UNIT 1 Net & Int. PDF

1 Networking, Internet & Web Page Development Unit-1 Introduction to Computer Network Prepare by: Bagha Rizwan A. → Basics of Computers → Computer Network → Type of Computer N...

1 Networking, Internet & Web Page Development Unit-1 Introduction to Computer Network Prepare by: Bagha Rizwan A. → Basics of Computers → Computer Network → Type of Computer Network → Network Topology → OSI Reference Model (Introduction) → TCP/IP → Internet Terminology → ISP (Internet Service Provider) → Intranet → VSAT (very small aperture terminal)URL Prepared By: Bagha Rizwan A. 2 Networking, Internet & Web Page Development Introduction to Computer Network A computer network is a group of devices connected with each other through a transmission medium such as wires, cables etc. These devices can be computers, printers, scanners, Fax machines etc. The purpose of having computer network is to send and receive data stored in other devices over the network. These devices are of often referred as nodes. A computer network is a group of two or more interconnected computer systems. You can establish a network connection using either cable or wireless media. Advantages of a Computer Network Here are the fundamental benefits/pros of us using Computer Networking: Helps you to connect with multiple computers together to send and receive information when accessing the network. Helps you to share printers, scanners, and email. Helps you to share information at very fast speed Electronic communication ication is more efficient and less expensive than without the network. There are five basic components of a computer network Message:: It is the data or information which needs to be transferred from one device to another device over a computer network. Sender:: Sender is the device that has the data and needs to send the data to other device connected to the network. Prepared By: Bagha Rizwan A. 3 Networking, Internet & Web Page Development Receiver: A receiver is the device which is expecting the data from other device on the network. Transmission media: In order to transfer data from one device to another device we need a transmission media such as wires, cables, radio waves etc. Protocol: A protocol is a set of rules that are agreed by both sender and receiver, without a protocol two devices can be connected to each other but they cannot communicate. In order to establish a reliable communication or data sharing between two different devices we need set of rules that are called protocol. Switches Switches work as a controller which connects computers, printers, and other hardware devices to a network in a campus or a building. Routers Routers help you to connect with multiple networks. It enables you to share a single internet connection with multiple devices and saves money. This networking component acts as a dispatcher, which allows you to analyze data sent across a network. It automatically selects the best route for data to travel and send it on its way. Servers: Servers are computers that hold shared programs, files, and the network operating system. Servers allow access to network resources to all the users of the network. Transmission Media: Transmission media is a carrier used to interconnect computers in a network, such as coaxial cable, twisted-pair wire, and optical fiber cable. It is also known as links, channels, or lines. Access points Access points allow devices to connect to the wireless network without cables. A wireless network allows you to bring new devices and provides flexible support to mobile users. Shared Data: Prepared By: Bagha Rizwan A. 4 Networking, Internet & Web Page Development Shared data are data which is shared between the clients such as data files, printer access programs, and email. Network Interface Card: Network Interface card sends, receives data, and controls data flow between the computer and the network. Local Operating System: A local OS which helps personal computers to access files, print to a local printer and uses one or more disk and CD drives which are located on the computer. Network Operating System: The network operating system is a program which runs on computers and servers. It allows the computers to communicate via network. Hub: Hub is a device that splits network connection into multiple computers. It acts a distribution center so whenever a computer requests any information from a computer or from the network it sends the request to the hub through a cable. The hub will receive the request and transmit it to the entire network. LAN Cable: Local Area Network(LAN) cable is also called as Ethernet or data cable. It is used for connecting a device to the internet. OSI: OSI stands for Open Systems Interconnection. It is a reference model which allows you to specify standards for communications. Prepared By: Bagha Rizwan A. 5 Networking, Internet & Web Page Development Features of a Computer Network A computer network has following features: Performance:: Performance of a computer network is measured in terms of response time. The response time of sending and receiving data from one node (computer in a computer network are often referred as node) to another should be minimal. Data Sharing:: One of the reason why we use a computer network is to share the data between etween different systems connected with each other through a transmission media. Backup:: A computer network must have a central server that keeps the backup of all the data that is to be shared over a network so that in case of a failure it should be able to recover the data faster. Reliability:: There should not be any failure in the network or if it occurs the recovery from a failure should be fast. Security:: A computer network should be secure so that the data transmitting over a network should be safe from unauthorized access. Also, the sent data should be received as it is at the receiving node, which means there should not be any loss of data during transmission. Prepared By: Bagha Rizwan A. 6 Networking, Internet & Web Page Development Scalability:: A computer network should be scalable which means it should always allow to t add new computers (or nodes) to the already existing computer network. For example, a company runs 100 computers over a computer network for their 100 employees, lets say they hire another 100 employees and want to add new 100 computers to the already existing isting LAN then in that case the local area computer network should allow this. Software and hardware compatibility compatibility:: A computer network must not limit all the computers in a computer network to use same software and hardware, instead it should allow the better compatibility between the different software and hardware configuration. Computer Network Architecture A Computer Architecture is a design in which all computers in a computer network are organized. A architecture defines how the computers should get connected to get the maximum advantages of a computer network such as better response time, security, scalability etc. The two most popular computer architectures are P2P (Peer to Peer) and Client-Server Server architecture architecture. Peer to Peer Architecture In peer to peer architecture all the computers in a computer network are connected with every computer in the network. Every computer in the network use the same resources as other computers. There is no central computer that acts as a server rather all computers compu acts as a server for the data that is stored in them. Prepared By: Bagha Rizwan A. 7 Networking, Internet & Web Page Development Advantages of a Peer to Peer Architecture 1. Less costly as there is no central server that has to take the backup. 2. In case of a computer failure all other computers in the network are not affected and they will continue to work as same as before the failure. 3. Installation of peer to peer architecture is quite easy as each computer manages itself. Disadvantages of a Peer to Peer Architecture 1. Each computer has to take the backup rather than a central computer and the security measures are to be taken by all the computers separately. 2. Scalability is a issue in a peer to Peer Architecture as connecting each computer to every computer is a headache on a very large network. Client Server Architecture In Client Server architecture a central computer acts as a hub and serves all the requests from client computers. All the shared data is stored in the server computer which is shared with the client computer when a request is made by the client computer. All the communication takes place through the server computer, for example if a client computer wants to share the data with other client computer then it has to send the data to server first and then the server will send the data to other client. Prepared By: Bagha Rizwan A. 8 Networking, Internet & Web Page Development Advantages of Client Server Architecture 1. Data backup is easy and cost effective as there is no need to manage the backup on each computer. 2. Performance is better as the response time is greatly improves because the server is more powerful computer than the other computers in the network. 3. Security is better as unauthorized access are denied by server computer and all the data goes through the server. 4. Scalability is not an issue in this Architecture as large number of computers can be connected with server. Disadvantages of Client Server Architecture 1. In case of server failure entire network is down. 2. Server maintenance cost is high as the server is the main component in this Architecture 3. Cost is high as the server needs more resources to handle that many client requests and to be able to hold large amount of data. Network Topologies A Network Topology is the arrangement with which computer systems or network devices are connected to each other. Topologies may define both physical and logical aspect of the network. Both logical and physical topologies could be same or different in a same network. Point-to-Point Point-to-point point networks contains exactly two hosts such as computer, switches or routers, servers connected back too back using a single piece of cable. Often, the receiving end of one host is connected to sending end of the other other. If the hosts are connected point point-to-point point logically, then may have multiple intermediate devices. But the end hosts are unaware of underl underlying ying network and see each other as if they are connected directly. Prepared By: Bagha Rizwan A. 9 Networking, Internet & Web Page Development Bus Topology In case of Bus topology, all devices share single communication line or cable. Bus topology may have problem while multiple hosts sending data at the same time. Therefore, Bus topology either uses CSMA/CD technology or recognizes one host as Bus Master to solve the issue. It is one of the simple forms of networking where a failure of a device does not affect the other devices. But failure of the shared communication line can ma make ke all other devices stop functioning. Both ends of the shared channel have line terminator. The data is sent in only one direction and as soon as it reaches the extreme end, the terminator removes the data from the line. Star Topology All hosts in Star topology are connected to a central device, known as hub device, using a point-to-point 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 1 device such as hub or repeater Layer-2 2 device such as switch or bridge Layer-3 3 device such as router or gateway Prepared By: Bagha Rizwan A. 10 Networking, Internet & Web Page Development As in Bus topology, hub acts as single point of failure. If hub fails, connectivity of all hosts to all other hosts fails. Every communication between hosts, takes place through only the hub.Star topology is not expensive as to connect one more host, only one cable is required and configuration is simple. Ring Topology In ring topology, 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. To connect one more host in the existing structure, the administrator may need only one more extra cable. Failure of any host results in failure of the whole ring. Thus,, every connection in the ring is a point of failure. There are methods which employ one more backup ring. Mesh Topology In this type of topology, a host is connected to one or multiple hosts. This topology has hosts in point-to-point point connection with every other host or may also have hosts which are in point-to-point point connection to few hosts only. Prepared By: Bagha Rizwan A. 11 Networking, Internet & Web Page Development Hosts in Mesh topology also work as relay for other hosts which do not have direct point-to- point point oint links. Mesh technology comes into two types: Full Mesh:: All hosts have a point point-to-point point connection to every other host in the network. Thus for every new host n(n n(n-1)/2 1)/2 connections are required. It provides the most reliable network structure among all network topologies. Partially Mesh:: Not all hosts have point point-to-point point connection to every other host. Hosts connect to each other in some arbitrarily fashion. This topology exists where we need to provide reliability to some hosts out of all. Tree Topology Also known as Hierarchical Topology, this is the most common form of network topology in use presently.This topology imitates as extended Star topology and inherits properties of bus topology. This topology divides the network in to multiple levels/layer levels/layers s of network. Mainly in LANs, a network is bifurcated into three types of network devices. The lowermost is access-layer access where computers are attached. The middle layer is known as distribution layer, which works as mediator between upper layer and lower la layer. yer. The highest layer is known as core layer, and is central point of the network, i.e. root of the tree from which all nodes fork. 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. Prepared By: Bagha Rizwan A. 12 Networking, Internet & Web Page Development The above picture represents an arbitrarily hybrid topology. The combining topologies may contain attributes of Star, Ring, Bus, and Daisy Daisy-chain chain topologies. Most WANs are connected connecte by means of Dual-Ring Ring topology and networks connected to them are mostly Star topology networks. Internet is the best example of largest Hybrid topology OSI Model Open System Interconnect is an open standard for all communication systems. OSI model is established stablished by International Standard Organization (ISO). This model has seven layers: Prepared By: Bagha Rizwan A. 13 Networking, Internet & Web Page Development Application Layer:: This layer is responsible for providing interface to the application user. This layer encompasses protocols which directly interact with the user. Presentation Layer:: This layer defines how data in the native format of remote host should be presented in the native format of host. Session Layer:: This layer maintains sessions between remote hosts. For example, once user/password authentication is done, the remote host maintains this session for a while and does not ask for authentication again in that time span. Transport Layer:: This layer is responsible for end end-to-end end delivery between hosts. Network Layer:: This layer is responsible for address assignme assignment nt and uniquely addressing hosts in a network. Data Link Layer:: This layer is responsible for reading and writing data from and onto the line. Link errors are detected at this layer. Physical Layer:: This layer defines the hardware, cabling wiring, power output, ou pulse rate etc What is TCP/IP model? The TCP model stands for Transmission Control Protocol, whereas IP stands for Internet Protocol.. A number of protocols that make the internet possibly comes under the TCP/IP model. Nowadays, we do not hear the na name me of the TCP/IP model much, we generally hear the name of the IPv4 or IPv6, but it is still valid. This model consists of 4 layers. Now, we will look at the diagrammatic representation of the TCP/IP model. This model has the following layers: Prepared By: Bagha Rizwan A. 14 Networking, Internet & Web Page Development Application Layer: This layer defines the protocol which enables user to interact with the network. For example, FTP, HTTP etc. Transport Layer: This layer defines how data should flow between hosts. Major protocol at this layer is Transmission Control Protocol (TCP). This layer ensures data delivered between hosts is in-order and is responsible for end-to-end delivery. Internet Layer: Internet Protocol (IP) works on this layer. This layer facilitates host addressing and recognition. This layer defines routing. Link Layer: This layer provides mechanism of sending and receiving actual data. Unlike its OSI Model counterpart, this layer is independent of underlying network architecture and hardware. OSI Model TCP/IP Model It stands for Open System It stands for Transmission Control Protocol. Interconnection. OSI model has been developed by ISO It was developed by ARPANET (Advanced Research (International Standard Organization). Project Agency Network). It is an independent standard and It consists of standard protocols that lead to the generic protocol used as a development of an internet. It is a communication communication gateway between the protocol that provides the connection among the network and the end user. hosts. In the OSI model, the transport layer The transport layer does not provide the surety for provides a guarantee for the delivery of the delivery of packets. But still, we can say that it is the packets. a reliable model. This model is based on a vertical This model is based on a horizontal approach. approach. In this model, the session and In this model, the session and presentation layer are presentation layers are separated, i.e., not different layers. Both layers are included in the both the layers are different. application layer. It is also known as a reference model It is an implemented model of an OSI model. through which various networks are built. For example, the TCP/IP model is built from the OSI model. It is also referred to as a guidance tool. Prepared By: Bagha Rizwan A. 15 Networking, Internet & Web Page Development In this model, the network layer The network layer provides only connectionless provides both connection-oriented and service. connectionless service. Protocols in the OSI model are hidden In this model, the protocol cannot be easily replaced. and can be easily replaced when the technology changes. It consists of 7 layers. It consists of 4 layers. OSI model defines the services, In the TCP/IP model, services, protocols, and protocols, and interfaces as well as interfaces are not properly separated. It is protocol provides a proper distinction between dependent. them. It is protocol independent. The usage of this model is very low. This model is highly used. It provides standardization to the It does not provide the standardization to the devices like router, motherboard, devices. It provides a connection between various switches, and other hardware devices. computers. Prepared By: Bagha Rizwan A. 16 Networking, Internet & Web Page Development Internet Service Providers (ISP) Internet Service Provider (ISP) is a company offering access to internet. They offer various services: Internet Access Domain name registration stration Dial-up access Leased line access ISP Types ISPs can broadly be classified into six categories as shown in the following diagram: Access providers They provide access to internet through telephone lines, cable wi wi-fi fi or fiber optics. Mailbox Provider Such providers offer mailbox hosting services. Hosting ISPs Hosting ISPs offers e-mail, and other web hosting services such as virtual machines, clouds etc. Virtual ISPs Such ISPs offer internet access via other ISP services. Free ISPs Free ISPs do not charge for internet services. Prepared By: Bagha Rizwan A. 17 Networking, Internet & Web Page Development Intranet Intranet is defined as private network of computers within an or organization ganization with its own server and firewall. Moreover we can define Intranet as: Intranet is system in which multiple PCs are networked to be connected to each other. PCs in intranet are not available to the world outside of the intranet. Usually each company any or organization has their own Intranet network and members/employees of that company can access the computers in their intranet. Every computer in internet is identified by a unique IP address. Each computer in Intranet is also identified by a IP Addre Address, ss, which is unique among the computers in that Intranet. Benefits Intranet is very efficient and reliable network system for any organization. It is beneficial in every aspect such as collaboration, cost cost-effectiveness, effectiveness, security, productivity and much more. Prepared By: Bagha Rizwan A. 18 Networking, Internet & Web Page Development Communication Intranet offers easy and cheap communication within an organization. Employees can communicate using chat, e-mail or blogs. Time Saving Information on Intranet is shared in real time. Collaboration Information is distributed among the employees as according to requirement and it can be accessed by the authorized users, resulting in enhanced teamwork. Platform Independency Intranet can connect computers and other devices with different architecture. Cost Effective Employees can see the data and other documents using browser rather than printing them and distributing duplicate copies among the employees, which certainly decreases the cost. Workforce Productivity Data is available at every time and can be accessed using company workstation. This helps the employees work faster. Prepared By: Bagha Rizwan A. 19 Networking, Internet & Web Page Development Business Management It is also possible to deploy applications that support business operations. Security Since information shared on intranet can only be accessed within an organization, therefore there is almost no chance of being theft. Specific Users Intranet targets only specific users within an organization therefore, once can exactly know whom he is interacting. Immediate Updates Any changes made to information are reflected immediately to all the users. Difference Between Internet and Intranet Internet Intranet The Internet is a wide network of Intranet is a network of computers designed for a computers and is available to all. certain group of users. Internet contains a large number of Intranet can be accessed from the Internet with intranets. specific restrictions. Number of internet users is very high. Number of users is limited. Internet contains various source of Intranet only contains group-specific information. information. Anyone can access the internet Accessible only by the organization employees or admin who have login details. It is not as safe as compared to intranet Safe and secure network. It is a public network. It is a private network. Prepared By: Bagha Rizwan A. 20 Networking, Internet & Web Page Development Very Small Aperture Terminal (VSAT) VSATs (Very Small Aperture Terminals) is a two way, lost cost, ground micro station for transmitting data to and from communication satellites. A VSAT has a dish antenna with diameters between 75 cm to 1 m, which is very small in comparison with 10 m diameter of a standard GEO antenna. It accesses satellites in geosynchronous orbits or geostationary orbits. Data rates in VSATs ranges from 4 Kbps to 16 Mbps. Communication systems increasingly offer the possibility to communicate to somebody anywhere and anytime. In telephony, this becomes evident by the development of cellular telephone networks. have access to low-Earth-orbit (LEO) satellites. Configurations of VSATs Star Topology − This has a central uplink site which transmits data from and to each VSAT through the satellite. Mesh Topology − Each VSAT transmits data via the satellite to the other stations. The above diagram shows mesh topology of VSATs. Combination of the above Disadvantages The disadvantages of VSAT are as follows− Latency − VSAT technology uses satellites in geosynchronous orbit. It takes a minimum latency of 500 milli sec. Poor choice for online gaming. Installation − It requires an outdoor antenna. This makes installation a big problem. Prepared By: Bagha Rizwan A. 21 Networking, Internet & Web Page Development Types of Networks 1. Personal Area Network PAN is the acronym for Personal Area Network. PAN is the interconnection between devices within the range of a person’s private space, typically within a range of 10 meters. If you have transferred images or songs from your laptop to mobile or from mobile to your friend’s mobile using Bluetooth, you have set up and used a personal area network. 2. Local Area Network LAN or Local Area Network is a wired network spread over a single site like an office, building or manufacturing unit. LAN is set up to when team members need to share software and hardware resources with each other but not with the outside world. Typical software resources include official documents, user manuals, employee handbook, etc. Hardware resources that can be easily shared over the network include printer, fax machines, modems, memory space, etc. This decreases infrastructure costs for the th organization drastically. Prepared By: Bagha Rizwan A. 22 Networking, Internet & Web Page Development 3. Metropolitan Area Network MAN is the acronym for Metropolitan Area Network. It is a network spread over a city, college campus or a small region. MAN is larger than a LAN and typically spread over several kilometers.. Objective of MAN is to share hardware and software resources, thereby the decreasing infrastructure costs. MAN can be built by connecting several LANs. 4. Wide Area Network WAN or Wide Area Network is spread over a country or many countries. WAN is typically a network of many LANs, MANs and WANs. Network is set up using wired or wireless connections, ections, depending on availability and reliability. Prepared By: Bagha Rizwan A. 23 Networking, Internet & Web Page Development Best of Luck Prepared By: Bagha Rizwan A.