Lecture 2: Computer Networks PDF

Lecture # 2 Computer Networks -1 Dr.Abdelaziz.Mohamed 1  Overview This chapter covers: – Computer network is defined – Common networking and communications applications – Networking concepts and terminology – Technical issues related...

Lecture # 2 Computer Networks -1 Dr.Abdelaziz.Mohamed 1  Overview This chapter covers: – Computer network is defined – Common networking and communications applications – Networking concepts and terminology – Technical issues related to networks, including general characteristics of data transmission, and types of transmission media in use today – Explanation of the various communications protocols and networking standards – Various types of hardware used with a computer network 2  What Is aNetwork? Network – A connected system of objects or people Computer network – A collection of computers and other hardware devices connected together so users can share hardware, software, and data, and electronically communicate Computer networks are converging with telephone and other communications networks Networks range from small private networks to the Internet In most businesses, computer networks are essential 3  NetworkingApplications Cellular (cell) Phones – Must be within range of cell tower to function Dual-mode Phones – Allow users to make telephone calls using more than one communications network – Cellular/Wi-Fi dual-mode phones can switch seamlessly between the Wi-Fi network and a cellular network Satellite Phones – Communicate via satellite technology – Most often used by individuals such as soldiers, journalists, wilderness guides, and researchers 4  Networking Applications Television and Radio Broadcasting – Still used to deliver TV and radio content to the public – Other networks involved with television content delivery are cable TV networks, satellite TV networks, and private closed-circuit television systems Global Positioning System (GPS) Applications – Uses satellites and a receiver to determine the exact geographic location of the receiver – GPS receivers: Commonly used by individuals to determine their geographic location 5  Networking Applications Monitoring Systems – Use networking technology to determine the current location or status of an object RFID-based Systems – Monitor the status of objects GPS-based Monitoring Systems – Monitor the physical location of objects – Vehicle and child monitoring systems Electronic Medical Monitors – Home healthcare 6  Networking Applications Multimedia Networking – Distributing digital multimedia content, typically via a home network – Necessary networking capabilities are often built into devices being used – Might need to use multimedia networking device such as digital media receiver or digital media streamer – Place shifting Content:Allows individuals to view multimedia content at a more convenient location, i.e., Slingbox Sensors are used in some monitoring systems – Sensor networks Home automation (smart thermostats, etc.) 7  Networking Applications Videoconferencing, Collaborative Computing, and Telecommuting – Videoconferencing Use of computers, video cameras, microphones, and networking technologies to conduct face-to-face meetings over a network – Telepresence Videoconferencing A setup that more closely mimics a real-time meeting environment 8  Networking Applications Telemedicine – Use of networking technology to provide medical information and services – Remote monitoring and consultations – Remote diagnosis – Telesurgery Robot assisted surgery where doctor’s physical location is different from the patient’s and robot’s Will be needed for long-term space exploration 9  Network Characteristics Wired vs. Wireless Networks – Wired : A network in which computers and other devices are physically connected to the network with cables Found in schools, businesses, and government facilities – Wireless :A network in which computers and other devices are connected to the network without physical cables Data is typically sent via radio waves Found in homes, schools, and businesses 10  Network Characteristics Network Topologies: Indicate how the devices in the network are arranged – Star Networks All networked devices connect to a central device/server If the central device fails, the network cannot work – Bus Network Uses a central cable to which all network devices connect – Mesh network Multiple connections among the devices on the network so that messages can take any of several possible paths 11 Network Characteristics 12 Network Characteristics 13  NetworkCharacteristics – Peer-to-Peer (P2P) Networks Central server is not used All computers on the network work at the same functional level Users have direct access to the computers and devices attached to the network Less complicated and less expensive to implement than client- server networks Internet P2P Computing – Content is exchanged over the Internet directly between users 14  Network Characteristics Network Size and Coverage Area – Personal Area Networks (PANs) Connect an individual’s personal devices – Devices must be physically located close together – Local Area Networks (LANs) Connect devices located in a small geographic area – Metropolitan Area Networks (MANs) Cover a metropolitan area such as a city or county – Wide Area Networks (WANs) Cover a large geographic area Two or more LANs connected together 15  Network Characteristics – Intranets and Extranets Intranet :Private network designed to be used by an organizations’ employees; set up like the Internet Extranet : Company network accessible by authorized outsiders – Virtual Private Networks (VPNs) Private, secure path over the Internet that provides authorized users a secure means of accessing a private network via the Internet Uses tunneling and special encryption technology 16  Quick Quiz 1. Which of the following describes a group of private secure paths set up using the Internet? a. VPN b. WAN c. WSN 2. True or False: With a bus network, all devices are connected directly to each other without the use of a central hub or cable. 3. A private network that is set up similar to the World Wide Web for use by employees of a specific organization is called a(n). Answers: 1) a; 2) False; 3) intranet 17  DataTransmission Characteristics Transmission Type and Timing – Serial Data sent one bit at a time, one after another, along a single path – Parallel Data sent at least one byte at time with each bit in the byte taking a different path 18  DataTransmission Characteristics Synchronous Transmission – Blocks of data are transferred at regular, specified intervals – Most data transmissions within a computer and over a network are synchronous Asynchronous Transmission – Data is sent when ready without being synchronized – Start bits and stop bits used to identify the bits that belong in each byte Isochronous Transmission – Data sent at the same time as other, related, data 19 DataTransmission Characteristics 20  DataTransmission Characteristics Simplex Transmission – Data travels in a single direction only Half-Duplex Transmission – Data travels in either direction but only one way at a time Full-Duplex Transmission – Data travels in both directions at the same time Delivery Method – Circuit-Switching – Packet-Switching – Broadcasting 21 DataTransmission Characteristics 22  Summary Networking Applications Network Characteristics Data Transmission Characteristics Networking Media Communications Protocols and Networking Standards Networking Hardware 23