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Introduction to Computer Networks Dr. John P. Abraham INTRODUCTION TO COMPUTER NETWORKS What is covered in the course Network Applications & Network programming Data communications (low level details) Packet switching and network technologies Internetworking with TCP/IP Other concepts such as interoperability standards, protocol suites and layering models Socket programming All underlying network applications such as email, ftp, web, etc. use underlying technologies and programs The goal of this course is not to teach you programming. Students should write three socket programs in a language of their choice Data Communication Technologies used to send data across communication lines Modulation Digital to analog Light Multiplexing Encryption Packet Switching and networking technologies Evolved from telegraph and telephone technologies Mechanical connections are replaced with electronic switches Packet switching – eliminated the need for a dedicated circuit Devices through out the network should have information about how to reach the target destination Takes into account speed, cost, distance and size of packets Internetworking with TCP/IP Tolerance of heterogeneity of underlying technologies. The internet is formed by interconncecting multiple packet-switching networks, as well as public and private networks. Introduction to Computer Networks Applications of Networks Resource Sharing Hardware (computing resources, disks, printers) Software (application software) Information Sharing Easy accessibility from anywhere (files, databases) Search Capability (WWW) Communication Email Message broadcast See next slide Application of network 2 Remote computing Virtualization (see future slided) Supercomputing - used for highly calculation-intensive tasks in quantum physics, genetics, weather modeling, etc. Distributed processing – A program running on top of a network distributes the job. GRID Computing – very similar to distributed. A middleware is used to manage all the computers in the system (see next slide). Cloud computing (see future slide) Grid computing Multiple independent computing clusters which act like a “grid” because they are composed of resource nodes not located within a single administrative domain. Offering online computation or storage (like electricity sale). The creation of a “virtual supercomputer” by using spare computing resources within an organization Virtualization the act of decoupling one computing resource from others without impacting the usability across these resources. User state virtualization Application virtualization. Client-Hosted Desktop virtualization Server-based Desktop virtualization Application Virtualization User state virtualization. separates the user data and settings from any PC and enables IT to store them centrally (i.e., in the datacenter) while also making them accessible on any PC. It also simplifies the central backup of user data since data is already stored centrally on servers. Application virtualization Isolates applications from each other and solves application to application compatibility issues by allowing applications to run together even though they may require the same resources from the OS Application virtualization allows IT to store the application centrally and stream the application to a desktop based on user access. Client-Hosted Desktop Virtualization. technology (such as Microsoft® Virtual PC or Sun xVM Virtual Box ) that separates the operating system from the physical hardware and allows a single PC to run virtual machines side by side with the host OS. Server-Based Desktop Virtualization: Allows the execution of an environment at one place and presentation of that environment or user interface at a different location. These technologies usually use remote desktop protocols, such as RDP, to decouple the user interface location from the execution environment location. Remote execution enables organizations to use older PCs as “thin clients,” giving users the benefit of newer applications and versions of Windows while helping save the environment by avoiding the dumping of electronics into landfills. Cloud Computing is location independent computing shared servers provide resources, software, and data to computers. computing is moved away from personal computers or an individual application server to a “cloud” of computers. Users of the cloud only need to be concerned with the computing service being asked for, as the underlying details of how it is achieved are hidden. This method of distributed computing is done through pooling all computer resources together and being managed by software rather than a human. Introduction to Computer Networks Network Components Physical Media Interconnecting Devices Computers Networking Software Applications Introduction to Computer Networks Networking Media Networking media can be defined simply as the means by which signals (data) are sent from one computer to another (either by cable or wireless means). Introduction to Computer Networks Networking Devices HUB, Switches, Wireless Access Modems etc. Routers, Points, Introduction to Computer Networks Computers: Clients and Servers In a client/server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients. The server contains the file, print, application, security, and other services in a central computer that is continuously available to respond to client requests. Introduction to Computer Networks Networking Protocol: TCP/IP Introduction to Computer Networks Applications E-mail Searchable Data (Web Sites) E-Commerce News Groups Internet Telephony (VoIP) Video Conferencing Chat Groups Instant Messengers Internet Radio