1st Lecture Chapter 1 Introduction to Data Communications PDF

Data Communications I. Introduction to Data Communications 1ST Semester, A.Y 2024-2025  Data Communications I. Introduction to Data Communications...

Data Communications I. Introduction to Data Communications 1ST Semester, A.Y 2024-2025  Data Communications I. Introduction to Data Communications 1ST Semester, A.Y 2024-2025 Notes from previous slide: 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. ------Picture: Figure: A simple network of computing devices. four different types of devices — computer, printer, server and switch are connected to form the network. These devices are connected through a media to the network, which carry information from one end to other end. Effective and efficient data communication and networking facilities are vital to any enterprise. Three different forces have consistently driven the architecture and evolution of data communications and networking facilities: traffic growth, development of new services, and advances in technology. Outline Topic Introduction to Data Communications Data Communications Network Architecture, Protocols, and Standards I. Networks II. Circuit Switching III. Packet Switching IV. Protocols V. Internet Standards Organizations for Data Communications Intended Learning Outcome Define the following terms: data, data communications, data communications circuit, and data communications network Give a brief description of the evolution of data communications Define data communications network architecture Describe data communications protocols Describe the basic concepts of connection-oriented and connectionless protocols Describe syntax and semantics and how they relate to data communications Define data communications standards and explain why they are necessary  DATA Refers to information presented in whatever form in agreed upon by the parties creating and using the data. INTRODUCTION DATA COMMUNICATIONS Are the exchange of data between two devices via some form of transmission medium such as wire cable. Notes from previous slide: Data can be any text, image, audio, video, and multimedia files. Data communications deals with the transmission of signals in a reliable and efficient manner. Networking deals with the technology and architecture of the communications networks used to interconnect communicating devices. Data Communications”, deals with the most fundamental aspects of the communications function, focusing on the transmission of signals in a reliable and efficient manner. Consider this example: a sequence of numbers “100, 150, 200” is just data. However, if you put it into context: “The sales of a product over the past three months were 100, 150, and 200 units, The fundamental purpose of a communications system is the exchange of data between two parties. This section introduces a simple model of communication. Source - generates data to be transmitted Transmitter - converts data into transmittable signals Transmission System - carries data from source to destination Receiver - converts received signal into data Destination - takes incoming data  Enables an information system to deliver information DATA Improves the flexibility of data collection and transmission COMMUNICATIONS DO Basis of virtual organizations Provides e-collaboration  BASIC CONCEPT OF DATA COMMUNCATION ❑ Bandwidth: Amount of data that can be transferred from one point to another in a certain time period. ❑ Attenuation: Loss of power in a signal as it travels from the sending device to the receiving device. ❑ Broadband: Multiple pieces of data, sent simultaneously to increase transmission rate. ❑ Narrowband: Voice-grade transmission channel capable of transmitting a maximum of 56,000 bps, so only a limited amount of information can be transferred. ❑ Protocols: Rules that govern data communication - Error detection, message length, and transmission speed. 5 Components of Data TRANSMITTER RECEIVER MEDIUM MESSAGE PROTOCOL Communication Notes from previous slide: Transmitter: The transmitter is the device that sends the message. It can be a computer, workstation, telephone handset, video camera, and so on. Receiver: The receiver is the device that receives the message. It can be a computer, workstation, telephone handset, television, and so on. Medium: The transmission medium is the physical path by which a message travels from sender to receiver. It can consist of twisted pair wire, coaxial cable, fiber-optic cable, laser or radio waves (terrestrial or satellite microwave). Message: The message is the transmission (data) to be communicated. It can consist of text, number, pictures, sound, or video or any combination of these. Protocol: A protocol is a set of rules that governs data communication. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating, just as a person speaking German cannot be understood by a person who speaks only Japanese. 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. We know that the sender and receiver can be parts of different networks, placed at different geographic locations. Besides, the data transfer rates in different networks can vary, requiring data to be sent in different formats. 11.8.1 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 Protocol – Agreement between the communicating devices. HTTP stands for HyperText Transfer Protocol. It is the primary protocol used to access the World Wide Web,  DATA Representation ❑ Text: ASCII: 7-bit pattern (128 different symbols) Extended ASCII: 8-bit pattern (with an extra 0 at left from 00000000 to 0111111 Unicode: 32 bits pattern (65,536,216) symbols, which is definitely enough to represent any symbol in the world. ❑ Numbers: represented by bit pattern (binary number) ❑ Images : represented by matrix of pixels (picture element), small dot. The size of pixel represent the resolution. ❑ Audio: represent sound by continuous (analog) signal ❑ Video: can be analog or digital signal DATA FLOW Notes from previous slide: Date Flow/ Type of Data Communication: As we know that data communication is communication in which we can send or receive data from one device to another. The data communication is divided into three types: 1. Simplex Communication: It is one-way communication or we can say that unidirectional communication in which one device only receives and another device only sends data and devices uses their entire capacity in transmission. For example, IoT, entering data using a keyboard, listing music using a speaker, etc. 2. Half Duplex communication: It is a two-way communication, or we can say that it is a bidirectional communication in which both the devices can send and receive data but not at the same time. When one device is sending data then another device is only receiving and vice-versa. For example, walkie-talkie. 3. Full-duplex communication: It is a two-way communication or we can say that it is a bidirectional communication in which both the devices can send and receive data at the same time. For example, mobile phones, landlines, etc. The main types are simplex (one-way communication), half-duplex (two-way communication, but not simultaneously), and full-duplex (two-way communication simultaneously).  NETWORKS NETWORK NODE LINK growth of number & power of computers is driving need for interconnection also seeing rapid integration of voice, data, image & video technologies two broad categories of communications networks: Local Area Network (LAN) Wide Area Network (WAN) Notes from previous slide: A set of processing nodes connected by communication links. A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. A link can be a cable, air, optical fiber, or any medium which can transport a signal carrying information. The number of computers in use worldwide is in the hundreds of millions, with pressure from users of these systems for ways to communicate among all these machines being irresistible. Advances in technology have led to greatly increased capacity and the concept of integration, allowing equipment and networks to deal simultaneously with voice, data, image, and even video. Have two broad categories of networks: Local Area Networks (LAN) and Wide Area Networks (WAN).  COMMUNICATION MEDIA Selection is a basic choice internal use entirely up to business long-distance links made by carrier Rapid technology advances change mix fiber optic wireless Transmission costs still high Hence interest in efficiency improvements Notes from previous slide: A simple recall: The basic building block of any communications facility is the transmission line. One of the basic choices facing a business user is the transmission medium. For use within the business premises, this choice is generally completely up to the business. For long-distance communications, the choice is generally but not always made by the long-distance carrier. In either case, changes in technology are rapidly changing the mix of media used. The ever-increasing capacity of fiber optic channels is making channel capacity a virtually free resource. However, switching is now becoming the bottleneck. The growing use of wireless transmission, is a result of the trend toward universal personal telecommunications and universal access to communications. Despite the growth in the capacity and the drop in cost of transmission facilities, transmission services remain the most costly component of a communications budget for most businesses. Thus, the manager needs to be aware of techniques that increase the efficiency of the use of these facilities, such as multiplexing and compression. Many types of communication media: twisted (copper) pair coaxial (copper) cable radio infrared fiber optic cable satellites  PHYSICAL STRUCTURE ❑ Type of Connection Point to Point - single transmitter and receiver Multipoint - multiple recipients of single transmission ❑ Physical Topology Connection of devices Type of transmission - unicast, mulitcast, broadcast  TYPE OF CONNECTION ❑ Point to Point - single transmitter and receiver Point-to-Point protocol (PPP) defines how two devices will authenticate each other and establish a direct link between them to exchange data. Point to Point Protocol (PPP) 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 users who connect their 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 Notes 2024-25 Data Communication 219 data integrity ensuring that the packets arrive in order. It intimates the sender  TYPE OF CONNECTION ❑ Multipoint (multidrop) connection: TYPE OF TOPOLOGIES BUS TOPOLOGY Notes from previous slide: Bus topology In a Bus topology, one long cable acts as a single communication channel, and all the nodes or computers are connected to this cable. The cable that uses in bus topology is RJ-45 cable or coaxial cable. Advantages of Bus topology Easy to add or remove computer systems in a network. Required only cable to form the whole network. It is less expensive. It broadcast the message to all the devices that are connected through the Cable. It is easy to maintain. In case of any computer failure, there will be no effect on any other nodes. Disadvantages of Bus topology The entire network will be failed in case of cable failure. We can’t send private messages in bus topology. It takes more time to pass messages from one node to another node. The length of the cable is limited data transmission is done in only one direction. RING TOPOLOGY Notes from previous slide: Ring topology It is called Ring topology because it forms a ring, and in a ring topology each node is strongly connected with its adjacent node. Advantages of Ring topology It forms a strong network. Each and every node can share data with other nodes connected through a ring topology Transmission rate of data is very high. The data sent through this topology will be broadcast. Disadvantages of Ring topology It is a very difficult task to add new nodes. If we want to send data from a source to a destination machine then data will be unnecessarily passed to all the nodes. A single point of failure, that means if a single node goes down then the entire network goes down. It is very difficult to recover this topology if any particular machine is not working properly. We can’t send private messages. STAR TOPOLOGY Notes from previous slide: Star topology In Star topology all the computer systems are connected with a central device called HUB and the sharing of data is only possible through HUB. Advantages of Star topology It broadcast the messages. It is less expensive due to less cable. easy to connect a new computer system without affecting the rest of the network. If one system is failed, then it would not be a failure of the entire network. Disadvantages of Star topology In Star topology, we must require a network device like HUB, Switch, etc. If two systems want to share the data, then sharing is only possible through HUB. We should not send private messages (HUB will broadcast the message). If HUB is failed then the entire network will be failed. MESH TOPOLOGY Notes from previous slide: Mesh Topology In this topology every node is directly connected with each other, so we can directly send the data to the destination machine without going to the intermediate machine. Advantages of Mesh topology mesh topology is a very good topology to send private messages. All nodes are directly associated with another node. So, it provides point to point connection. Unlike ring topology, if a particular machine is failed then the entire network will not fail. multiple devices can send or receive data simultaneously. Disadvantages of Mesh topology It is very difficult to add some new nodes because each and every computer is directly connected to another. If a particular machine not working then we can’t send or receive data from the failed machine. HYBRID TOPOLOGY Notes from previous slide: Hybrid topology A combination of various different topologies such as Bus, Star, Ring, etc is called Hybrid topology. Advantages of Hybrid topology It is very flexible. We can easily add or remove new nodes without affecting the rest of the network. Hybrid topology is used to create large networks. We can modify it as per requirement. Disadvantages of Hybrid topology It is very expensive. Design of a Hybrid topology is very complex. Installation process is very difficult. TREE TOPOLOGY Notes from previous slide: Tree topology In this topology, all the nodes are connected like branches of a tree. the combination of Bus and Star topology is called Tree topology. Advantages of Tree topology We can easily add or remove new nodes without affecting the rest of the network. Tree topology is used to create large networks. It is easy to maintain. We can easily identify faults in tree topology. It is a combination of Bus and Star topology. Disadvantages of Tree topology Design of a Tree topology is very complex as compared to any other topology. If the first level of a node is not working properly then the next level of nodes also faces the same problem. It is very expensive as compared to any other topology.  CATEGORIES OF NETWORKS ❑ Local Area Networks (LANs) Short distances Designed to provide local interconnectivity ❑ Metropolitan Area Networks (MANs) Provide connectivity over areas such as a city, a campus ❑ Wide Area Networks (WANs) Long distances Provide connectivity over large areas  SWITCHING TECHNIQUES 1 Circuit Switching 2 Packet Switching  CIRCUIT SWITCHING Uses a dedicated communications path established for duration of conversation Comprising a sequence of physical links With a dedicated logical channel Notes from previous slide: 11.5.1 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. In earlier days, when we placed a telephone call, the switching equipment within the telephone system finds out a physical path or channel all the way from our telephone at home to the receiver’s telephone. This is an example of circuit switching. All resources (e.g. communication links) needed by a “call” are dedicated to that call for its duration. In a circuit-switching network, a dedicated communications path is established between two stations through the nodes of the network. That path is a connected sequence of physical links between nodes, with a logical channel dedicated to the connection. Data generated by the source station are transmitted along the dedicated path as rapidly as possible. The most common example of circuit switching is the telephone network. eg. telephone network/ A voice telephone call See illustration above. Call from A to F blocks calling from B to E. Resource reservation: resources are always available when needed by a call, providing a guaranteed quality of service.  PACKET SWITCHING Data sent out of sequence Small chunks (packets) of data at a time Packets passed from node to node between source and destination Used for terminal to computer and computer to computer communications Notes from previous slide: Data entering network is divided into small chunks called “packets”. A packet-switching network uses a quite different approach, without need to dedicate transmission capacity along a path through the network. Rather, data is sent in a sequence of small chunks, called packets. Each packet is passed through the network from node to node along some path leading from source to destination. At each node, the entire packet is received, stored briefly, and then transmitted to the next node. Packet-switching networks are commonly used for terminal-to-computer and computer-to-computer communications. See illustration above: Packets traversing the network share network resources with other packets. Demand for resources may exceed resources available: Contention: two packets arrive simultaneously at D destined for E or F Queuing (waiting) for resources. Statistical sharing of resources.  WHY RESOURCE SHARING? To save/make money! Circuit switching: give each caller 100 Kbits/sec capacity. 10 callers can be supported. Packet switching: with 35 calls in progress, the probability that 10 or more callers are simultaneously active is less than 0.0004. Many more callers can be supported with only a small probability of contention. If users are “bursty”, then packet switching is advantageous.  PROTOCOLS Rules by which active network elements communicate with each other is a protocol Protocols define the formats and timing of messages exchanged, and actions taken on receipt of messages for peer entities  STANDARD BODIES Industry Canada National Research Council (Canada) (NRC-CNRC) National Canadian Standards Association (CSA) Standard Bodies American National Standards Institute (ANSI) US National Institute of Standards and Technology (NIST)  STANDARD BODIES International Organization for Standardization (ISO) International International Telecommunications Union (ITU) Standard Bodies Non- governmental Organizations  STANDARD BODIES ISO (www.iso.ch) Non-treaty agency of the United Nations. Collaborates standards development for information technology. ITU (www.itu.int) ITU-T: telecom sector of ITU UN treaty agency that sets telecommunications standards. ANSI (www.ansi.org) The US national standards body. Coordinates and accredits standards development across the US. IEEE (www.ieee.org) US based international professional organization. Develops standards and submits to ANSI for approval.  STANDARD BODIES Telcordia (www.telcordia.com) Coordinates and develops standards for US telephone service ETSI (www.etsi.org) European Telecommunications Standards Institute Similar to Telcordia, but for Europe IAB / IETF / IRTF Internet Architecture Board (www.iab.org) Internet Engineering Task Force (www.ietf.org) Internet Research Task Force (www.irtf.org) Object Management Group (OMG) (www.omg.org) Consists of many companies Develops/co-ordinates CORBA/IDL, UML standards WWW consortium (www.w3.org) Develops/co-ordinates standards such as HTTP, HTML, XML, …  THE INTERNET Internet evolved from ARPANET first operational packet network applied to tactical radio & satellite nets also had a need for interoperability led to standardized TCP/IP protocols Four “classic” (1980s) Internet applications: Electronic mail Usenet news Remote login File transfer  Networking Today Networks in Our Past and Daily Lives Interconnecting Our Lives Networking Impacts in Our Daily Lives ❑ Networks support the way we learn. ❑ Networks support the way we communicate. ❑ Networks support the way we work. ❑ Networks support the way we play.  The concept of any device, to any content, in anyway is a The Changing major global trend that requires significant changes to the way devices are used. This trend is known as Bring Your Own Environment Device (BYOD).  Network Trends Online Collaboration | Cloud Computing Cloud computing offers the following potential benefits: Organizational flexibility Agility and rapid deployment Reduced cost of infrastructure Refocus of IT resources Creation of new business models THANK YOU!