Data Communication and Computer Networks

CHAPTER 1 Data Communication and Computer Networks 1  What is data communication? Data communication is the process of transferring data from one place to another or between two locations. It allows electronic and digital data to move between two...

CHAPTER 1 Data Communication and Computer Networks 1  What is data communication? Data communication is the process of transferring data from one place to another or between two locations. It allows electronic and digital data to move between two networks, no matter where the two are located geographically, what the data contains, or what format they are in. A common example of data communication is connecting your laptop to a Wi-Fi network. This action requires a wireless medium to send and receive data from remote servers. 2 Cont… Communication: sharing information. Sharing can be local (face to face) or remote (over distance) telecommunication (tele: far) means communication at a distance (telephone, television, telegraphy). 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. Communicating devices : made up of : H.W( physical equipments )and S.W 3  Computer Networks A network is a set of devices connected by communication links. A network is simply two or more computers that are linked together. A node can be a computer, printer, or any other device capable of sending and receiving data generated by other nodes on the network 4  Computer Network Applications They provide numerous advantages: Resource sharing such as printers and storage devices Exchange of information by means of e-mails and FTP Information sharing by using Web or Internet Interaction with other users using dynamic web pages Video conferences Parallel computing Instant messaging 5  Types of Computer networks Networks can be classified into several types based on Geographical span -LAN, MAN and WAN Administration -Private network & public network Architecture-Client/Server & peer-to-peer A private network is used inside an organization. 6  Types of Network- Geographical Span 1.LAN (Local Area Network) Local Area Network is generally privately owned that links the devices in a single office, building, or campus. Its size is limited to a few kilometers. It is designed to allow resources to be shared between personal computers or workstations. In general a given LAN will use only one type of transmission medium. The most common LAN topologies are bus, ring, and star. 7  2.MAN(Metropolitan Area Network) A metropolitan area network (MAN) is a network with a size between a LAN and a WAN. A company can use MAN to connect the LANs in all its offices throughout a city. It normally covers the area inside a town or a city. MAN-is A network that is larger than a LAN and connects clients and servers from multiple buildings. Because of the distance it covers, a MAN may use different transmission technology and media than a LAN. 8  Uses of MAN Some common uses of a MAN are: Data and resource sharing among different locations in a city or metropolitan area. It is used to connect different LAN in a city or metropolitan area. It is used to delivering broadband services such as internet access, telephony and video conferencing. Providing centralized data processing and storage facilities. Supporting real-time data and video applications. It is used to connect remote offices to the main corporate network. 9  WAN(Wide Area Network) A wide area network (WAN) provides long-distance transmission of data, image, audio, and video information over large geographic areas that may comprise a country, a continent, or even the whole world. The largest and most varied WAN in the world is the Internet. It is used to connects all the company’s computers and devices, allowing them to share information and resources. 10  Uses of WAN It is used to sharing the resources such as printers and servers among multiple locations. It is used to facilitating, communication and collaboration between employees, customers and partners of the company. It is used to providing remote access to business applications and data. It is used to delivering internet access, VPN ( Virtual Private Network) services and other managed network services. Enabling the transfer of large data files and multimedia content. 11  Types of Network-Architecture Computers can be positioned on a network in different ways relative to each other. They can have different levels of control over shared resources. They can also be made to communicate and share resources according to different schemes. The following sections describe two fundamental network models: peer-to-peer and client/server. 12  Peer-to-Peer peer-to-peer network:- is the simplest form of a network architecture There are no dedicated servers. There is no hierarchy among the computers. All the computers are equal and therefore are known as peers. Each computer functions as both a client and a server. There is no administrator responsible for the entire network. Every computer is capable of sending and receiving information to and from every other computer. 13 Peer-to-Peer Networks 14  Client/Server Networks A network that uses a server to enable clients to share data, data storage space, and devices is known as a client/server network. Client—A computer on the network that requests resources or services from another computer on a network. Clients usually take the form of personal computers, also known as workstations. Every computer on a client/server network acts as a client or a server. Clients on a client/server network do not share their resources directly with each other, but rather use the server as an intermediary. 15  Cont…. Server—A computer on the network that manages shared resources; servers usually have more processing power, memory, and hard disk space than clients. To function as a server, a computer must be running an NOS (network operating system). An NOS: is a special type of software designed to do the following: Manage data and other resources for a number of clients. 16 Ensure that only authorized users access the network.   Restrict when and from where users can access the network. Dictate which rules computers will use to communicate. Supply applications to clients. Examples of NOS: UNIX and Linux, Microsoft Windows Server 2003 or Server 2008, and Mac OS X Server. 17 Client/Server Networks 18  Specialized Servers 1-File Servers :File servers offer services that allow network users to share files. 2- Print Servers :Allow users to share printers. Allow multiple and simultaneous access to printing facilities. 3- Database Servers :Database server can provide a network with powerful database services. 4 -Application Servers :Servers store vast amounts of data that is organized to make it easy to retrieve. An application server differs from a file server in that with file server the data or file is downloaded to the computer which making the request. With an application server, the database /file stays on the server and only the results of a request are downloaded to the computer which making the request. 19 Cont… 5-Mail Servers Mail servers - separate server and client applications. 6-Web Servers :Stores different web pages. 7- Proxy Server : implements Internet connectivity and network security for an entire organization. 20 21  Network Internet and Intranet Internet:is used to connect the different network of computers simultaneously. It is public network, therefore any one can access the internet It provide unlimited information to the users Multiple user It is unsafe Intranet:is type of internet that is used privately It is private network anyone can’t access the internet Limited number of users Provide a piece of limited information to users safe 22  Hardware component of Network Network hardware: is defined as a set of physical or network devices that are essential for interaction and communication between hardware units operational on a computer network 1.NIC(Network Interface Card):is a network adapter used to connect the computer to the network. It is installed in the computer to establish a LAN. It has a unique ID that is written on the chip, and it has a connector to connect the cable to it. The cable acts as an interface between the computer and the router or modem. 23  Types of NIC Wired NIC: Cables and Connectors use Wired NIC to transfer data. Wireless NIC: These connect to a wireless network such as Wifi, Bluetooth, etc 2. HUB: is a multi-port repeater 3. Router: is a device like a switch that routes data packets based on their IP addresses. The router is mainly a Network Layer device 4. Modem: is a short form of Modulator/Demodulator 5. Switch 24 25 26  Software Components of Network Network Software: is mainly focused on reducing design issues like managing, improving, or deploying a network. It helps network administrators to manage a network and prevents unauthorized access and various cyber-attacks, as by using network software one can restrict access to the network. The two major software used in computer networks are the Operating system and the Protocol suite. 27  Cont… Operating system: function is to support the network. For example, Windows, Mac, and Linux OS can easily connect to a network. Protocol suite consists of layers and each layer is working according to different protocols. 28 The software components of a network include: Application layer: refers to the applications and services running on the network. Control layer: lies at the center of the architecture and defines network topology and traffic routing. Infrastructure layer: physically handles network traffic based on the configuration at the control level. Operating system: software required for installing computer networks. Protocols: set of rules upon which communication devices agree to communicate successfully.. 29  Network Topology is the arrangement with which computer systems or network devices are connected to each other. The topology of a network is the geometric representation of the relationship of all the links and linking devices (usually called nodes) to one another. The topology- is physical layout of a computer network. Topologies vary according to the needs of the organization, available hardware and expertise. 30 31  Bus Topology  A Bus topology consists of single cable –called bus-connecting all nodes on a network without intervening connectivity devices.  A bus topology is multipoint connection.  One long cable acts as a backbone to link all the devices in a network. all devices share single communication line or cable. 32 Advantages Connecting a computer or peripheral to a linear bus is easy. This topology requires least amount of cabling to connect the computers and therefore, less expensive. It is easy to extend a bus since two cables can be joined into longer cable with a connector. Disadvantages Entire network shuts down if there is a failure on the backbone. Heavy traffic can slow down a bus because computers on such networks do not coordinate. 33  Ring Topology In a ring topology, each device has a dedicated point-to-point connection with only the two devices on either side of it. each host machine connects to exactly two other machines, creating a circular network structure. When one host tries to communicate or send message to a host which is not adjacent to it, the data travels through all intermediate hosts. There is no central server. 34 Advantage  Ring topology is easy to install and reconfigure.  Every computer is given equal access to the ring.  Hence, no single computer can monopolize the network. Disadvantages  Failure in any cable or node breaks the loop and can take down the entire network.  Maximum ring length and number of nodes are limited. 35  Star Topology  All hosts in Star topology are connected to a central device, known as hub device, using a point-to-point connection. That is, there exists a point to point connection between hosts and hub.  The hub device can be any of the following:  Layer-1 device such as hub or repeater  Layer-2 device such as switch or bridge  Layer-3 device such as router or gateway  The devices are not directly linked to one another. 36  A star network is designed with each node (file server, workstation, peripheral) connected directly to a central network hub or server 37 Advantages of Star  Star topology is easy to install and wire.  The network is not disrupted even if a node fails or is removed from the network.  Fault detection and removal of faulty parts is easier in star topology. Disadvantages of Star  It requires a longer length of cable.  If the hub fails, nodes attached to it are disabled.  The cost of the hub makes the network expensive as compared to bus and ring topology. 38  Mesh Topology  In a mesh topology, every device has a dedicated point-to-point link to every other device.  a host is connected to one or multiple hosts. This topology has hosts in point-to-point connection with every other host or may also have hosts which are in point-to-point connection with few hosts only. 39 Advantages of Mesh Topology  The use of large number of links eliminates network congestion.  If one link becomes unusable, it does not disable the entire system. Disadvantages of Mesh Topology  The amount of required cabling is very large.  As every node is connected to the other, installation and reconfiguration is very difficult.  The amount of hardware required in this type of topology can make it expensive to implement 40  Hybrid Topology  A network structure whose design contains more than one topology is said to be hybrid topology.  Hybrid topology inherits merits and demerits of all the incorporating topologies. Mixture of two or more topologies. 41  PROTOCOLS A protocol is 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. The protocols can be broadly classified into three major categories: 1.Network Communication 2.Network Management 3.Network Security 42  Network Communication These protocols formally set out the rules and formats through which data is transferred. These protocols handle syntax, semantics, error detection, synchronization, and authentication. Some of them are 1. Hypertext Transfer Protocol(HTTP) It is a layer 7 protocol that is designed for transferring a hypertext between two or more systems. HTTP works on a client-server model, most of the data sharing over the web is done through using HTTP. 43 2.Transmission Control Protocol(TCP) It is a connection-oriented protocol i.e., it establishes a connection between applications before sending any data.  It is used for communicating over a network. It has many applications such as emails, FTP, streaming media, etc. 3. User Datagram Protocol(UDP) It is used when we want faster transmission, for multicasting and broadcasting connections, etc. It is a connectionless protocol 44  Network Management These protocols assist in describing the procedures and policies that are used in monitoring, maintaining, and managing the computer network. 1. Internet Control Message Protocol(ICMP) is used for reporting congestions, network errors, diagnostic purposes, and timeouts. 2. File Transfer Protocol(FTP): is a Client/server protocol that is used for moving files to or from a host computer, it allows users to download files, programs, web pages, and other things that are available on other services. 45  Network Security These protocols make sure that no unauthorized devices, users, or services can access the network data. Primarily, these protocols depend on encryption to secure data. 1. Secure Socket Layer(SSL) All the data transferred through SSL is encrypted thus stopping any unauthorized person from accessing it. It is a network security protocol mainly used for protecting sensitive data and securing internet connections 2. Transport Layer Security(TLS) It is generally used for encrypted communication between servers and web apps, like a web browser loading a website, it can also be used for encryption of messages, emails. 46  Network Line Configuration 1.A point-to-point connection  is the simplest form of network communication, where data can be sent and received exclusively between the two connected nodes.  Provides a dedicated link between two devices.  Is a protocol that provides a standard method for transporting multi-protocol datagrams over point to point links. Comprises three main components 1.A method for encapsulating multi-protocol datagrams 2.A link control protocol for establishing ,configuring, and testing the data-link connection. 3.A family of network control protocol for establishing and configuring different network layer protocols. 47  The point-to-point scheme provides separate communication channels for each pair of computers. When more than two computers need to communicate with one another, the number of connections grows very quickly as number of computer increases. Below figure illustrates that two computers need only one connection, three computers need three connections and four computers need six connections. 48 49 50 51