Networking Hardware
Hardware is the physical devices that are the elements of a network. Networking hardware includes computers, peripherals, interface cards and other equipment needed to perform data-processing and communications.
There are several basic components of the networking hardware:
File Servers
A file server is a very important component of most networks. A file server is a very fast computer with a large amount of RAM and storage space (hard drive), and a fast network interface card (NIC). This computer has a network operating system (NOS) and any other software applications and data files that need to be shared.
The primary function of the file server is to control communication of information between the nodes on a network. At the same time the file server oversees many different activities on the network: sending software applications to one workstation, receiving a database file from another workstation, and storing e-mail messages coming from the nodes engaged in communication. These responsibilities require a computer that can store a lot of information and share it very quickly.
For an efficient and productive performance a file server should have at least the following chatacteristics:
166 megahertz (MHz) or faster microprocessor (Pentium, PowerPC)
A fast hard drive with at least 9 gigabytes (GB) of storage
A RAID (Redundant Array of Inexpensive Disks) to preserve data after a disk casualty
A tape back-up unit (i.e. DAT, JAZ, Zip, or CD or DVD-RW drive)
Numerous expansion slots
Fast network interface card
At least 32 MB of RAM
Workstations
The computers connected to the file server on a network are called workstations. A workstation is a computer that is configured with a network interface card, networking software, and the appropriate cables. Workstations do not require a large capacity hard drives or any secondary storage devices because files can be stored on the file server.
Network Interface Cards (NICs)
The network interface card (NIC) has a function of providing a physical connection between the network and the computer workstation. Today most NICs are internal, that is the card is located inside ot the system unit, fitting into an expansion slot on the motherboard. However, some computers, such as Mac Classics, use external boxes which are attached to a serial port or a SCSI port. Laptop computers today have either a network interface card built-in or allow the card to slip into a PCMCIA slot.
Network interface cards play a very important role in determining the speed and performance of a network. The rule here is to use the fastest network card available for the type of workstation used.
There are three most common network interface connections:
Ethernet Cards
Ethernet cards may be either pre-installed or purchased separately from the computer. These cards contain conncections for either coaxial or twisted pair cables, or may have both. Some Ethernet cards also contain as AUI connector. This connector can be used to attach coaxial, twisted pair, or fiber optics cable to an Ethernet card. In this case, there is always an external transceiver attached to the workstation.
LocalTalk Connectors
LocalTalk is Apple's built-in solution for networking Macintosh computers. It utilizes a special adapter box and a cable that plugs into the printer port of a Macintosh. However, the disadvntage of LocalTalk is that it is slow compared to Ethernet. Most Ethernet connections operate at 10 megabits per second (Mbps). LocalTalk operates at only 230 kilobits per second (Kbps), which is equal to 0.23 Mbps.
Token Ring Cards
Token Ring network cards look similar to Ethernet cards. However, one of the differences is the type of connector on the back of the card. Token Ring cards have a nine pin DIN type connector, which attaches the card to the network cable.
Today Ethernet is recognized as the most popular type of connection.
Hubs and Switches
A hub or a switch is a concentrator - a device that provides a central connection point for cables from workstations, servers, and peripherals.
Hub
Hubs operate on the broadcating principle. When a workstation transmits a bit to the hub, the hub broadcasts the bit out of all ports, to all workstations attached to the hub. Based on the destination address each receiving workstation decides whether the information transmitted is intended for it or not. If it is not intended for a particular workstation, the information is discarded.
This type of communication creates congestion and latency on the network. If one workstation is transmitting at the time when another workstation is attempting to do the same, the second station has to wait, thus, creating latency. This becomes quite a noticeable problem if there is a large number of workstations on the network.
Broadcasting is very simple, and it makes hubs extremely inexpensive. However, due to the congestion and latency hubs can be used efficiently only on small networks.
Switch
Most switches today are active, that is they electrically amplify the signal as it moves from one device to another. Switches no longer broadcast network packets. They hold address information of computers and transmit directly to the correct location.
Switches:
Usually configured with 8, 12, or 24 RJ-45 ports
Often used in a star or star-wired ring topology
Sold with specialized software for port management
Usually installed in a standardized metal rack that also may store netmodems, bridges, or routers
May have built-in firewalls, routers, repeaters, and wireless transceivers
Repeaters
As the signal passes along a cable it loses its strength. To make sure that the signal reaches its destination it is often necessary to boost that signal. For this purpose a special device is used, called Repeater. The repeater electrically amplifies the signal it receives and re-broadcasts it.
Repeaters can be separate devices or they can be incorporated into a switch. Repeaters are used when the total length of the network cable exceeds the standards, which are set for the type of cable being used on the network.
Bridges
A bridge is a device that allows to segment a large network into two smaller, more efficient and manageable networks. A bridge can be used to connect an older wiring scheme with the newer network.
The function of a bridge is to monitor the information traffic on both sides of the network, so that it can send packets of information to the correct location. The bridge can inspect each message and broadcast it on the other side of the network.
The bridge manages the traffic to maintain optimum performance on both sides of the network. It keeps information flowing on both sides of the network, but it does not allow unnecessary traffic through.
Bridges may be used to connect different types of cabling, or physical topologies. However, they must be used between networks with the same protocol.
Routers
A router translates information from one network to another. A router is a "superintelligent" bridge. Routers select the best path to route a message, based on the destination address and origin. To prevent collisions of packets on the network the routers can re-direct the traffic. Capable of detecting the busiest sections of the network routers choose alternative paths for delivering messages.
While bridges know the addresses of all computers only on each side of the network, routers know the addresses of computers, bridges, and other routers on the entire network.
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