Introduction to Computer Networks Tuesday, April 25, 2017 Introduction to Computer Networks Tuesday, April 25, 2017 1.#

Tuesday, April 25, 2017 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. Tuesday, April 25, 2017 1.#

Overview Tuesday, April 25, 2017

Where are the data communications? Why data communications? Tuesday, April 25, 2017 DATA COMMUNICATIONS Where are the data communications? Why data communications? Telecommunication: communication at a distance. Data: information presented in whatever form is agreed upon by the parties creating and using the data. Data communications: the exchange of data between two devices via some form of transmission medium such as a wire cable. Tuesday, April 25, 2017 1.#

Four fundamental characteristics: Tuesday, April 25, 2017 DATA COMMUNICATIONS What do we need? Hardware Software Four fundamental characteristics: Delivery: correct destination Accuracy: correct data Timeliness: fast enough Jitter: uneven delay Tuesday, April 25, 2017 1.#

Topics to be covered: Components Data representation Data flow Tuesday, April 25, 2017

Components Figure 1.1 Five components of data communication Tuesday, April 25, 2017 Components Figure 1.1 Five components of data communication Tuesday, April 25, 2017 1.#

Communication Tasks Transmission system utilization Interfacing Some of the key tasks that must be performed in data communication system. Transmission system utilization Interfacing Synchronization Error Detection & Correction Flow control Addressing Routing Recovery Message formatting Security Network Management Tuesday, April 25, 2017

Data Representation Text Numbers Direct conversion Images Audio Video Tuesday, April 25, 2017 Data Representation Text Email, articles, etc Coding (Unicode, ASCII) Numbers Direct conversion Images Pixels, resolution, gray scale, RGB. Audio Continuous, signal conversion Video Movie, continuous/discrete Tuesday, April 25, 2017 1.#

Data Flow Figure : Data flow (simplex, half-duplex, and full-duplex) Tuesday, April 25, 2017 Data Flow Tuesday, April 25, 2017 Figure : Data flow (simplex, half-duplex, and full-duplex) 1.#

Topics to be covered: Distributed Processing Network Criteria Physical Structures Network Models Categories of Networks Internetwork Tuesday, April 25, 2017

Task is divided among multiple computers. Tuesday, April 25, 2017 Task is divided among multiple computers. Advantages of Distributed processing Security/Encapsulation Distributed Database Faster problem solving Security through redundancy Tuesday, April 25, 2017 1.#

NETWORKS Network criteria Performance Transit time, response time. Tuesday, April 25, 2017 NETWORKS Network criteria Performance Transit time, response time. Throughput, delay. Reliability Failure frequency, recovery time Security Protection. Tuesday, April 25, 2017 1.#

Tuesday, April 25, 2017 Type of Connections 1.Spatially shared 2.Time shared Figure : Types of connections: point-to-point and multipoint Tuesday, April 25, 2017 1.#

Physical topology Figure : Categories of physical topology Tuesday, April 25, 2017 Physical topology Figure : Categories of physical topology Tuesday, April 25, 2017 1.#

Mesh Networks Fully Mesh A B C D E Partial Mesh A B C D E Tuesday, April 25, 2017 Mesh Networks Fully Mesh A B C D E Partial Mesh A B C D E Things to bring out: How do you get from A to B in the partial mesh? There is more than one answer. Which is the shortest route and which is the longest route? Important points – You need a method of identifying recipient of the information. They might like to know who sent it as well. The intermediate systems might also like to know where the information should go! In the full mesh there is always a route to everywhere else, even if there is one fault. Can you say the same for the partial mesh shown above? What about security? A must trust D, E and C or at least some of them to get the message through. Tuesday, April 25, 2017 1.#

Star Figure : A star topology connecting four stations Tuesday, April 25, 2017 Star Figure : A star topology connecting four stations Tuesday, April 25, 2017 1.#

Bus Figure : A bus topology connecting three stations Tuesday, April 25, 2017 Bus Figure : A bus topology connecting three stations Tuesday, April 25, 2017 1.#

Ring Figure : A ring topology connecting six stations Tuesday, April 25, 2017 Ring Figure : A ring topology connecting six stations Tuesday, April 25, 2017 1.#

Classification of Networks by Size and Community A city wide network: area inside a town or city; TV cables. A company or home: covers few km, 100-1000 mbps A country wide network: long distance transmission

Single to Multiple LANs Tuesday, April 25, 2017

Tuesday, April 25, 2017 Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet Tuesday, April 25, 2017 1.#

Metropolitan Area Network Tuesday, April 25, 2017

Wide Area Network Tuesday, April 25, 2017

Internetworking When two or more networks are connected , they become an internetwork, or internet . The term internet means interconnection of network While the Internet is the name of a specific worldwide network. Tuesday, April 25, 2017

Tuesday, April 25, 2017 THE INTERNET The Internet has revolutionized many aspects of our daily lives. It has affected the way we do business as well as the way we spend our leisure time. The Internet is a communication system that has brought a wealth of information to our fingertips and organized it for our use. Tuesday, April 25, 2017 1.#

The Internet Today’s Internet Hierarchical Infrastructure International/National ISPs Connected by NAP – Network Access Points (also called peering points Or Internet eXchanges) Regional ISP (Local) ISP ISP = Internet Service Provider Tuesday, April 25, 2017

PROTOCOLS AND STANDARDS Tuesday, April 25, 2017 PROTOCOLS AND STANDARDS Protocols (rules) Why do we need protocols? Key elements of protocols Syntax Semantics Timing Standards De facto (by fact) vs. De jure (by law) Organizations Internet standards (Internet draft & RFC) Tuesday, April 25, 2017 1.#

PROTOCOLS AND STANDARDS Tuesday, April 25, 2017 PROTOCOLS AND STANDARDS Network Standards Organizations National Standards Organizations (Generally responsible for standards within a nation and usually participate in that nation’s international activity) • American National Standards Institute (ANSI) • British Standards Institute (BSI) • French Association for Normalization (AFNOR) • German Institute for Normalization (DIN) Regional Standards Organizations (Restrict their activity to a specific geographical region but generally influence standards outside their regions) • Committee of European Posts and Telegraph (CEPT) • European Committee for Standardization (CEN) • European Computer Manufacturers’ Association (ECMA) International Standards Organizations (Promote standards for worldwide use) • International Standards Organization (ISO) • International Telecommunications Union (ITU)consists of ITU-T, which is responsible for communications, interfaces, and other standards related to telecommunications; and ITU-R, which is responsible for allocating frequency bands in the electromagnetic spectrum for telecommunications, and for making recommendations relating to radio communications. (Note: ITU-T is the former CCITTConsultative Committee for International Telephony and Telegraphy.) Industry, Trade, and Professional Standards Organizations (Restrict their activity to member interest areas but generally influence other areas) • Electronic Industries Association (EIA) • Telecommunications Industries Association (TIA) • Institute for Electrical and Electronics Engineers (IEEE) • Internet Engineering Task Force (IETF) Tuesday, April 25, 2017 1.#

Summary Data communications Networks The internet Tuesday, April 25, 2017 Summary Data communications Networks The internet Protocols and standards Tuesday, April 25, 2017 1.#