minggu kelima : network topology

Network topology is the layout pattern of interconnections of the various elements (links, nodes, etc.) of a computer or biological network.Network topologies may be physical or logical.

There are several basic types of topology in networks:

(1) BUS TOPOLOGY

A linear bus topology consists of a main run of cable with a terminator at each end. All nodes (file server, workstations, and peripherals) are connected to the linear cable.Ethernet and LocalTalk networks use a linear bus topology.The bus cable carries the transmitted message along the cable. As the message arrives at each workstation, the workstation computer checks the destination address contained in the message to see if it matches it's own. If the address does not match, the workstation does nothing more. If the workstation address matches that contained in the message, the workstation processes the message. The message is transmitted along the cable and is visible to all computers connected to that cable.

Advantages of a Linear Bus Topology

• Easy to connect a computer or peripheral to a linear bus.
• Requires less cable length than a star topology.

Disadvantages

• Entire network shuts down if there is a break in the main cable.
• A faulty cable or workstation will take the entire LAN down
• terminators are required at both ends of the backbone cable.
• Difficult to identify the problem if the entire network shuts down.
• Not meant to be used as a stand-alone solution in a large building.

(2) STAR TOPOLOGY

A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub or concentrator. Data on a star network passes through the hub or concentrator before continuing to its destination. The hub or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow.This configuration is common with twisted pair cable; however, it can also be used with coaxial cable or fiber optic cable.The protocols used with star configurations are usually Ethernet or LocalTalk.

Advantages

• Easy to install, and wire.
• Easy to add new workstations
• No disruptions to the network when connecting or removing devices.
• Any non-centralised failure will have very little effect on the network
• Easy to detect faults and to remove parts.
• Centralized control Centralized network/hub monitoring

Disadvantages

• Requires more cable length than a linear topology.
• If the hub or concentrator fails, nodes attached are disabled.
• More expensive than linear bus topologies because of the cost of the concentrators.

(3) STAR-WIRED

A star-wired topology may appear (externally) to be the same as a star topology. Internally, the MAU (multistation access unit) of a star-wired ring contains wiring that allows information to pass from one device to another in a circle or ring. The Token Ring protocol uses a star-wired topology.

(4) TREE TOPOLOGY

A tree topology combines characteristics of linear bus and star topologies.It consists of groups of star-configured workstations connected to a linear bus backbone cable. Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.

Advantage

• Point-to-point wiring for individual segments.

Disadvantages

• Overall length of each segment is limited by the type of cabling used.
• if the backbone line breaks, the entire segment goes down.
• More difficult to configure and wire than other topologies.

(5) ETHERNET

      Ethernet is the most widely-installed local area network ( LAN) technology. Specified in a standard, IEEE 802.3, Ethernet was originally developed by Xerox from an earlier specification called Alohanet (for the Palo Alto Research Center Aloha network) and then developed further by Xerox, DEC, and Intel. An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires. Ethernet is also used in wireless

ethernet cables

(6) LOCALTALK

     

    LocalTalk is a particular implementation of the physical layer of the AppleTalk networking system from Apple Computer. LocalTalk specifies a system of shielded twisted pair cabling, plugged into self-terminating transceivers, running at a rate of 230.4 kbit/s.CSMA/CA was implemented as a random multiple access method.

minggu 4:networking

what is computer networking ??
-connecting a computer with other computer or other devices to enable them to communicate with each other .
It can be :
 -Computer devices/equipment
–transmission media to send/control data/signals,
–Communication devices to transmit/send data from sources to destinations
–softwares


There are several types of this LAN based geographic :
1.LAN-local area network
2.MAN-Metropolitan area network
3.WAN-Wide area network


And then we go to network component .We can categorise it into 5 component . 


1.Terminals
-Refers to data sources and destination .
examples-workstation,personal computer,terminals,automatic teller machine


2.Transmission Media
-used to transmit data in a networked enviroment
-transmit pulse through a medium
-there are 2 types of it, bounded and unbounded


Bounded-twisted pair wire,co-axial cable,fiber optic cable
Unbounded-AM and FM radio,TV broadcasting,Microwave signal


3.Network Electronic Devices
-Devices that control data transmission from sources to destination
-Also act as interface between different transmission media


Examples-Bridges,Hub,Routers,Multiplexers,Gateway,Private Branch


4.Network
-a network operating system (NOS)
-control data transmission,a network & it message,traffic and queues .
-provide certain administrative function,including security


5.Network Architecture Standards
-Standard to enable devices made by different companies to work/communicate with each other 
-Blueprint of standard for a network consisting of item such as choices of media,media interface,encoding method and transmission protocol.
-Needed to ensure interoperability between various devices and equipment made by different vendors .   

minggu ketiga:data communication

Data communication ? 
-Data Communications is the transfer of data or information between a source and a receiver. The source transmits the data and the receiver receives it. The actual generation of the information is not part of Data Communications nor is the resulting action of the information at the receiver. Data Communication is interested in the transfer of data, the method of transfer and the preservation of the data during the transfer process.
Modem ?
-Modem, device that converts between analog and digital signals. Digital signals, which are used by computers, are made up of separate units, usually represented by a series of 1's and 0's. Analog signals vary continuously; an example of an analog signal is a sound wave.

Modems are often used to enable computers to communicate with each other across telephone lines. A modem converts the digital signals of the sending computer to analog signals that can be transmitted through telephone lines. When the signal reaches its destination, another modem reconstructs the original digital signal, which is processed by the receiving computer.

To convert a digital signal to an analog one, the modem generates a carrier wave and modulates it according to the digital signal. The process of receiving the analog signal and converting it back to a digital signal is called demodulation. The word "modem" is a contraction of its two basic functions: modulation and demodulation.

Amplitude , Period and Frequency 

-Amplitude (A): how high the peaks are or how low the troughs are, in meters.

The displacement is how far the wave vibrates / oscillates about its equilibrium (center) position.

Amplitude is correlated with the total energy of the system in periodic motion. Larger amplitude = greater energy.

Period (T): the time it takes for one cycle, in seconds.

Frequency (f): the rate, or how many cycles per second, in Hertz (cycles per second)

Coaxial Cable

-It consists of 2 conductors. The inner conductor is held inside an insulator with the other conductor woven around it providing a shield. An insulating protective coating called a jacket covers the outer conductor.

The outer shield protects the inner conductor from outside electrical signals. The distance between the outer conductor (shield) and inner conductor plus the type of material used for insulating the inner conductor determine the cable properties or impedance. Typical impedances for coaxial cables are 75 ohms for Cable TV, 50 ohms for Ethernet Thinnet and Thicknet. The excellent control of the impedance characteristics of the cable allow higher data rates to be transferred than Twisted Pair cable.

Optical Fibre

- consists of thin glass fibres that can carry information at frequencies in the visible light spectrum and beyond. The typical optical fibre consists of a very narrow strand of glass called the Core. Around the Core is a concentric layer of glass called the Cladding. A typical Core diameter is 62.5 microns (1 micron = 10-6 meters). Typically Cladding has a diameter of 125 microns. Coating the cladding is a protective coating consisting of plastic, it is called the Jacket.

Data Transmission

-The physical connection determines how many bits (1's or 0's) can be transmitted at a single instance of time. If only 1 bit of information can be transmitted over the data transmission medium at a time then it is considered a Serial Communication.

If more than 1 bit of information is transmitted over the data transmission medium at a time then it is considered a Parallel Communication. 

Data Flow

Data flow is the flow of data between 2 points. The direction of the data flow can be described as:

Simplex: data flows in only one direction on the data communication line (medium). Examples are Radio and Television broadcasts. They go from the TV station to your home television.

Half-Duplex: data flows in both directions but only one direction at a time on the data communication line. Ex. Conversation on walkie-talkies is a half-duplex data flow. Each person takes turns talking. If both talk at once - nothing occurs!

Full-Duplex: data flows in both directions simultaneously. Modems are configured to flow data in both directions. 

Minggu kedua:Web Searching

example of web browser

A web browser can be defined as an application software or programme designed to enable users to access,retrieve and view documents and other resources on the internet .the example of web browser is like google chrome,mozilla firefox and safari.

Search engine

search engine is designed to search for information on the World Wide Web .The information may consist of web pages,images,information and other types of files

search engine

Skill to know

There are some skill that we had to know in term of improving ourselves as a internet user .when we open files,it will be on certain format such as pdf,html,jpg,gif,txt and so on .We must know the uses of certain button in the web such as refresh,back and forward . The knowledge of bookmarking,clear cache,clear history,clear URL and setting default page must be know by the user too,to make sure that we can maximise the usage of the internet .

Minggu pertama:telekomunikasi dan rangkaian

model shannnon weaver

oke .telekomunikasi ? di mana asal perkataan ini ?  kita selalu sebutnya di dalam kehidupan seharian,tapi tahukah anda di mana asalnya perkataan ini ? telekomunikasi berasal dari perkataan Perancis " télécommunication" .Ianya ialah hasil gabungan dari perkataan greek iaitu tele yang bermaksud jauh dan juga perkataan latin communicare iaitu berkongsi .Perkataan Perancis Telecommunication pertama kali digunakan pada 1904 oleh seorang jurutera yang juga seorang novelis Perancis yang bernama Eduard Estaunie .Manakala untuk rangkaian pula,ianya bermaksud penyambungan antara dua buah komputer atau lebih .Jadi dapat dirumuskan,dalam telekomunikasi dan rangkaian ni ianya bertujuan untuk macam mana kita nak berhubungan dengan orang lain dan mendalami dengan lebih mengenai telekomunikasi ini . oke ini antara model komunikasi yang dapat saya berikan .. 






Terdapat 6 elemen utama di dalam komputer dan teknologi komunikasi ni .
1)People
2)Procedure
3)Data / Information
4)Hardware
5)Software
6)Communication / connectivity


-keenam-enam elemen ni sangat lah penting dan ketiadaan salah satu darinya akan besar mempengaruhi kepada struktur komputer dan teknologi komunikasi ini .

kene aktif balik la blog saya nmpknye :)

fuhhh fuhhhh .berhabuk bai .bape tahun da tak bukak ni .tah la . haha .nway,dalam sem 2 ni,ade satu subjek ,iaitu telecommunication and networking dan salah satu dari assignment yang diberi kepada kami ialah,wujudkan blog atau develop blog kami ini supaya ianya mempunyai unsur2 T&N ni dan mempunyai summary ringkas dari ape yg kami dpat week by week. .jadi,baiklah ,saya akn cuba sedaya upaya merajinkan diri ini untuk mengupdate blog sy ni .hehe .oke,jumpe ag nanti .kbai !

harder faster better stronger

rajin plak nak post 2 entry skali ni .dlu kemaen malas .haha ,da alang2 kan .oke ,kali ni aku nak cite pasal weight management . firstly ,syukur alhamdulilah , lepas setahun lbey aku usaha , usaha tu , tak makan nasi sebulan , pumping setiap hari ,sit up ,squat jump ,skipping ,jogging , cycling n macam2 lagi la yang aku da cube . . akhirnye ,dpat gak feed back camni 'eh ko da kurus , da kurus la ko bro , bro ko maen gym ke ? ,asal laen muke ko skrang ? ' lbey kurang camtu la .pastu aku test la baju kan ,eh btol la , size M , S pon da lepas . haha .alhamdulilah . byk sebab nye aku nak kurus ni ,antaranye ,sebab cinta aku yg amat teramat kat dye ni . dye ni ? ragbiiii .hehe .aku tak nak awek pon takpe , asal aku ade ragbi  .haha .statement ni wat masa ni je eh .ahaha .oke , aku nak fitkan badan aku ni ,so aku bole jadi utility player , n chance utk maen ke peringkat tertinggi tu makin tinggi la kot kan ? sebab impian saya sgt la tggi ,even orang ckap ragbi ni takde future ,tapi takpe , i have my own plan ,dgn parent pon da paham n da sokong kan .thanx mama n papa .  :) . saya akan terus mengfitkan badan saya ni , bagi nampak berketul sikit .hehe .doakan saya guys ,thanx a lot . so ,jumpe ag .insyAllah . daa