Computer Network

                                              WEEK 4

 Computer Network

It is simply a group of interconnected computers.Two or more computers are connected via hardware or software, and able to communicate with each other.

The computers of a network may be located nearby to each other or at different geographic locations.Example of a computer network:

the Internet, ATM, school network, e-banking, home network, etc.

well the computer network is quit import we use it in our everyday routines you know! ressources sharing information sharing and ofcourse emailing.

now let see what opponents that are required to computer network.first and first Communication Media,Interconnecting Devices,Computers,Applications and finally Networking Software.

Every computer Networking must have these three concepts which are Topology(the physical layout of the network).Protocol (the rules in data communication)and

Architecture(how the hardware and software are integrated to form a working.)

A computer network involves communicating data between computers.Three elements at least must exist:

Sender,medium and receiver

we've also learned some characteristics data  transmission,the first one is analog  transmission the data are transmitted in form of continuous waves transmitted over a medium at a certain frequency rage,

the rate of transmission is called bandwitch. The other sort of  transmission is Digital transmission: sends data in the form of bits.sorted by signal.

ordered by bits there is serial and parallel;series one bit is sent after another,but parallel all bit are sent at once a long multiple paths.

again Bandwidth is the range that a medium can correctly transmit data.The rate at which the signal changes is known as Baud

Some type of link through which the data can be transmitted or transferred from one computer to another. To send data through the channel requires some type of transmission media, which may be either physical or wireless.

Computers share access to common network medium that carries signals from one computer to another. Medium may be physical cable, such as twisted pair, coaxial, or fiber-optic. Medium may also be wireless. Physical interface to medium is usually network interface card (NIC) or network adapter. Kind of medium dictates type of connector and limits number and type of devices as well as distance a single LAN can span

Twisted-pair cable – consists of two independently insulated wires twisted around each other (least expensive type of cable—the kind that is used in many telephone systems)

Coaxial cable – consists of an insulated center wire grounded by a shield of braided wire (the primary type of cabling used by the cable television industry;  it is more expensive than twisted pair)

Fiber-optic cable – contains hundreds of clear fiberglass or plastic fibers (threads) (made from thin, flexible glass tubing; bandwidth is greater, so it can carry more data; it is lighter than metal wires and is less susceptible to interference; it is fragile and expensive)

ISDN line – a special digital telephone line that transmits and receives information at very high speeds

                                                Wireless Media

Also known as unguided medium.

Microwave system – transmits data via high-frequency radio signals through the atmosphere.Satellite system – receive transmitted signals, amplify them, and then transmit the signals to the appropriate locations Cellular technology – uses antennae resembling telephone towers to pick up radio signals within a specific area (cell)Infrared technology – transmits data as infrared light waves from one device to another, providing wireless links between PCs and peripherals

Digital Communication

Communication has changed radically in today’s digital age and our lifestyle.Today, we are talking about digital communication, digital entertainment, digital mobility and so forth.It’s already happening accessing home computer from our cell phone. This is the era of digital telephony.

Challenging question J :

Can you describe the communication medium involved in digital telephony?

                                       Wireless Networking : Wi-Fi

•Wi-Fi is an abbreviation for Wireless Fidelity and a catch all phrase for the several different standards and recommendations that comprise wireless networking. 

–IEEE 802.11.b –2.4GHz – 11Mbps

–IEEE 802.11.a – 5GHz – 54 Mbps

–IEEE 802.11g – 2.4Ghz – Hybrid 11/54Mbps 

•Wi-Fi enables the user to deploy a computer network without needing to run cable throughout the facility.

•Microwave ovens, cordless phones, medical and scientific equipment, as well as Bluetooth devices, all work within the 2.4 GHz frequency band.

  

Application-Any application currently used on a traditional wired network can be used on a                                  wireless network. New applications may be available or can be developped to 
                                 take advantage of wireless, such as Wireless PDA access to a card catalog.

However, Wi-Fi has limitations such as:

–The effective coverage is 300-1400ft. from access point

–Structural interference

–Interference from other devices such as cordless phones.

this the end of this week, andIi guess you are enjoning this lesson  i ll see you nest week chao!