Communication Systems PDF

Communication Systems By Dr. Reham Abobeah Evaluation 50 mark Midterm 150 mark 100 mark Final  History of computer Networks Mainframes & Dumb terminals. Disadvant...

Communication Systems By Dr. Reham Abobeah Evaluation 50 mark Midterm 150 mark 100 mark Final  History of computer Networks Mainframes & Dumb terminals. Disadvantages of these systems The financial cost of these systems is very high. Beneficiaries cannot fully utilize these systems. Mini computers/single user Distributed computing or distributed processing. Sneaker net The sneaker net Sneaker Net Disadvantages  The need for a large amount of floppy disks or a set of CD-ROMs or DVDs.  A lot of effort and time are needed, and a high probability of data transfer errors.  If you have one printer and several PCs, you must move the printer & connect to the intended PC, or leave the printer connected to one PC & wait for a long line to print. A printer in a stand-alone environment Due to the disadvantages of these separate individual devices, the best solution was to connect these PCs with each other through a master device that organizes operations between them. OR, the simplest image of ​network using via connecting two computers together through a communication line to transfer data between them. Sharing a printer in a networking environment A simple computer network  These networks were characterized by: 1. Each PC has a separate operation from the main server, [Distributed Processing System (DPS)]. 2. The sub-units in the network are called several names including: (client - end user - node - work station - agent - host). 3. Networks can do many tasks, including: Store and retrieve files, sharing Resources, manage users, Security because each subnet has user name and password.  General definition of networks A network is a set of electronic devices connected to each other for the purpose of sharing information and services.  Definition of computer networks Computer Network is a communication system developed to connect a variety of different computers with each other by means of connecting units (NIC), transmission media (Cables) and Network devices (Repeaters – Routers – Bridge). Sharing a printer in a networking environment Connect the bridge devices in a common way  COMPONENTS OF COMPUTER NETWORK  Two or more computers (clients & servers PCs)  A network interfacing card(NIC) for each PC.  Software called operating system (OS)  Transmission Media (Cables) as links between the PCs (twisted pair, Coaxial, Fiber optics).  Peripherals or shared resources (Storage units, printers, Fax).  Network Devices for connecting the desired network (Hubs, Repeaters, Bridges, Switches).  FILE SHARING – Networks offer a quick and easy way to share files directly.  RESOURCE SHARING – All computers in the network can share resources such as printers, fax machines, scanners, and modems.  COMMUNICATION –Those on the network can communicate with each other via e-mail, instant messages, etc.  Flexible Access - Networks allow their users to access files from computers throughout the network.  Sharing of Information - Computer networks enable us to share data and information with the computers that are located geographically large distance apart.  The different types of network are based on following:  Size of the network– Refers to thearea over which the network is spread.  Connection – Refers to the transmission media and protocols used for connecting.  Network topology – Arrangement of computers on the network. ON THE BASIS OF SIZE ON THE BASIS OF SIZE 1. LAN A local area network (LAN) is a data communication system that allows a number of independent devices (PCs) to communicate with each other and share the network resources such as printer, fax, files storage devices, and application programs. It is distinguished from other types of data networks in that the communication is usually confined to small/moderate-size geographical area such a single office, or LAB. LAN runs at a speed of either 10 / 100 / 1000 Mbps, and has low delays. A LAN based on wireless technology is called wireless local area network(WLAN).  LAN Characteristics:  Sharing Resources (Scanners, printers, application programs)  Allowing the communication between users(E-mail)  Short distance span: LAN connects computers in a small area like a room, LAB, office, or a campus spread up to a few meters.  Low error rate and high reliability.  Narrowly owned (usually a single private owner)  Ensuring the compatibility between different manufacture- equipments. ON THE BASIS OF SIZE 2. METROPOLITAN AREA NETWORK (MAN)  MAN is a computer network which connects several LAN spread over a city. This network is used to connect several offices in different building in closed area.  For example, faculty of Engineering consists of several departments, each department is in a building, and all buildings are in one place. It covers the distance upto 3 0 - 5 0 km. ON THE BASIS OF SIZE 3.WIDE AREA NETWORK (WAN) WAN is a network that connects computers over long distances like cities, countries, continents or world wide. It allows users to have real-time communication capabilities with other users. It is slower and less reliable than a LAN. INTERNET is a common example of WAN. Differentiate between the types of computer networks, LAN, MAN, and WAN?  Types of LANs LOCAL AREA NETWORK PEER TO PEER NETWORK CLIENT SERVER NETWORK P2P NETWORK  In p2p network, each computer can function as both client and server.  i.e. All PCs are equal in their importance in the network, thus PCs are called peers.  Network resources (scanner, printers, app programs) are distributed among PCs.  Each computer is responsible for making its own resources available to other computers on the network.  Each computer is responsible for setting up and maintaining its own security for these resources.  Each computer is responsible for accessing the required network resources from peer to peer relationships.  It is useful for a small network containing less than 10 computers on a single LAN.  P2P networks  Pros.  In this network, no need to server or network administrator, but it is easy to set up and provide file sharing and printer sharing.  Cons. o This network isn’t useful in security, backup, database apps, large networks. CLIENT-SERVER NETWORK  In client-server network, every PC performs only one job: client or server (but not both jobs)  A server is simply a computer that contains all the network resources and provides and is responsible for all client requests.  A client is a computer running a program that requests the service from a server.  LAN is based on client-server network.  A client-server network , all available network resources such as files, directories, applications and shared devices, are centrally managed and hosted by the server and then are accessed by client.  In Client serve network, servers provide security and administration to the network. TYPES OF SERVERS  TYPES OF SERVERS  File server: provides the services for storing, retrieving and moving the data.  A user can read, write, exchange and manage the files with the help of file servers.  Printer server: controls and manages printing on the network. It also offers the fax service to the network users.  Application server: The expensive software & additional computing power can be shared by the computers in a network with he help of application servers.  Message server: It is used to co-ordinate the interaction between users, documents and applications. The data can be used in the form of audio, video, binary, text or graphics.  Database server: It is a type of application server. It allows the users to access the centralized strong database. Differentiate between peer to peer and client server networks? AnyQuestions?