CN11Introduction.pptxCN11Introduction.pptx

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1. COMPUTER NETWORK UNIT 1 CHAPTER 1 INTRODUCTION Shraddha Kokate

2. DATA COMMUNICATION 1 ] Telecommunication- which includes telephony, telegraphy, and television, means communication at a distance (tele is Greek for "far"). 2 ] Data - refers to information presented in whatever form is agreed upon by the parties creating and using the data 3] Data communication- Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable.

3. CHARACTERISTICS Delivery- The system must deliver data to the correct destination Accuracy. The system must deliver the data accurately. Timeliness- The system must deliver data in a timely manner Jitter- Jitter refers to the variation in the packet arrival time

4. COMPONENTS 1] Message:- The message is the information (data) to be communicated. It include text, numbers, pictures, audio, and video. 2] Sender :- The sender is the device that sends the data message. It can be a computer, workstation, telephone handset, video camera. 3] Receiver :- The receiver is the device that receives the message 4] Transmission medium. The transmission medium is the physical path by which a message travels from sender to receiver. It include twisted-pair wire, coaxial cable, fiber -optic cable etc. 5] Protocol- A protocol is a set of rules that govern data communications.

5. Data Representation Text Number Image Audio Video

6. Data Flow Simplex In simplex mode, the communication is unidirectional, as on a one-way street. Only one of the two devices on a link can transmit; the other can only receive Half-Duplex In half-duplex mode, each station can both transmit and receive, but not at the same time. : When one device is sending, the other can only receive, and vice versa Full-Duplex In full-duplex mode (also called duplex), both stations can transmit and receive simultaneously

7. NETWORKS 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. Network Criteria 1] Performance Performance can be measured including transit time and response time. Transit time is the amount of time required for a message to travel from one device to another. Response time is the elapsed time between an inquiry and a response. Performance is often evaluated by two networking metrics: throughput and delay.

8. Network Criteria 2 ] Reliability Network reliability is measured by the frequency of failure, the time it takes a link to recover from a failure, and the network's robustness . 3] Security Network security issues include protecting data from unauthorized access, protecting data from damage and development, and implementing policies and procedures for recovery from breaches and data losses. Types of Connections 1] Point-to-Point :- A point-to-point connection provides a dedicated link between two devices. 2] Multipoint :-A multipoint (also called multidrop) connection is one in which more than two specific devices share a single link

9. TOPOLOGY Refers to the way in which a network is made Bus Topology In case of Bus topology, all devices share single communication line or cable. Bus topology may have problem while multiple hosts sending data at the same time

10. Star Topology All hosts in Star topology are connected to a central device, known as hub device, using a point-to-point connection. There exists a point to point connection between hosts and hub.  If hub fails, connectivity of all hosts to all other hosts fails

11. Ring Topology In ring topology, each host machine connects to exactly two other machines, creating a circular network structure. When one host tries to communicate or send message to a host which is not adjacent to it, the data travels through all intermediate hosts. Failure of any host results in failure of the whole ring. Thus, every connection in the ring is a point of failure. 

12. Mesh Topology In this type of topology, a host is connected to one or multiple hosts . This topology has hosts in point-to-point connection with every other host or may also have hosts which are in point-to-point connection to few hosts only.

13. NETWORK MODEL Local Area Network A computer network spanned inside a building and operated under single administrative system is generally termed as Local Area Network (LAN). LAN covers an organization’ offices, schools, colleges or universities. Number of systems connected in LAN may vary from as least as two to as much as 16 million. LAN provides a useful way of sharing the resources between end users. The resources such as printers, file servers, scanners, and internet are easily sharable among computers.

14. ADVANTAGES AND DISADVANTAGES ADVANTAGES DISADVANTAGES Sharing of resources Data security problem Client and server relationship Limitation of distance Software program sharing Server crashes may affect all computers Securing of data Setting up a LAN is expensive Communication is easy, fast, and time-saving Computer identification

15. NETWORK MODEL Metropolitan Area Network The Metropolitan Area Network (MAN) generally expands throughout a city such as cable TV network. It can be in the form of Ethernet , Token-ring, ATM, or Fibre Distributed Data Interface (FDDI). Metro Ethernet is a service which is provided by ISPs. This service enables its users to expand their Local Area Networks. For example, MAN can help an organization to connect all of its offices in a city. Backbone of MAN is high-capacity and high-speed fibre optics. MAN works in between Local Area Network and Wide Area Network

16. Advantages of MAN : ➨It utilizes drawbacks of both LAN and WAN to provide larger and controllable computer network. ➨MAN requires fewer resources compare to WAN. This saves the implementation cost. ➨It helps people interface fast LANs together. This is due to easy implementation of links. ➨It provides higher security compare to WAN. ➨It helps in cost effective sharing of common resources such as printers etc. ➨Like LAN and WAN, it also offers centralized management of data and files. Disadvantages of MAN : ➨It is difficult to manage the network once it becomes large. ➨It is difficult to make the system secure from hackers and industrial espionage. ➨Network installation requires skilled technicians and network administrators. This increases overall installation and management costs. ➨It requires more cables for connection from one place to the other compare to LAN .

17. NETWORK MODEL Wide Area Network The Wide Area Network (WAN) covers a wide area which may span across provinces and even a whole country. Generally, telecommunication networks are Wide Area Network. These networks provide connectivity to MANs and LANs. Since they are equipped with very high speed backbone, WANs use very expensive network equipment.

18. Advantages and Disadvantages Advantages Disadvantages Centralizes IT infrastructure High setup costs Boosts your privacy Security Concerns Increases bandwidth Maintenance Issues Eliminates Need for ISDN Guaranteed uptime Cuts costs, increase profits

19. INTERNET The Internet is a structured, organized system A network is a group of connected communicating devices such as computers and printers. An internet (note the lowercase letter i ) is two or more networks that can communicate with each other. The most notable internet is called the Internet (uppercase letter I), a collaboration of more than hundreds of thousands of interconnected networks. The Internet today is not a simple hierarchical structure. It is made up of many wide- and local-area networks joined by connecting devices and switching stations. services of Internet service providers ( lSPs ). 1] International Internet Service Providers At the top of the hierarchy are the international service providers that connect nations together.

20. INTERNET 2 ] National Internet Service Providers The national Internet service providers are backbone networks created and maintained by specialized companies. 3] Regional Internet Service Providers Regional internet service providers or regional ISPs are smaller ISPs that are connected to one or more national ISPs 4] Local Internet Service Providers Local Internet service providers provide direct service to the end users

21. Protocols The key elements of a protocol are syntax, semantics, and timing. 1] Syntax:- The term syntax refers to the structure or format of the data, meaning the order in which they are presented. 2] Semantics:- The word semantics refers to the meaning of each section of bits 3] Timing:- Term timing refers to two characteristics: when data should be sent and how fast they can be sent

22. Standards Data communication standards fall into two categories 1] de facto (meaning "by fact" or "by convention") :- Standards that have not been approved by an organized body but have been adopted as standards through widespread use are de facto standards. 2] de jure (meaning "by law" or "by regulation“) Those standards that have been legislated by an officially recognized body are de jure standards.

23. Standards Organizations:- Standards are developed through the cooperation of standards creation committees, forums, and government regulatory agencies Standards Creation Committees International Organization for Standardization (ISO) International Telecommunication Union-Telecommunication Standards Sector (ITU-T) American National Standards Institute (ANSI) Institute of Electrical and Electronics Engineers (IEEE) Electronic Industries Association (EIA)

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