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Text Book 1. Computer Networks & Internets by Douglas E Comer. 2. Data and Computer Communication by William Stalling, 5th or above edition. 2
Marks distribution Topic no First Mid 20 1,2,3 Second Mid 20 4,5,6 Seminar 10 Selected topics Quizzes/assignment 10 Based on taught topics Final Exam 40 all topics 3
Studying networks because ; The world is interconnected Applications now operate in a distributed environment 4
Topics of this subject 5 Network definition and basic Terminology Network Data Transmission Modes & data Transmission Mediums Network Topologies and technologies Network Devices Switching Techniques. Architecture (OSI & TCP/IP reference Model ) Client Server Architecture. Internet & Its Related Terminology (IP Addressing).
Networks A network is a set of devices at least two (often referred to as nodes-hosts-enduser) 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. 6
Importance of Networks Software and file sharing Hardware sharing Modern Technologies (IP Telephony, Video Conferencing) 7
Depending on one s perspective, we can classify networks in different ways; Based on transmission media: Wired (UTP, coaxial cables, fiber-optic cables) and Wireless Based on network size: LAN and WAN (and MAN) Based on management method: Peer-to-peer and Client/Server Based on topology (connectivity): Bus, Star, Ring 8
Network Criteria Performance Reliability Security 9
Performance Depends on a number of factors. number of users type of transmission medium(data rate) hardware software : error-free delivery Evaluated by two networking metrics: Throughput and Delay. 10
Reliability Frequency of failure Recovery time of a network after a failure Catastrophe Networks must be protected from catastrophic events such as fire, earthquake, or theft. Security Protecting data from Unauthorized access 11 Protecting data from Viruses and Worms
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. 12
The effectiveness of a data communication system depends on three fundamental characteristics Delivery must deliver data to the correct destination (the intended device or user) Accuracy must deliver data accurately Timeliness must deliver data in a timely manner 13 Jitter Refers to the variation in the packet arrival time.
14 Data communication system components
Five components of data communication Message is the information(data) to be communicated. (text, numbers, pictures, sound, video or any combination of these). A group of bits are used to represent a character/number/special symbol/control Characters Sender is the device that sends the data message. (computer, workstation, telephone handset, video camera) Receiver 15 is the device that receives the message. (computer, workstation, telephone handset, video camera)
Medium is the physically path by which a message travels from sender to receiver. (twisted pair wire, coaxial cable, fiber- optic cable, laser, or radio waves(terrestrial or satellite microwave) Protocol is a set of rules that govern data communication. It represents an agreement between the communicating devices. Without a protocol, two devices may be connected but not communicating 16
Direction of Data Flow is used to define the direction of signal flow between two link devices Simplex Half-Duplex Full-Duplex 17
Simplex Half Duplex Full Duplex 18
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. Keyboards and traditional monitors are examples of simplex devices. The keyboard can only introduce input; the monitor can only accept output. The simplex mode can use the entire capacity of the channel to send data in one direction. 19
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. The half-duplex mode is like a one-lane road with traffic allowed in both directions. When cars are traveling in one direction, cars going the other way must wait. In a half-duplex transmission, the entire capacity of a channel is taken over by whichever of the two devices is transmitting at the time. 20
Full Duplex In full-duplex mode, both stations can transmit and receive simultaneously. The full-duplex mode is like a two way street with traffic flowing in both directions at the same time. One common example of full-duplex communication is the telephone network. When two people are communicating by a telephone line, both can talk and listen at the same time. 21