Data Communications AND NetworkingData Communications AND Networking,

1.2 1-1 DATA COMMUNICATIONS 1-1 DATA COMMUNICATIONS The term The term telecommunication telecommunication means communication at a means communication at a distance. The word distance. The word data data refers to information presented refers to information presented in whatever form is agreed upon by the parties creating in whatever form is agreed upon by the parties creating and using the data. and using the data. Data communications Data communications are the are the exchange of data between two devices via some form of exchange of data between two devices via some form of transmission medium such as a wire cable. transmission medium such as a wire cable. Fundamental Characteristics: Fundamental Characteristics: Delivery, Accuracy, Timeliness, Jitter Delivery, Accuracy, Timeliness, Jitter Components (Message, Sender, Receiver, Transmission Medium, Protocol). Data Représentation (Text, Number, Images, Audio, Video) Data Flow (Simplex, Duplex, Half Duplex) Topics discussed in this section: Topics discussed in this section:

Components 1. Message. The message is the information (data) to be communicated. Popular forms of information 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, and so on. 3. Receiver. The receiver is the device that receives the message. It can be a computer, workstation, telephone handset, television, and so on. 4. Transmission medium. The transmission medium is the physical path by which a message travels from sender to receiver. Some examples of transmission media include twisted-pair wire, coaxial cable, fiber-optic cable, and radio waves. 5. Protocol. A protocol is a set of rules that govern data communications. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating, just as a person speaking French cannot be understood by a person who speaks only Japanese. 1.3

1.4 Figure 1.1 Five components of data communication

Data Representation  Text (Unicode, American Standard Code for Information Interchange (ASCII))  Numbers  Images ( Divided into pixel with size in bit patterns, has color scheme of RGB- red, green, and blue or YCM- yellow, cyan, and magenta.  Audio  Video 1.5

Data Flow  Simplex  Duplex  Half Duplex  Full Duplex 1.6

1.7 Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)

1.8 1-2 NETWORKS 1-2 NETWORKS A A network network is a set of devices (often referred to as is a set of devices (often referred to as nodes nodes) ) connected by communication connected by communication links links. A node can be a . A node can be a computer, printer, or any other device capable of sending computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the and/or receiving data generated by other nodes on the network. network. Distributed Processing Network Criteria (performance, reliability, security) Physical Structures (Type of Connection: Multipoint, Point to Point. Topology: Mesh, Star, Bus, Ring, Hybrid) Network Models (OSI, TCP/IP) Categories of Networks (PAN, LAN, MAN, WAN) Interconnection of Networks: Internetwork Topics discussed in this section: Topics discussed in this section:

1.9 Figure 1.3 Types of connections: point-to-point and multipoint

1.10 Figure 1.4 Categories of topology

1.12 Figure 1.5 A fully connected mesh topology (five devices)

1.13 Figure 1.6 A star topology connecting four stations

1.14 Figure 1.7 A bus topology connecting three stations Back Bone Cable are connected to Drop line through Taps. Signal becomes weak as it travels further distance. Advantages: Ease of Installation. Uses less cables. Less complex. Disadvantages: Difficult to fault isolation and reconnection. Difficult to add new devices. Signal reflection at tapes reduces the signal quality. A fault or break in the bus cable stops all transmission.

1.15 Figure 1.8 A ring topology connecting six stations Easy to install and reconfigure. Fault isolation is simplified. If one device does not receive a signal within a specified period, it can issue an alarm. The alarm alerts the network operator to the problem and its location. The only constraints are media and traffic considerations (maximum ring length and number of devices). Unidirectional traffic can be a disadvantage. In a simple ring, a break in the ring (such as a disabled station) can disable the entire network. Solution: Dual Ring.

1.16 Figure 1.9 A hybrid topology: a star backbone with three bus networks

1.17 Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet

1.18 Figure 1.11 WANs: a switched WAN and a point-to-point WAN

1.19 Figure 1.12 A heterogeneous network made of four WANs and two LANs

1.20 1-3 THE INTERNET 1-3 THE INTERNET The The Internet Internet has revolutionized many aspects of our daily has revolutionized many aspects of our daily lives. It has affected the way we do business as well as the lives. It has affected the way we do business as well as the way we spend our leisure time. The Internet is a way we spend our leisure time. The Internet is a communication system that has brought a wealth of communication system that has brought a wealth of information to our fingertips and organized it for our use. information to our fingertips and organized it for our use. A Brief History The Internet Today (ISPs) Topics discussed in this section: Topics discussed in this section:

 Came into existence in 1969 only after Packet Switched Network was invented in 1961 at MIT by Leonard Kleinrock.  DoD (Dept of Defense) through ARPA (Advanced Research Projects Agency) represented ARPANET in ACM (Association of Comuting Machinery) meeting in 1967.  Introduced IMP (Interface Message Processor).  In 1969, UCLA – UCSB – SRI – UoU got connected.  University of California Los Angeles – UCLA  University of California Santa Barbara – UCSB  University of Utah – UoU  Sanford Research Institute (SRI)  Software Support by NCP – Network Control Protocol.  1972, Vint Cerf and Bob Kahn came up with paper on TCP with networking concepts of encapsulation, datagram, gateways, end to end delivery of packets.  Soon TCP was split into TCP and IP.  In 1981, UC Berkeley modified the UNIX operating system to include TCP/IP which popularized Internetworking.  Then came creation of CSNET in 1981. Computer Science Network (CSNET) was a network sponsored by the National Science Foundation (NSF).  In 1983, ARPANET split into two networks: Military Network (MILNET) for military users and ARPANET for nonmilitary users.  Today, it is managed by ISP – Internet Service Providers. 1.21 Brief History Brief History

1.22 Figure 1.13 Hierarchical organization of the Internet ISP – Internet Service Provider NAP – Network Access Point ISP Communicate with each others network through NAP

Standards Organization  ISO – International Organization of Standardization  ITU-T – International Telecommunication Union Telecommunication Standards formed CCITT in 1993 for research.  CCITT – Consultative Committee for International Telegraphy and Telephony.  ANSI – American National Standards Institutions.  IEEE – Institute of Electric and Electronics Engineers  EIA – Electronic Industries Association  FCC – Federal Communication Commission  RFC – Request for Comment  How about Controlling body in India? 1.23

Standards Organization in INDIA  Press Council of India (PCI),  News Broadcasting Standards Authority (NBSA),  Central Board of Film Certification (CBFC),  Telecom Regulatory Authority of India (TRAI),  Indian Broadcasters Federation (IBF),  News Broadcasters Association (NBA),  Indian Media Group (IMG),  Indian Society of Advertisers (ISA),  The Advertising Standards Council of India (ASCI),  Advertising Agencies Association of India (AAAI),  Media Research Users Council (MRUC),  Audit Bureau of Circulations (ABC),  Press Trust of India (PTI),  Confederation of Indian Industry (CII),  the Associated Chambers of Commerce and Industry of India (ASSOCHAM),  Federation of Indian Chambers of Commerce and Industry (FICCI),  United News of India (UNI) 1.24

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