Data Communication Lecture One PDF

DATA COMMUNICATION BY: DR. P. KUDJO INTRODUCTION TO DATA COMMUNICATION  Course Contents/Learning Objectives  Concept of Communication  Components of Data Communication  Measuring Capacity of Communication Media  Types of Data Communication  Switching Techniques  Tr...

DATA COMMUNICATION BY: DR. P. KUDJO INTRODUCTION TO DATA COMMUNICATION  Course Contents/Learning Objectives  Concept of Communication  Components of Data Communication  Measuring Capacity of Communication Media  Types of Data Communication  Switching Techniques  Transmission Media  Mobile Telecommunication Technologies  Protocol  Concept of Communication The term “Data Communication” comprises two words: Data and Communication. Data can be any text, image, audio, video, and multimedia files. Communication is an act of sending or receiving data. Thus, Data Communication refers to the exchange of data between two or more networked or connected devices. These devices must be capable of sending and receiving data over a communication medium. Examples of such devices include personal computers, mobile phones, laptops, etc. Concept of Communication A simple network of computing devices  Components of Data Communication Whenever we talk about communication between two computing devices using a network, five most important aspects come to our mind. These are sender, receiver, communication medium, the message to be communicated, and certain rules called protocols to be followed during communication. The communication media is also called transmission media.  Sender: A sender is a computer or any such device which is capable of sending data over a network. It can be a computer, mobile phone, smartwatch, walkie-talkie, video recording device, etc.  Components of Data Communication  Receiver: A receiver is a computer or any such device which is capable of receiving data from the network. It can be any computer, printer, laptop, mobile phone, television, etc. In computer communication, the sender and receiver are known as nodes in a network.  Message: It is the data or information that needs to be exchanged between the sender and the receiver. Messages can be in the form of text, number, image, audio, video, multimedia, etc.  Components of Data Communication  Communication media: It is the path through which the message travels between source and destination. It is also called medium or link which is either wired or wireless. For example, a television cable, telephone cable, ethernet cable, satellite link, microwaves, etc.  Protocols: It is a set of rules that need to be followed by the communicating parties in order to have successful and reliable data communication. You have already come across protocols such as Ethernet and HTTP. Components of Data Communication Components of Data Communication  Measuring Capacity of Communication Media In data communication, the transmission medium is also known as channel. The capacity of a channel is the maximum amount of signals or traffic that it can carry. It is measured in terms of bandwidth and data transfer rate.  Bandwidth Bandwidth of a channel is the range of frequencies available for transmission of data through that channel. The higher the bandwidth, the higher the data transfer rate. Normally, bandwidth is the difference of maximum and minimum frequency contained in the composite  Measuring Capacity of Communication Media  Data Transfer Rate Data travels in the form of signals over a channel. One signal carries one or more bits over the channel. Data transfer rate is the number of bits transmitted between source and destination in one second. It is also known as bit rate. It is measured in terms of bits per second (bps). The higher units for data transfer rates are: 1 Kbps=210 bps=1024 bps 1 Mbps=220 bps=1024 Kbps 1 Gbps=230 bps=1024 Mbps 1 Tbps=240 bps=1024 Gbps  Types of Data Communication Data communication happens in the form of signals between two or more computing devices or nodes. The transfer of data happens over a point-to-point or multipoint communication channel. Data communication between different devices are broadly categorized into 3 types: Simplex communication, Half-duplex communication and Full-duplex communication.  Simplex Communication It is a one way or unidirectional communication between two devices in which one device is sender and other one is receiver. Devices use  Types of Data Communication of the link to transmit the data. For example, data entered through a keyboard or audio sent to a speaker are one way communications.  Half-duplex Communication It is two way or bidirectional communication between two devices in which both the devices can send and receive data or control signals in both directions, but not at the same time. While one device is sending data, the other one will receive and vice-versa.  Types of Data Communication  Full-duplex Communication It is two way or bidirectional communication in which both devices can send and receive data simultaneously. This type of communication channel is employed to allow simultaneous communication, for example, in our mobile phones and landline telephones. The capacity of the transmission link is shared between the signals going in both directions. This can be done either by using two physically separate simplex lines – one for sending and other for receiving, or the capacity of the single channel is shared between the signals travelling in different directions.  Types of Data Communication A simplex, Half-duplex and Full-duplex Communication  Switching Techniques In a network having multiple devices, we are interested to know how to connect the sender and receiver so that one-to-one communication is possible. One solution is to make a dedicated connection between each pair of devices (mesh topology) or between a central device and every other device (a star topology). An alternative to this is switching whereby data is routed through various nodes in a network. This switching process forms a temporary route for the data to be transmitted. Two commonly used switching techniques are; Circuit Switching and Packet Switching.  Switching Techniques  Circuit Switching In circuit switching, before a communication starts, a dedicated path is identified between the sender and the receiver. This path is a connected sequence of links between network nodes. All packets follow the same path established during the connection.  Packet Switching Each information or message to be transmitted between sender and receiver is broken down into smaller pieces, called packets. These packets are then transmitted independently through the network. Different packets of the same message may take different routes  Transmission Media A transmission medium can be anything that can carry signals or data between the source (transmitter) and destination (receiver). In data communication, transmission media are the links that carry messages between two or more communicating devices. Transmission can be classified as guided or unguided.  In guided transmission, there is a physical link made of wire/ cable through which data in terms of signals are propagated between the nodes. These are usually metallic cable, fiber-optic cable, etc. They are also known as wired media.  Transmission Media  In unguided transmission, data travels in air in terms of electromagnetic waves using an antenna. They are also known as wireless media. These dish-shaped antennas are used for sending and receiving data at longer distances. They are mounted on taller buildings so that it would be in line of sight. The waves gradually become weaker and weaker after travelling a certain distance through the air, therefore repeaters are installed to regenerate the signals of the same energy.  Wired Transmission Media Any physical link that can carry data in the form of signals belongs to the category of wired transmission media. Three commonly used guided/ wired media for data transmission are; twisted pair, coaxial cable, and fiber optic cable. Twisted-pair and coaxial cable carry the electric signals whereas the fiber optic cable carries the light signals.  Wired Transmission Media  The Twisted Pair Cable consists of two copper wires twisted like a DNA helical structure. Both the copper wires are insulated with plastic covers. Usually, a number of such pairs are combined together and covered with a protective outer wrapping. Each of the twisted pairs act as a single communication link. The use of twisted configuration minimizes the effect of electrical interference from similar pairs close by and they are less expensive. These cables are most commonly used in telephone lines and LANs. They are of two types; Unshielded twisted-pair (UTP) and Shielded twisted-pair (STP).  Wired Transmission Media  The Coaxial cable is another type of data transmission medium that is better shielded and has more bandwidth than a twisted pair. It has a copper wire at the core of the cable which is surrounded with insulating material. The insulator is further surrounded with an outer conductor (usually a copper mesh) which is wrapped in a plastic cover. Its shielded design allows the cable's copper core to transmit data quickly without interference of environmental factors. These types of cables are used to carry signals of higher frequencies to a longer distance.  Wired Transmission Media  The Fiber Optic cable carries data as light, which travels inside a thin fiber of glass and uses refraction to direct the light through the media. A thin transparent strand of glass at the center is covered with a layer of less dense glass called cladding. It is then covered with an outer jacket made of PVC or Teflon. Such types of cables are usually used in backbone networks because they are of light weight and have higher bandwidth which means higher data transfer rate. The signals can travel longer distances and electromagnetic noise cannot affect the cable. However, optic fibers are expensive and unidirectional.  Wireless Transmission Media In wireless communication technology, information travels in the form of electromagnetic signals through air. Electromagnetic spectrum of frequency ranging from 3 KHz to 900 THz is available for wireless communication. The electromagnetic spectrum range can be divided into 4 categories; Radio waves, Microwaves, Infrared waves and Visible or Light waves according to their frequency range. Wireless technologies allow communication between two or more devices in short to long distance without requiring any physical media. There are many types of wireless communication technologies such as Bluetooth, WIFI, WiMAX etc.  Wireless Transmission Media  Bluetooth is a short-range wireless technology that can be used to connect mobile phones, mouse, headphones, keyboards, computers, etc. wirelessly over a short distance. All these bluetooth-enabled devices have a low cost transceiver chip that uses the unlicensed frequency band of 2.4 GHz to transmit and receive data. These bluetooth devices can send data within a range of 10 meters in a PAN called piconet with a speed of 1-to-2 Mbps and allows for up to 255 devices to build a network where 8 devices can communicate at the same time and remaining devices can be inactive, waiting for a response command from the master device.  Wireless Transmission Media  Wireless Local Area Network (LAN) is another way of wireless communication and it is a popular way to connect to the Internet. The international organization IEEE assigns numbers to each different standards of LAN. The wireless LAN is numbered 802.11 and it is popularly known as Wi-Fi. These networks consist of communicating devices such as laptops and mobile phones as well as the network device called Access Points (APs) which is installed in buildings or floors. An Access Point is a device that is used to create a wireless LAN by connecting to a wired router, switch, or hub. Wi-Fi gives users the flexibility to move around within the network area while being connected Wired/ Wireless Transmission Media Wired and Wireless Transmission Media  Mobile Telecommunication Technologies Today the mobile phone network is the most used network in the world. The ability to be connected to the network on-the-go makes it very convenient to communicate with people via call or instant messages and also access the internet through wireless connections. The architecture of the mobile network has rapidly evolved over the last few decades. The different landmark achievements in mobile communication technologies are classified as different generations. They are identified as 1st Gen, 2nd Gen, 3rd Gen, 4th Gen, and 5th Gen.  Mobile Telecommunication Technologies  The First Generation (1G) mobile network system came around 1982. It was used to transmit only voice calls. The analog signals were used to carry voices between the caller and receiver.  The Second Generation (2G) mobile network system came around 1991. Instead of analog signals, voice calls were transmitted in digital form thus providing improved call quality. It also enabled an additional service to send SMS and MMS.  The Third Generation (3G) mobile network technology was developed during late 90s, but it was introduced commercially around 2001. It offered both digital voice and data services.  Mobile Telecommunication Technologies  The Fourth Generation (4G) network system supports interactive multimedia, voice, video, wireless internet and other broadband services. Demand for faster data is always increasing that is why the 4G mobile networks were developed. 4G is much faster than 3G and this has revolutionized the field of telecommunication by bringing the wireless experience to a new level altogether.  The Fifth Generation (5G) is currently under development. It is expected to be a milestone development for the success of IoT and Machine-to-Machine (M2M) communications (wired and wireless).  Protocol In communication, Protocol is a set of standard rules that the communicating parties — the sender, the receiver, and all other intermediate devices need to follow. The sender and receiver can be parts of different networks, placed at different geographic locations. The data transfer rates in different networks can vary, requiring data to be sent in different formats.  The Need for Protocols We need protocols for different reasons such as flow control, access control, addressing, etc. Flow control is required when the sender and receiver have different speeds of sending and receiving the data. Access control is required to decide which nodes in a communication channel will access the link shared among them at a particular instant of time. If all the rules or protocols of a communication network are defined at one place, it becomes complex to ensure that communicating parties  The Need for Protocols Protocols also define; How computers identify one another on a network. The form to which the data should be converted for transit. How to rearrange the packets and process them at the destination. Ensuring that all the data have reached the destination without any loss. How to decide whether the data received is for that node or to be forwarded to another node.  HyperText Transfer Protocol (HTTP) HTTP which stands for HyperText Transfer Protocol is the primary protocol used to access the World Wide Web. HTTP is a request-response (client-server) protocol that runs over TCP. The common use of HTTP is between a web browser (client) and a web server (server). HTTP facilitates access of hypertext from the World Wide Web by defining how information are formatted and transmitted. Once a user opens a web browser and types in the URL of the intended web page, a logical communication link between the user and the web server is created. A web page is written using a markup  File Transfer Protocol (FTP) File Transfer Protocol (FTP) is the protocol used for transferring files from one machine to another. Like HTTP, FTP also works on a client-server model. When a user requests for a file transfer with another system, FTP sets up a connection between the two nodes for accessing the file. Optionally, the user can authenticate using user ID and password then specifies the file name and location of the desired file. After that, another connection sets up and the file transfer happens directly between the two machines. File transfer between the two devices seems simple and straightforward because FTP takes care  Point to Point Protocol (PPP) Point to Point Protocol (PPP) is a communication protocol which establishes a dedicated and direct connection between two communicating devices. This protocol defines how two devices will authenticate each other and establish a direct link between them to exchange data. For example, two routers with direct connection communicate using PPP, The Internet user who connects his/her home computers to the server of an Internet Service Provider (ISP) through a modem also use PPP. The communicating devices should have duplex modes for using this protocol. This protocol maintains data integrity ensuring that the packets arrive in order. It intimates the  Simple Mail Transfer Protocol (SMTP) Simple Mail Transfer Protocol (SMTP) is a protocol used for email services. It uses information written on the message header (like an envelope on a letter sent by post) and is not concerned with the content of the email message. Each email header contains email addresses of recipients. The email containing header and body are entered into a queue of outgoing mails. The SMTP sender program takes mails from the outgoing queue and transmits them successfully to the destination(s). It removes the corresponding receiver’s email address from the mail’s destination list of the outgoing queue. The SMTP receiver program accepts each mail that has arrived and places  Transmission Control Protocol (TCP)/ Internet Protocol (IP) Transmission Control Protocol/ Internet Protocol (TCP/TP) is a set of standardized rules that uses a client-server model of communication in which a user (client) requests a service by a server in the network. The TCP/ IP ensures that each computer or node connected to the Internet is assigned an IP address, which is used to identify each node independently. It can be considered to be the adhesive that holds the whole internet together. TCP ensures that the message is broken into smaller units (IP packets) and are routed (transmitted) through the internet along a path from one router to the next while guaranteeing a successful delivery of packets to the THANK YOU