(2A) Communication methods and speeds in real world situations Communication methods including: LAN / WAN basic communication types including: simplex half-duplex duplex. point-to-point communication handshakes

LAN A LAN covers a small area such as one site or building, eg a school or a college.

WAN A WAN covers a large geographical area. Most WANs are made from several LANs connected together

What is Data Communication? Data communication refers to the exchange of data between a source and a receiver. Data communication is said to be local if communicating devices are in the same building or a similarly restricted geographical area. The meanings of source and receiver are very simple. The device that transmits the data is known as source and the device that receives the transmitted data is known as receiver. Data communication aims at the transfer of data and maintenance of the data during the process but not the actual generation of the information at the source and receiver.

Components of data communication system 1. Message: It is the information or data to be communicated. It can consist of text, numbers, pictures, sound or video or any combination of these. 2. Sender: It is the device/computer that generates and sends that message. 3. Receiver: It is the device or computer that receives the message. The location of receiver computer is generally different from the sender computer. The distance between sender and receiver depends upon the types of network used in between. 4. Medium: It is the channel or physical path through which the message is carried from sender to the receiver. The medium can be wired like twisted pair wire, coaxial cable, fiber-optic cable or wireless like laser, radio waves, and microwaves. 5. Protocol: It is a set of rules that govern the communication between the devices. Both sender and receiver follow same protocols to communicate with each other.

Protocols In networking a Protocol refers to a set of rules that are used to agree how data should be transferred. Protocols are often described in an industry or international standard. The TCP/IP Internet protocols, a common example, consist of: Transmission Control Protocol (TCP), which uses a set of rules to exchange messages with other Internet points at the information packet level Internet Protocol (IP), which uses a set of rules to send and receive messages at the Internet address level Additional protocols that include the Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP), each with defined sets of rules to use with corresponding programs elsewhere on the Internet There are many other Internet protocols, such as the Border Gateway Protocol (BGP) and the Dynamic Host Configuration Protocol (DHCP).

A protocol performs the following functions: 1. Data sequencing. It refers to breaking a long message into smaller packets of fixed size. Data sequencing rules define the method of numbering packets to detect loss or duplication of packets, and to correctly identify packets, which belong to same message. 2. Data routing. Data routing defines the most efficient path between the source and destination. 3. Data formatting. Data formatting rules define which group of bits or characters within packet constitute data, control, addressing, or other information. 4. Flow control. A communication protocol also prevents a fast sender from overwhelming a slow receiver. It ensures resource sharing and protection against traffic congestion by regulating the flow of data on communication lines. 5. Error control. These rules are designed to detect errors in messages and to ensure transmission of correct messages. The most common method is to retransmit erroneous message block. In such a case, a block having error is discarded by the receiver and is retransmitted by the sender. 6. Precedence and order of transmission. These rules ensure that all the nodes get a chance to use the communication lines and other resources of the network based on the priorities assigned to them. 7. Connection establishment and termination. These rules define how connections are established, maintained and terminated when two nodes of a network want to communicate with each other. 8. Data security. Providing data security and privacy is also built into most communication software packages. It prevents access of data by unauthorized users.

Point to Point In telecommunications, a point-to-point connection refers to a communications connection between two nodes or endpoints. An example is a telephone call, in which one telephone is connected with one other, and what is said by one caller can only be heard by the other. This is contrasted with a point-to-multipoint or broadcast connection, in which many nodes can receive information transmitted by one node. Other examples of point-to-point communications links are leased lines, microwave relay links, and two way radio.

Handshakes It is usually a process that takes place when a computer is about to communicate with a foreign device to establish rules for communication. When a computer communicates with another device like a modem or a printer it needs to handshake with it to establish a connection. Much like humans greet each other by a handshake to establish a connection. Handshaking may be used to negotiate parameters that are acceptable to equipment and systems at both ends of the communication channel, including, but not limited to, information transfer rate, coding alphabet, parity, interrupt procedure and other protocol or hardware features. Handshaking makes it possible to connect different systems or equipment over a communication channel without the need for human intervention to set parameters. One classic example of handshaking is that of modems, which typically negotiate communication parameters for a brief period when connection is first established, and thereafter use those parameters to provide optimal information transfer over the channel as a function of its quality and capacity. A typical handshaking process follows the following steps: Sending device checks if receiving device is connected and ready to receive. Sending device informs the receiving device it is sending. Receiving device confirms that it has received. Receiver indicates that it is ready to receive again.

What Are the Types of Data Communication? Data communication is the transmission of digital messages to external devices. If you look around your house, you will see many examples of data communication at work. Your cable system, your home phone and even your computer all work based on varying types of data transfer. The process of transmitting a message occurs millions of time a day without any of us being aware of it. Today's recent data transfer methods include many complex concepts, but we can still break down the process to a few basic types.

Simplex A simplex communication system sends a message in only one direction. The message source works as the transmitter. It sends the message over the data channel to the receiver. The receiver is the destination of the message. Examples of simplex data communication include radio stations and TV broadcasts. With the simplex channel, there is no ability by the receiver to respond to the message. For example, a radio station plays a song on your car radio. The data transferred is the song. You do not have the opportunity to send a message back via your car radio to the station.

Half Duplex A half-duplex data communication system provides messages in both directions but only allows transfer in one direction at a time. Once a party begins sending a transmission, the receiver must wait until the signal stops before responding. If the two data transfers attempt to send at the same time, they both fail. For instance, if you talk on a CB radio, you press a button and speak. If the receiver attempts to press the button and speak at the same time, neither one of you hear either message. The system is not capable of sending both ways simultaneously.

Full Duplex A full duplex is a communication that works both ways at the same time. Essentially, full duplex data communication is a set of two simplex channels, one works as a forward channel and the other as a reserve channel. The two channels link together at some point. An example of a full duplex communication system is a landline telephone. When talking on a telephone, both parties have the ability to speak at the same time. The data, carried both ways through the telephone line, runs simultaneously.