Computer NetworkZ

Computer Network

• Computer Network definition about connection of a lot of computers ( one computer with others computer ) so it can make data communication on others way, computer network means system in which computers are connected to share information and resources. The connection can be done as peer-to-peer or client/server.

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A computer network can be two computers connected:







A computer network can also consist of, and is usually made for, more than two computers:

The primary purpose of a computer network is to share resources:

• You can play a CD or DVD music from one computer while sitting on another computer
• You may have a computer with a CD / DVD writer or a backup system but the other computer doesn’t have it; In this case, you can burn CD's or make backups on a computer that has one of these but using data from a computer that doesn’t have a CD writer or a backup system

• You can place a CD with pictures on one computer and let other computers access those picture.
• You can create files and store them in one computer, then access those files from the other computers connected to it
• You also can connecting printer or scanner between one computer to others computer, and it hardware can use together, easy !
  

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Type of Computer Network divided by two, such as :

• Geographic, such as : (click to see the meaning of each )
  

• L A N ( Local Area Network )

• M A N ( Metropolitan Area Network )

• W A N ( Wide Area Network )

• Topology, such as Logical topology and Physical topology ( Point to point and Multipoint )

• Point to point divided to 3 type such as Bus topology, Ring topology, and Star topology

Bus topology

Benefits :

• economized the cable
• simple cable layout
• easy to develop

disadvantages :

• detection of errors are very small
• must have repeater for long distance
• if one client error, so the network cannot work
  

Ring topology
Benefits :

• economized the cable

disadvantages :

• easy to get errors
  
• networks development are stiff
  
• if one client error, so the network cannot work
  

Star topology

• Star topology is more benefit than Bus and Ring topology because all of the computers connect with a Hub/Switch so if one computer cannot work, the others computer can stay work. Others benefit, more flexible, easy to developing the network, easy to check the error problem.
• but star topology also have a lot of disadvantages, such as wasteful the cable, and need much money to build that. more errors in HUB system
  

Networking Equipments

Networking equipments are used to link a number of devices, such as computers, servers, workstations, printers, and scanners into a network (system) for the purpose of sharing resources. Networking of computer systems and other electronic devices has become a necessity for most working environments. A local area network (LAN) is a local computer network sharing the resources of a single processor or server within a relatively small geographic area. Most LANs are confined to a single building or group of buildings.

• NIC ( Network Interface Card )

NIC provides the hardware interface between a computer and a network. A NIC technically is network adapter hardware in the form factor of an add-in card such as a PCI or PCMCIA card.

Some NIC cards work with wired connections while others are wireless. Most NICs support either wired Ethernet or Wi-Fi wireless standards. Ethernet NICs plug into the system bus of the PC and include jacks for network cables, while WiFi NICs contain built-in transmitters / receivers (transceivers).

In new computers, many NICs are now pre-installed by the manufacturer. All NICs feature a speed rating such as 11 Mbps, 54 Mbps or 100 Mbps that suggest the general performance of the unit.

NIC also stands for Network Information Center. For example, the organization named "InterNIC" is a NIC that provides information to the general public on Internet domain names.

10 base 2, 10 base 5, and 10 baseT types of NIC

• H u b

hub is a small, simple, inexpensive device that joins multiple computers together. Many network hubs available today support the Ethernet standard. Other types including USB hubs also exist, but Ethernet is the type traditionally used in home networking.

To network a group of computers using an Ethernet hub, first connect an Ethernet cable into the unit, then connect the other end of the cable to each computer's NIC. All Ethernet hubs accept the RJ-45 connectors of standard Ethernet cables.

also varies. Four- and five-port Ethernet hubs are most common in home networks, but eight- and 16-port hubs can be found in some home and small office environments.

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• Repeater

Network repeaters regenerate incoming electrical, wireless or optical signals. With physical media like Ethernet or Wi-Fi, data transmissions can only span a limited distance before the quality of the signal degrades. Repeaters attempt to preserve signal integrity and extend the distance over which data can safely travel.

Actual network devices that serve as repeaters usually have some other name. Active hubs, for example, are repeaters. Active hubs are sometimes also called "multiport repeaters," but more commonly they are just "hubs." Other types of "passive hubs" are not repeaters. In Wi-Fi, access point function as repeaters only when operating in so-called "repeater mode."

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• Router

A computer network is a collection of interconnected computing devices that exchange data and share resources. A router connects computer networks having different lower hierarchy structures. The router transmits packet data through an optimal path established in connection with a routing table, as well as connects the received packet to another network or a target node of its own network.

An IP router using an optical switch fabric takes in internet protocol packets and routes them through an optical switch to various destination ports of the switch. The router stores a routing table therein, and checks the IP address of each packet transmitted from another node by referring to the routing table, to determine the next destination or node of the packet and sends out the packet.

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Cable tech

There are two types of cable such as cooper cable which use electromagnetic signal and optic fiber which use light energy

• Cooper cable divided by two types : T.P ( Twisted Pair ) and Coaxial cable

Twisted Pair

Twisted pair cables are so named because pairs of wires are twisted around one another. Each pair consists of two insulated copper wires twisted together. The wire pairs are twisted because it helps reduce crosstalk and noise susceptibility. High quality twisted pair cables have about 1 to 3 twists per inch. For best results, the twist rate should vary significantly between pairs in a cable.

Twisted pair cables are used with the following Ethernet physical layers: 10Base-T, 100Base-TX, 100Base-T2, 100Base-T4, and 1000Base-T. The following sections describe the various types of twisted pair cabling.

• There are two type of Twisted Pair cable : STP ( Shield Twisted Pair ), ScTP, and UTP ( Unshield Twisted Pair )
• UTP cable usually use by network configuration because more cheap than STP

UTP ( Unshield Twisted Pair )

As the name implies, "unshielded twisted pair" (UTP) cabling is twisted pair cabling that contains no shielding. For networking applications, the term UTP generally refers to the 100 ohm, Category 3, 4, & 5 cables specified in the TIA/EIA 568-A standard. Category 5e, 6, & 7 standards have also been proposed to support higher speed transmission. UTP cabling most commonly includes 4 pairs of wires enclosed in a common sheath. 10Base-T, 100Base-TX, and 100Base-T2 use only 2 of the twisted pairs, while 100Base-T4 and 1000Base-T require all 4 twisted pairs.

• There are seven category of Unshield Twisted Pair cable :

1. Category one for sound and for telephone cable
2. Category two have maximum data speed 4Mbps
3. Category three have maximum data speed 10Mbps
4. Category four have maximum data speed 20Mbps
5. Category five have maximum data speed 100Mbps
6. Category five e have maximum data speed 100Mbps ( Tuning of 5 )
7. Category six have maximum data speed 250Mbps
8. Category seven have maximum data speed 600Mbps

Connector for UTP Category 1 and 2 is Rj 11 and for category 3 , 7 is Rj 45



example of Rj 45 connector

Screened Twisted Pair (ScTP)

Screened Twisted Pair (ScTP) is 4-pair 100 ohm UTP, with a single foil or braided screen surrounding all four pairs in order to minimize EMI radiation and susceptibility to outside noise. Screened twisted pair is also called Foil Twisted Pair (FTP), or Screened UTP (sUTP). ScTP can be thought of as a shielded version of the Category 3, 4, & 5 UTP cables. It may be used in Ethernet applications in the same manner as the equivalent Category of UTP cabling.

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STP ( Shielded Twisted Pair )

"Shielded Twisted Pair" (STP) most often refers to the 150 ohm twisted pair cabling defined by the IBM Cabling System specifications for use with Token-Ring networks. The twisted pairs in 150 ohm STP are individually wrapped in a foil shield and enclosed in an overall outer braided wire shield. The shielding is designed to minimize EMI radiation and susceptibility to crosstalk.

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Coaxial Cabling

Coaxial cable is a type of communication transmission cable in which a solid center conductor is surrounded by an insulating spacer which in turn is surrounded by a tubular outer conductor (usually a braid, foil or both). The entire assembly is then covered with an insulating and protective outer layer. Coaxial cables have a wide bandwidth and are capable of carrying many data, voice, and video conversations simultaneously.

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The following sections describe the various types of coaxial cable

a.Thicknet

Thicknet is the 50-ohm "thick" (10mm) coaxial cable used with Ethernet 10Base5 networks. 10Base5 is the original Ethernet system that supports a 10 Mb/s transmission rate over a 500 meter maximum supported segment length.

b.Thinnet

Thinnet is the 50-ohm "thin" (5mm) coaxial cable used with Ethernet 10Base2 networks. 10Base2, also known as "Thin Ethernet", or "cheapernet", supports a 10 Mb/s transmission rate over a 185 meter maximum supported segment length.

c.CATV

CATV cabling is the 75 ohm coaxial cabling commonly known for its use in transmission of Cable TV signals, but is also used with Ethernet 10Broad36 networks. CATV stands for "community antenna television".

CATV cabling is used for "broadband" transmission as opposed to the "baseband" transmission used by all other Ethernet physical layers. A broadband cabling system supports transmission of multiple services over a single cable by dividing the bandwidth into separate frequencies, with each frequency assigned to a different service. This technique is used in cable TV transmission systems to transmit multiple channels over a single cable. Each channel uses a different frequency range. This capability can allow 10Broad36 share a single cable with other services such as vidio

d.Twinax

Twinax, or twinaxial, is a type of communication transmission cable consisting of two center conductors surrounded by an insulating spacer which in turn is surrounded by a tubular outer conductor (usually a braid, foil or both). The entire assembly is then covered with an insulating and protective outer layer. Twinax is constructed much like coaxial cable, execpt it has two center conductors instead of one. However, it is similar to twisted pair cabling in that it uses differential, or "balanced", transmission.

Fiber Optic Cabling

Fiber optic cabling is a technology where electrical signals are converted into optical signals, transmitted through a thin glass fiber, and re-converted into electrical signals. It is used as transmission medium for the following Ethernet media systems: FOIRL, 10Base-FL, 10Base-FB, 10Base-FP, 100Base-FX, 1000Base-LX, and 1000Base-SX.

Fiber optic cabling is constructed of three concentric layers: The "core" is the central region of an optical fiber through which light is transmitted. The "cladding" is the material in the middle layer. It has a lower index of refraction than the core which serves to confine the light to the core. An outer "protective layer", or "buffer", serves to protect the core and cladding from damage.

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The divided of Fiber Optic Cable :

a. Multi-Mode Fiber (MMF)

Multi-mode fiber allows many "modes", or paths, of light to propagate down the fiber optic path. The relatively large core of a multi-mode fiber allows good coupling from inexpensive LEDs light sources, and the use of inexpensive couplers and connectors. Multi-mode fiber typically has a core diameter of 50 to 100 microns.

Two types of multi-mode fiber exist with a refractive index that may be "graded" or "stepped". With graded index fiber the index of refraction of the core is lower toward the outside of the core and progressively increases toward the center of the core, thereby reducing modal dispersion of the signal. With stepped index fiber the core is of uniform refractive index with a sharp decrease in the index of refraction at the core-cladding interface. Stepped index multi-mode fibers generally have lower bandwidths than graded index multi-mode fibers.

The primary advantage of multi-mode fiber over twisted pair cabling is that it supports longer segment lengths. Multi-mode fiber can support segment lengths as long as 2000 meters for 10 and 100 Mbps Ethernet, and 550 meters for 1 Gbps Ethernet.

b. Single-Mode Fiber (SMF)

Single-mode fiber has a core diameter that is so small (on the order of 10 microns) that only a single mode of light is propagated. This eliminates the main limitation to bandwidth, modal dispersion. However, the small core of a single-mode fiber makes coupling light into the fiber more difficult, and thus expensive lasers must be used as light sources. The main limitation to the bandwidth of a single-mode fiber is material (chromatic) dispersion. Laser sources must also be used to attain high bandwidth, because LEDs emit a large range of frequencies, and thus material dispersion becomes significant.

Single-mode fiber is capable of supporting much longer segment lengths than multi-mode fiber. Segment lengths of 5000 meters and beyond are supported at all Ethernet data rates through 1 Gbps. However, single-mode fiber has the disadvantage of being significantly more expensive to deploy than multi-mode fiber.