Computer Communication and Networks Lecture 1 PDF

Computer Communication and Networks Lecture 1 1 McGraw-Hill ©The McGraw-Hill Companies, Inc., 2000 Course Information Course Code: CEN303 C...

Computer Communication and Networks Lecture 1 1 McGraw-Hill ©The McGraw-Hill Companies, Inc., 2000 Course Information Course Code: CEN303 Course Name Computer Communication and Networks Course Objective: Describe the key terminologies and technologies of computer networks, Explain the services and functions provided by each layer in the Internet protocol stack, Identify various internetworking devices and protocols, and their functions in a network, Analyze working and performance of key technologies, algorithms and protocols. Build Computer Network on various Topologies 2 Marks Distribution Assignments ……………..……….………10% Quiz ……….……………………………..…10% Class Participation (Notes).……….….05% Lab and Project ………….……………...15% Mid Term…………………..………….……20% Final Term ………...…………………......40% 3 Prerequisites Required: Introduction to Computing Good knowledge of Computers Recommended: Basic Computer Programming Concepts Course Material Reference books Data Communications & Networking, 5th edition by Behrouz A. Forouzan  Evaluation Date Topics Signature Lecture Instrument Used Week 1 Data Communication concepts, Network topologies and the physical layer r Bus 1 topology, ring topology, star topology Week 2 Analogue and digital Transmission, Transmission Media and Transmission 2 Technologies Noise, Encoding, Asynchronous and Synchronous transmission Week 3 Network Models, system architectures (OSI, TCP/IP) Quiz#1 3 Assignment-1 4 Week 4 Error Control, Flow Control High-Level Data Link Control (HDLC Week 5 Data Link Protocols, Bridging, Connection-Oriented, Transport Protocol Mechanisms 5 TCP l UDP 6 Week 6 Local Area Networks and MAC Layer protocols Week 7 Multiplexing Frequency-Division Multiplexing Synchronous asynchronous Quiz#2 7 communication , Time-Division Multiplexing Statistical Time-Division Multiplexing Assignment-2 8 Week 8 Review 9 Week 9 Mid term Week 10 Switched and IP Networks ,IP Sub netting, IP Classes Class A Class B and Class C 10 IP’s 11 Week 11 Inter-networking Multicasting broad cast and unicast Week 12 Routing Protocols RIP Quiz#3 12 Assignment-3 13 Week 13 Transport layer protocols TCP, UDP and SCTP Week 14 Application Layer Protocols Remote login to hosts: Telnet. 14 File transfer: File Transfer Protocol (FTP), Trivial Week 15 File Transfer Protocol (TFTP) 15 Electronic mail transport: Simple Mail Transfer Protocol (SMTP) Week 16 16 Wireless LANs, Wireless LAN Technology IEEE 802.11 Architecture and Services Week 17 Review and Project Presentation 17 Project 18 Week 18 Final Term  Chapter 1 Introduction 1.7 Computer Communication & Networks Overview of Lecture 1 Data Communication Brief History of Communication Data Communication System Key Data Communication Terminology DATA COMMUNICATION DEFINITION “Data Communication is the exchange of Information from one entity to the other using a Transmission Medium” History of Data Communication Telegraph 1837 Samuel Morse Telephone 1876 Alexander Graham Bell By 1950’s 1970’S Today How Telegraph Works 11 How telegraph Works Data Communication Definition (Modified) “Data Communication is the exchange of data (in the form of 0’s and 1’s) between two devices (computers) via some form of the transmission medium.”  LOCAL and REMOTE Communication  LOCAL – Communicating devices are present in the same building or a similarly restricted geographical area  LOCAL and REMOTE Communication  REMOTE – Communicating devices are present farther apart  Data Communication System  For Data Communication to occur, communicating devices must be a part of a system made up of some specific kind of hardware and software. This system is known as “DATA COMMUNICATION SYSTEM”  Effectiveness of Data Comm. System Effectiveness of data communication system depends on: 1. Delivery : The system must deliver data to correct destination. Data received by the indented user only 2. Accuracy: The system must deliver data accurately (no change). Data changed & uncorrected is unusable 3. Timeliness: The system must deliver data in timely manner Data arrived late are useless In the same order (video and audio) & without delay (Real time transmission) 4. Jitter: Variation in the packet arrival time (uneven quality in the video is the result) Components of a Simple Data Communication System  Components of a Data Communication System A Data communication system is made up of 5 components: Message Sender Receiver Medium Protocol Components 1. Message: the information (data) to be communicated – Consist of text, numbers, pictures, audio, or video 2. Sender: the device that sends the data message – Computer, workstation, telephone handset, video camera, … 3. Receiver: the device that receives the message – Computer, workstation, telephone handset, television,  Transmission Media 4. Medium: The physical path by which a message travels from sender to receiver – twisted pair, coaxial cable, fiber-optic, radio waves Protocol protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt a human protocol and a computer network protocol: time Hi TCP connection req. Hi TCP connection Got the reply. time? Get http://gaia.cs.umass.edu/index.htm 2:00 A Complex Data Comm. System EXAMPLE – Electronic Mail  Figure 1.2 Data flow (simplex, half-duplex, and full-duplex) 1.25  1-2 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. A link can be a cable, air, optical fiber, or any medium which can transport a signal carrying information. Topics discussed in this section:  Network Criteria  Physical Structures  Categories of Networks 1.26  Network Criteria Performance Depends on Network Elements Measured in terms of Delay and Throughput Reliability Failure rate of network components Measured in terms of availability/robustness Security Data protection against corruption/loss of data due to: Errors Protecting data from unauthorized access 1.27  Physical Structures 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 1.28  Figure 1.3 Types of connections: point-to-point and multipoint 1.29  Figure 1.4 Categories of topology 1.30 Physical Topology Mesh Every link is dedicated point-to-point link The term dedicated means that the link carries traffic only between the two devices it connects Physical Topology Mesh To link n devices fully connected mesh has: n ( n - 1) / 2 physical channels (Full-Duplex) Every Device on the network must have n - 1 ports Physical Topology Mesh Example: 8 devices in mesh has links: n(n-1) / 2 number of links = 8 (8-1)/2 = 28 number of ports per device = n – 1 = 8 – 1=7 Physical Topology Mesh Advantages Each connection carry its own data load (no traffic problems) A mesh topology is robust Privacy or security Fault identification and fault isolation Physical Topology Mesh: Disadvantages Big amount of cabling Big number of I/O ports Installation and reconnection are difficult Sheer bulk of the wiring can be greater than the available space Hardware connect to each I/O could be expensive Mesh topology is implemented in a limited fashion; e.g., as backbone of hybrid network Physical Topology Star: Dedicated point-to-point to a central controller (Hub) No direct traffic between devices The control acts as an exchange Physical Topology Star Advantages Less expensive than mesh (1 Link + 1 port per device) Easy to install and reconfigure Less cabling Additions, moves, and deletions required one connection Robustness : one fail does not affect others Easy fault identification and fault isolation Physical Topology Star Disadvantages Dependency of the whole topology on one single point (hub) More cabling than other topologies ( ring or bus) Used in LAN Physical Topology Bus It is multipoint One long cable acts as a backbone Used in the design of early LANS, and Ethernet LANs Physical Topology Bus Nodes connect to cable by drop lines and taps Signal travels along the backbone and some of its energy is transformed to heat Limit of number of taps and the distance between taps Physical Topology Bus Advantages Ease of installation Less cables than mesh, star topologies Disadvantages Difficult reconnection and fault isolation ( limit of taps) Adding new device requires modification of backbone Fault or break stops all transmission The damaged area reflects signals back in the direction of the origin, creating noise in both directions Physical Topology Ring Each device has dedicated point-to-point connection with only the two devices on either side of it A signal is passed along the ring in one direction from device to device until it reaches its destination Each devices incorporates a Repeater Physical Topology Ring Advantages Easy of install and reconfigure Connect to immediate neighbors Move two connections for any moving (Add/Delete) Easy of fault isolation Disadvantage Unidirectional One broken device can disable the entire network. This weakness can be solved by using a dual ring or a switch capable of closing off the break Hybrid Topology Hybrid networks use a combination of any two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network connected to a tree network is still a tree network topology. A hybrid topology is always produced when two different basic network topologies are connected. Two common examples for Hybrid network are: star ring network and star bus network.  Figure 1.9 A hybrid topology: a star backbone with three bus networks 1.45  Categories of Networks Local Area Networks (LANs) Short distances Designed to provide local interconnectivity Wide Area Networks (WANs) Long distances Provide connectivity over large areas Metropolitan Area Networks (MANs) Provide connectivity over areas such as a city, a campus 1.46  Figure 1.10 An isolated LAN connecting 12 computers to a hub in a closet 1.47  Figure 1.11 WANs: a switched WAN and a point-to-point WAN 1.48  Figure 1.12 A heterogeneous network made of four WANs and two LANs 1.49  1-3 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. Topics discussed in this section: Organization of the Internet Internet Service Providers (ISPs) 1.50  Figure 1.13 Hierarchical organization of the Internet 1.51  1-4 PROTOCOLS A protocol is synonymous with rule. It consists of a set of rules that govern data communications. It determines what is communicated, how it is communicated and when it is communicated. The key elements of a protocol are syntax, semantics and timing Topics discussed in this section:  Syntax  Semantics  Timing 1.52  Elements of a Protocol Syntax Structure or format of the data Indicates how to read the bits - field delineation Semantics Interprets the meaning of the bits Knows which fields define what action Timing When data should be sent and what Speed at which data should be sent or speed at which it is being received. 1.53 1.54