Telecommunication and Networking by Syahrul Amin
Tuesday 27 March 2012
Monday 26 March 2012
Computer Network
Computer Network
A computer network is interconnection of various computer systems located at
different places. In computer network two or more computers are linked together
with a medium and data communication devices for the purpose of
communication data and sharing resources. The computer that provides
resources to other computers on a network is known as server. In the network
the individual computers, which access shared network resources, are known as
nodes.
Types of Networks
Local-Area Networks (LANs)
The computers are geographically close together (that is, in the same building).
Wide-Area Networks (WANs)
The computers are farther apart and are connected by telephone lines or
radio waves. The following characteristics are also used to
categorize different types of networks.
- Topology
The geometric arrangement of a computer system. Common topologies include bus, star, and ring.
- Protocol
The protocol defines a common set of rules and signals that computers on the network use to communicate. One of the most popular protocols for LANs is called Ethernet. Another popular LAN protocol for PCs is the IBM token-ring network.
- Architecture
Networks can be broadly classified as using either peer-to-peer or client/server architecture. Computers on a network are sometimes called nodes. Computers and devices that allocate resources for a network are called servers.
- Local Area Network (LAN)
LAN is a computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANS over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a wide-area network (WAN).
Communication and Networking
Data Communication
We all are acquainted with some sorts of communication in our day to day life.
For communication of information and messages we use telephone and postal
communication systems. Similarly data and information from one computer
system can be transmitted to other systems across geographical areas. Thus data
transmission is the movement of information using some standard methods.
These methods include electrical signals carried along a conductor, optical
signals along an optical fibers and electromagnetic areas.
Basic Elements of a Communication System
The following are the basic requirements for working of a communication
system.
1. The sender (source) who creates the message to be transmitted
2. A medium that carries the message
3. The receiver (sink) who receives the message
In data communication four basic terms are frequently used. They are:
Data : A collection of facts in raw forms that become information after processing.
Signals : Electric or electromagnetic encoding of data.
Signaling : Propagation of signals across a communication medium.
Transmission : Communication of data achieved by the processing of signals.
Communication and Networking
Data Communication
We all are acquainted with some sorts of communication in our day to day life.
For communication of information and messages we use telephone and postal
communication systems. Similarly data and information from one computer
system can be transmitted to other systems across geographical areas. Thus data
transmission is the movement of information using some standard methods.
These methods include electrical signals carried along a conductor, optical
signals along an optical fibers and electromagnetic areas.
Basic Elements of a Communication System
The following are the basic requirements for working of a communication
system.
1. The sender (source) who creates the message to be transmitted
2. A medium that carries the message
3. The receiver (sink) who receives the message
In data communication four basic terms are frequently used. They are:
Data : A collection of facts in raw forms that become information after processing.
Signals : Electric or electromagnetic encoding of data.
Signaling : Propagation of signals across a communication medium.
Transmission : Communication of data achieved by the processing of signals.
Data Transmission Modes
Data Transmission Modes
There are three ways for transmitting data from one point to another.
1. Simplex : In simplex mode the communication can take place in one
direction. The receiver receives the signal from the transmitting device.
In this mode the flow of information is Uni-directional. Hence it is rarely
used for data communication.
2. Half-duplex : In half-duplex mode the communication channel is used
in both directions, but only in one direction at a time. Thus a half-duplex
line can alternately send and receive data.
3. Full-duplex : In full duplex the communication channel is used in both
directions at the same time. Use of full-duplex line improves the
efficiency as the line turnaround time required in half-duplex arrangement
is eliminated. Example of this mode of transmission is the telephone
line.
Sunday 25 March 2012
Serial Communications
Most digital messages are vastly longer than just a few bits. Because it is neither practical nor economic to transfer all bits of a long message simultaneously, the message is broken into smaller parts and transmitted sequentially. Bit-serial transmission conveys a message one bit at a time through a channel. Each bit represents a part of the message. The individual bits are then reassembled at the destination to compose the message. In general, one channel will pass only one bit at a time. Thus, bit-serial transmission is necessary in data communications if only a single channel is available. Bit-serial transmission is normally just called serial transmission and is the chosen communications method in many computer peripherals.
Byte-serial transmission conveys eight bits at a time through eight parallel channels. Although the raw transfer rate is eight times faster than in bit-serial transmission, eight channels are needed, and the cost may be as much as eight times higher to transmit the message. When distances are short, it may nonetheless be both feasible and economic to use parallel channels in return for high data rates. The popular Centronics printer interface is a case where byte-serial transmission is used. As another example, it is common practice to use a 16-bit-wide data bus to transfer data between a microprocessor and memory chips; this provides the equivalent of 16 parallel channels. On the other hand, when communicating with a timesharing system over a modem, only a single channel is available, and bit-serial transmission is required. This figure illustrates these ideas:
The baud rate refers to the signalling rate at which data is sent through a channel and is measured in electrical transitions per second. In the EIA232 serial interface standard, one signal transition, at most, occurs per bit, and the baud rate and bit rate are identical. In this case, a rate of 9600 baud corresponds to a transfer of 9,600 data bits per second with a bit period of 104 microseconds (1/9600 sec.). If two electrical transitions were required for each bit, as is the case in non-return-to-zero coding, then at a rate of 9600 baud, only 4800 bits per second could be conveyed. The channel efficiency is the number of bits of useful information passed through the channel per second. It does not include framing, formatting, and error detecting bits that may be added to the information bits before a message is transmitted, and will always be less than one.
The data rate of a channel is often specified by its bit rate (often thought erroneously to be the same as baud rate). However, an equivalent measure channel capacity is bandwidth. In general, the maximum data rate a channel can support is directly proportional to the channel's bandwidth and inversely proportional to the channel's noise level.
A communications protocol is an agreed-upon convention that defines the order and meaning of bits in a serial transmission. It may also specify a procedure for exchanging messages. A protocol will define how many data bits compose a message unit, the framing and formatting bits, any error-detecting bits that may be added, and other information that governs control of the communications hardware. Channel efficiency is determined by the protocol design rather than by digital hardware considerations. Note that there is a tradeoff between channel efficiency and reliability - protocols that provide greater immunity to noise by adding error-detecting and -correcting codes must necessarily become less efficient.
Byte-serial transmission conveys eight bits at a time through eight parallel channels. Although the raw transfer rate is eight times faster than in bit-serial transmission, eight channels are needed, and the cost may be as much as eight times higher to transmit the message. When distances are short, it may nonetheless be both feasible and economic to use parallel channels in return for high data rates. The popular Centronics printer interface is a case where byte-serial transmission is used. As another example, it is common practice to use a 16-bit-wide data bus to transfer data between a microprocessor and memory chips; this provides the equivalent of 16 parallel channels. On the other hand, when communicating with a timesharing system over a modem, only a single channel is available, and bit-serial transmission is required. This figure illustrates these ideas:
The baud rate refers to the signalling rate at which data is sent through a channel and is measured in electrical transitions per second. In the EIA232 serial interface standard, one signal transition, at most, occurs per bit, and the baud rate and bit rate are identical. In this case, a rate of 9600 baud corresponds to a transfer of 9,600 data bits per second with a bit period of 104 microseconds (1/9600 sec.). If two electrical transitions were required for each bit, as is the case in non-return-to-zero coding, then at a rate of 9600 baud, only 4800 bits per second could be conveyed. The channel efficiency is the number of bits of useful information passed through the channel per second. It does not include framing, formatting, and error detecting bits that may be added to the information bits before a message is transmitted, and will always be less than one.
The data rate of a channel is often specified by its bit rate (often thought erroneously to be the same as baud rate). However, an equivalent measure channel capacity is bandwidth. In general, the maximum data rate a channel can support is directly proportional to the channel's bandwidth and inversely proportional to the channel's noise level.
A communications protocol is an agreed-upon convention that defines the order and meaning of bits in a serial transmission. It may also specify a procedure for exchanging messages. A protocol will define how many data bits compose a message unit, the framing and formatting bits, any error-detecting bits that may be added, and other information that governs control of the communications hardware. Channel efficiency is determined by the protocol design rather than by digital hardware considerations. Note that there is a tradeoff between channel efficiency and reliability - protocols that provide greater immunity to noise by adding error-detecting and -correcting codes must necessarily become less efficient.
Communications Channels
A communications channel is a pathway over which information can be conveyed. It may be defined by a physical wire that connects communicating devices, or by a radio, laser, or other radiated energy source that has no obvious physical presence. Information sent through a communications channel has a source from which the information originates, and a destination to which the information is delivered. Although information originates from a single source, there may be more than one destination, depending upon how many receive stations are linked to the channel and how much energy the transmitted signal possesses.
In a digital communications channel, the information is represented by individual data bits, which may be encapsulated into multibit message units. A byte, which consists of eight bits, is an example of a message unit that may be conveyed through a digital communications channel. A collection of bytes may itself be grouped into a frame or other higher-level message unit. Such multiple levels of encapsulation facilitate the handling of messages in a complex data communications network.
Any communications channel has a direction associated with it:
The message source is the transmitter, and the destination is the receiver. A channel whose direction of transmission is unchanging is referred to as a simplex channel. For example, a radio station is a simplex channel because it always transmits the signal to its listeners and never allows them to transmit back.
A half-duplex channel is a single physical channel in which the direction may be reversed. Messages may flow in two directions, but never at the same time, in a half-duplex system. In a telephone call, one party speaks while the other listens. After a pause, the other party speaks and the first party listens. Speaking simultaneously results in garbled sound that cannot be understood.
A full-duplex channel allows simultaneous message exchange in both directions. It really consists of two simplex channels, a forward channel and a reverse channel, linking the same points. The transmission rate of the reverse channel may be slower if it is used only for flow control of the forward channel.
In a digital communications channel, the information is represented by individual data bits, which may be encapsulated into multibit message units. A byte, which consists of eight bits, is an example of a message unit that may be conveyed through a digital communications channel. A collection of bytes may itself be grouped into a frame or other higher-level message unit. Such multiple levels of encapsulation facilitate the handling of messages in a complex data communications network.
Any communications channel has a direction associated with it:
The message source is the transmitter, and the destination is the receiver. A channel whose direction of transmission is unchanging is referred to as a simplex channel. For example, a radio station is a simplex channel because it always transmits the signal to its listeners and never allows them to transmit back.
A half-duplex channel is a single physical channel in which the direction may be reversed. Messages may flow in two directions, but never at the same time, in a half-duplex system. In a telephone call, one party speaks while the other listens. After a pause, the other party speaks and the first party listens. Speaking simultaneously results in garbled sound that cannot be understood.
A full-duplex channel allows simultaneous message exchange in both directions. It really consists of two simplex channels, a forward channel and a reverse channel, linking the same points. The transmission rate of the reverse channel may be slower if it is used only for flow control of the forward channel.
What is Data Communications?
The distance over which data moves within a computer may vary from a few thousandths of an inch, as is the case within a single IC chip, to as much as several feet along the backplane of the main circuit board. Over such small distances, digital data may be transmitted as direct, two-level electrical signals over simple copper conductors. Except for the fastest computers, circuit designers are not very concerned about the shape of the conductor or the analog characteristics of signal transmission.
Frequently, however, data must be sent beyond the local circuitry that constitutes a computer. In many cases, the distances involved may be enormous. Unfortunately, as the distance between the source of a message and its destination increases, accurate transmission becomes increasingly difficult. This results from the electrical distortion of signals traveling through long conductors, and from noise added to the signal as it propagates through a transmission medium. Although some precautions must be taken for data exchange within a computer, the biggest problems occur when data is transferred to devices outside the computer's circuitry. In this case, distortion and noise can become so severe that information is lost.
Data Communications concerns the transmission of digital messages to devices external to the message source. "External" devices are generally thought of as being independently powered circuitry that exists beyond the chassis of a computer or other digital message source. As a rule, the maximum permissible transmission rate of a message is directly proportional to signal power, and inversely proportional to channel noise. It is the aim of any communications system to provide the highest possible transmission rate at the lowest possible power and with the least possible noise.
Frequently, however, data must be sent beyond the local circuitry that constitutes a computer. In many cases, the distances involved may be enormous. Unfortunately, as the distance between the source of a message and its destination increases, accurate transmission becomes increasingly difficult. This results from the electrical distortion of signals traveling through long conductors, and from noise added to the signal as it propagates through a transmission medium. Although some precautions must be taken for data exchange within a computer, the biggest problems occur when data is transferred to devices outside the computer's circuitry. In this case, distortion and noise can become so severe that information is lost.
Data Communications concerns the transmission of digital messages to devices external to the message source. "External" devices are generally thought of as being independently powered circuitry that exists beyond the chassis of a computer or other digital message source. As a rule, the maximum permissible transmission rate of a message is directly proportional to signal power, and inversely proportional to channel noise. It is the aim of any communications system to provide the highest possible transmission rate at the lowest possible power and with the least possible noise.
apa itu network??
Sebelum kita pergi lebih jauh mengenai network, saya rasa anda patut tahu terlebih dahulu maksud network komputer dan klasifikasinya.
Apa itu network komputer?
Network komputer membawa maksud penyambungan dua buah komputer atau lebih atau kumpulan rangkaian komputer.Ia terbahagi kepada beberapa jenis sambungan seperti WAN,LAN,Wireless dan lain - lain.
Apa itu LAN?
LAN adalah Local Area Network atau jaringan komputer dalan suatu lingkupan(area) tertentu iaitu beberapa komputer yang saling terhubung satu sama lain baik melalui kabel taupun tidak(wireless; ciri khas:adanya hotspot) dengan tujuan saling berhububung resource(sumber daya) baik sharing file,printer mahupun sambungan internet.Untuk LAN biasa hanya terbatas pada satu tempat saja..Misalnya jaringan dibilik kita.
Apa itu WAN ?
WAN adalah Wide Area Network iaitu sejenis LAN tapi dengan maksud yang lebih luas.Boleh melintasi gedung,kota dsb..WAN juga dapat menggabungkan beberapa LAN..
Apa itu network komputer?
Network komputer membawa maksud penyambungan dua buah komputer atau lebih atau kumpulan rangkaian komputer.Ia terbahagi kepada beberapa jenis sambungan seperti WAN,LAN,Wireless dan lain - lain.
Apa itu LAN?
LAN adalah Local Area Network atau jaringan komputer dalan suatu lingkupan(area) tertentu iaitu beberapa komputer yang saling terhubung satu sama lain baik melalui kabel taupun tidak(wireless; ciri khas:adanya hotspot) dengan tujuan saling berhububung resource(sumber daya) baik sharing file,printer mahupun sambungan internet.Untuk LAN biasa hanya terbatas pada satu tempat saja..Misalnya jaringan dibilik kita.
Apa itu WAN ?
WAN adalah Wide Area Network iaitu sejenis LAN tapi dengan maksud yang lebih luas.Boleh melintasi gedung,kota dsb..WAN juga dapat menggabungkan beberapa LAN..
Sunday 18 March 2012
Wednesday 7 March 2012
cara nak tukar alamat email
cara nak tukar alamat email
Korang tau kan google dah nak tutop blog yang sign in dengan alamat email selain dari gmail.
So ape perasaan korang takot, kecut n ape2 je.
Hahaha
ni aku dah tunjukkn cara2 nak tukar alamat email, tapi aku pun tak tukar lagi,
coz aku gune enpon je nak online ni.
Tapi kalau nak daftar kena pakai komputer.
So kalau korang masih tak tahu cara nak tukar alamat email boleh la korang bace kat bawah ni.
1.masuk ke google
2.pergi ke gmail
3.pas tu tekan daftar
4.isi form tu kasi abis dan tekan daftar
5.dah siap!! log in ke blogger
6.pergi ke dashboard
7.pergi ke my account
8.cari Personal Settings
Security
9.pas tu tekan change email
10.pas tu teros masukkan alamat email google yang baru dibuat tadi
11.terus tekan save
ok siap.
Kalau boleh korang sebarkan lah menda2 ni.
Korang tau kan google dah nak tutop blog yang sign in dengan alamat email selain dari gmail.
So ape perasaan korang takot, kecut n ape2 je.
Hahaha
ni aku dah tunjukkn cara2 nak tukar alamat email, tapi aku pun tak tukar lagi,
coz aku gune enpon je nak online ni.
Tapi kalau nak daftar kena pakai komputer.
So kalau korang masih tak tahu cara nak tukar alamat email boleh la korang bace kat bawah ni.
1.masuk ke google
2.pergi ke gmail
3.pas tu tekan daftar
4.isi form tu kasi abis dan tekan daftar
5.dah siap!! log in ke blogger
6.pergi ke dashboard
7.pergi ke my account
8.cari Personal Settings
Security
9.pas tu tekan change email
10.pas tu teros masukkan alamat email google yang baru dibuat tadi
11.terus tekan save
ok siap.
Kalau boleh korang sebarkan lah menda2 ni.
Tuesday 6 March 2012
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