1.1 CSC311-DATA COMMUNICATION AND NETWORKING Introduction

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DATA COMMUNICATIONS The term telecommunication means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable. Components Data Representation Data Flow Topics discussed in this section:

1.4 Figure 1.1 Five components of data communication

Components of data communication  QUIZ: 1.The information to be communicated in a data communication system is the ________. a. medium b. protocol c. message d. transmission 2. The _______ is the physical path over which a message travels. a. protocol b. medium c. signal d. all of the above

Networks  Network is a set of devices(referred to as nodes) connected by media links.  Distributed processing - task is divided among multiple computers Advantages:  Security  Distributed databases  Faster problem solving  Security through redundancy  Collaborative processing

Network Criteria Data communication network criteria PerformanceReliabilitySecurity

1. Performance  Factors  Number of users  Type of transmission media – Ex. Fiber optic cable.  Hardware  Software

2. Reliability  Factors  Frequency of failure  Recovery time of a network after a failure  Catastrophe – Ex. Fire, earthquake, or theft

3. Security  Factors  Unauthorized access.  Viruses.

Applications of Data communication networks Marketing and sales Financial services Electronic messaging Manufacturing Electronic messaging Cable television Information services Teleconferencing Cellular telephone

Categories of standards Standards De jureDe facto

Standards  De jure standards  Are legislated by an officially recognized body  De facto standards  Proprietary Originally invented by a commercial organization on a basis for the operation of its products.  Non-proprietary Originally developed by groups or committees that have passed them into the public domains; also called open standards.

Standards Organization Standards are essential in creating and maintaining an open and competitive market for equipment manufacturers and also in guaranteeing national and international interoperability of data and telecommunications technology. Developed by cooperation among -  Standards creation committee  Forums  Govt. regulatory agencies

STANDARDS ORGANIZATIONS Standards are developed through cooperation of standards creation committees. Standard Creation Committees  International Standards Organization(ISO), 1947:  The ISO is a multinational body whose membership is drawn mainly from the standards creation committees of various governments throughout the world.  The ISO’s efforts in the field of information technology, which have resulted in the creation of the Open Systems Interconnection(OSI)model for network communications.  International Telecommunications Union-Telecommunication Standards Sector(ITU-T).:  By the early 1970s a number of countries were defining national standards for telecommunications.  The United Nations responded by forming, as part of its International Telecommunications Union(ITU), a committee, the Consultative Committee for International Telegraphy and Telephony(CCITT).  On March 1, 1993, the name of this committee was changed to the International Telecommunications Union-Telecommunication Standards Sector(ITU-T).

 American National Standards Institute(ANSI):  ANSI,s expressed aims include serving as the national coordinating institution for voluntary standardization in the United States, furthering the adoption of standards as a way of advancing the U.S. economy, and ensuring the participation and protection of public interests.  Institute of Electrical and Electronics Engineers(IEEE).  It aims to advance theory, creativity, and product quality in the fields of electrical engineering, electronics, and radio as well as in all related branches of engineering.  The IEEE oversees the development and adoption of international standards for computing and communication.  Electronic Industries Association(EIA)  The EIA has made significant contributions by defining physical connection interfaces and electronic signaling specifications for data communication.

Introduction Forums  Frame Relay Forum.: It was formed by Digital Equipment Corporation, Northern Telecom, Cisco, and StaraCom to promote the acceptance and implementation of frame relay. The forum’s results are submitted to the ISO.  ATM Forum: The ATM Forum promotes the acceptance and use of Asynchronous Transfer Mode(ATM) technology. The ATM forum is made up of vendors of hardware and software that support ATM. Regulatory Agencies  Federal Communications Commission(FCC): The FCC has authority over interstate and international commerce as it relates to communications.

 QUIZ  Which organization consists of computer scientists and engineers and is known for its development of LAN Standards a. EIA b. ITU-T c. ANSI d. IEEE

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

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. Distributed Processing Network Criteria Physical Structures Network Models Categories of Networks Interconnection of Networks: Internetwork Topics discussed in this section:

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

1.22 Figure 1.4 Categories of topology

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

1.24 Figure 1.6 A star topology connecting four stations

1.25 Figure 1.7 A bus topology connecting three stations

1.26 Figure 1.8 A ring topology connecting six stations

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

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

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

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