innovation is the concept of the switching hub. A switching hub basically bridges the output as well as the input ports on the hub. With this arrangement, traffic from a port will not pass to the hub unless it needs to access a different port than it came in on. If it needs to pass across the hub to reach its destination, it only passes between the two ports it needs, and is isolated from the rest of the ports.
This cuts down unnecessary traffic on all network segments attached to the hub, improving the capacity and speed of the network. A bridge is used to interconnect two or more similar LANs or to divide a large network into smaller more manageable ones. Splitting of a large network with a bridge increases the efficiency of the network and reduces the chances of an overload. A bridge is able to increase ffectiveness of two connected networks because it only passes information is bound for the “far side” of the bridge if necessary. There are two types of bridges, simple and learning.
A simple bridge receives packets of information and retransmits them to all ports until that packet reaches the correct one. A learning bridge reads, stores, and learns the addresses of each computer on the network. The learning bridge then constructs a table to efficiently route packets to the correct port, without wasting resources sending each packet to every port. If a packet comes through the bridge intended for a estination not recorded on the bridging table, the bridge sends the packet out to all ports and records the accepting destination.
A repeater is a device that extends the length of transmission media over which network information is passed. A repeater accepts network input, amplifies the signal, and retransmits the information. Repeaters are especially useful when a network is cabled throughout a large building, over several floors. They are also able to filter out interference or distortion before retransmission, but are unable to operate efficiently when attempting to transfer huge amounts of information.