Unit II: Computer Networks Marks:10
●Evolution of networking: introduction to computer networks, evolution of networking (ARPANET, NSFNET, INTERNET) ● Data communication terminologies: concept of communication, components of data communication (sender, receiver, message, communication media, protocols), measuring capacity of communication media (bandwidth, data transfer rate), IP address, switching techniques (Circuit switching, Packet switching) ● Transmission media: Wired communication media (Twisted pair cable, Co-axial cable, Fiber-optic cable), Wireless media (Radio waves, Micro waves, Infrared waves) ● Network devices (Modem, Ethernet card, RJ45, Repeater, Hub, Switch, Router, Gateway, WIFI card) ● Network topologies and Network types: types of networks (PAN, LAN, MAN, WAN), networking topologies (Bus, Star, Tree) ● Network protocol: HTTP, FTP, PPP, SMTP, TCP/IP, POP3, HTTPS, TELNET, VoIP ● Introduction to web services: WWW, Hyper Text Markup Language (HTML), Extensible Markup Language (XML), domain names, URL, website, web browser, web servers, web hosting
Network : A network is an interconnected collection of autonomous computer that can share and exchange information./ Applications of networks: information sharing and exchange, peripheral resources sharing , software sharing, Access and share remote database , provide communication media/Advantage of networking (network goals): resource sharing , reliability ,reduce cost, fast communication Disadvantage:· Server faults stop applications from being available.· Network faults can cause loss of data./history or evolution of network :first network ARPANET((Advanced Research Project Agency Network) is a project sponsored by U. S. Department of Defense in 1969 to connect computers at different universities and U.S defense. Then NSFnet was developed by the National Science Foundation in 1980 which was high capacity network and strictly used for academic and engineering research. In 1990s the internetworking of ARPANET, NSFNET and other private network combined and named Internet/Internet: worldwide network of computer networks/ Protocol: Set of rules for communication over internet is called protocol./ Node: a computer attached to a network is called node /
Data Communication: is an act of sending or receiving data over network between two or more network devices/Components: sender, receiver, message, communication media, protocols )/ Data transfer rate (DTR): is the amount of digital data that's moved from one place to another in a given time. Data transfer rate is actually a measure of the speed at which network components can exchange data(send or receive). It is measured in either bits per second or bytes per second. / Bandwidth: A measure of the data transfer rate or capacity of a given network. Maximum data transfer rate of a network or Internet connection./ IP Address: Unique numeric address of each resource available on the internet is called IP address. It is written in dotted decimal form as 216.27.61.157. There are two type of IP address IPV4 and IPV6 / IPV4: 32 BIT long/Format: X.X.X.X Where X called octet and must be decimal value between 0 TO 255. IPV4 Has 4 octets./IPV6: 128 BIT long/Format: X:X:X:X:X:X:X:X Where X is called octet and must be hexadecimal value between 0 TO FFFF. IPV6 has 8 octets./ DNS: stands for domain name system :character based naming system by which servers are identified on internet .some most common domains are .com for commercial firms , .gov for government organizations, .edu for educational firms, .net for network resources ISPs/networks,org for non profit organizations like NGOs, .co for listed companes/In addition to it two letter abbreviation indicating country name like www.microsoft.co.in in stands for india, .au stands for Australia , .fr stands for france,.uk stands for united kingdom./
Switching techniques: Switching is the process of transferring data packets from one device to another in a network. Three switching methods are using during data transmission over network 1.circuit switching: A complete physical path is established between sender(source) computer and receiver(destination)computer on network before data transmission. It involves three phase’s connection establishment, data transfer and disconnection. A Telephone System uses this system to connect to subscribers for telephone conversation. 2. Message Switching: A message is a logical unit of information. Sender computer attach address of destination computer to the message and transmit it to its destination computer by store and forward or broadcast method. Mobile devices use this system for sending messages 3.Packet Switching: Similar to message switching but data are divided in fix size of packets and transmit independently over the network. Internet use packet switching .Advantage: packets are small and fix size and stored in main memory while in message switching complete message stored in disk. Transmission is fast because intermediate nodes do not have to wait for entire message.
Network devices: Components used to connect computers in a network Modem: hardware device that allow your computer to connect and communicate with other computers via analog telephone lines is called modem/. Modem converts digital signals into analog and vice versa This process in called modulation and demodulation. /RJ-45: Register jack-45,8 wired connector, used to connect computers in Ethernet LANs/Ethernet LAN is specially designed by Xerox Corp with DEC and Intel. Ethernet uses either a bus or star topology. /Hub: a Networking device to connect multiple computers together in LAN . Hub broadcast data. It share and distributes bandwidth with all connected computer. Two types : active hub and passive hub. Active hubs: amplify the signals before sending to another node / Passive hub pass the signal from on computer to another without any change. Hub broadcast the broadcast the message without any filtration/Switch: networking device to connect multiple computers in a LAN /It is smart than a hub because a switch will only send a message to the device that needs or request it, rather than broadcasting the same message to all its ports / Switch does not share bandwidth , rather each computer gets full bandwidth./ Bridge : A network device that connect two local networks with same protocols but with different types of cables. Bridge works on MAC address./Router : It is similar to bridge but can handle different protocols. Select the best path among multiple paths for data transfer on network./Repeater : network device that amplifies and restores signals for long distance transmission./ GateWay: network device that connects two dissimilar networks/NIC: Network adapter is a network card installed in your computer so that your computer can connect with internet. A NIC is also known as a network interface controller (NIC), network interface controller card, expansion card, computer circuit board, network card, LAN card, network adapter or network adapter card (NAC).NIC manufacturer assigns a unique physical address to each NIC card. This address called MAC Address. It is 6 byte address with each byte separated by a colon 10:85:03:63:2E:FC where first three bytes are manufacturer ID and last three represent card no/Wi-Fi: Wi-Fi stands wireless fidelity. Commonly used, for connecting devices in wireless mode. /
Wireless or unguided media(Devices connected through electromagnetic waves): 1. Microwaves(Line of sight transmission): transmit signal such as mobile phone calls 2,Radio waves: (Omni directional )Used to transmit radio and TV signals. Transmit information (audio , video and text), Wi-Fi also use Radio waves
/3. Satellite Microwaves: The satellites accept data/signals transmitted from an earth station, amplify them, and retransmit them to another earth station(DTH,VSAT)/4.Infrared waves: (communicate device within short range) remote control, blue tooth devices / Twisted pair Cable: Two thin copper wires are twisted around each other to reduce cross talk. These type of cables are commonly used in local telephone communication and short distance digital communication. Two types UTP(Unshielded Twisted Pair ) Cable and STP(shielded twisted pair) Cable/UTP has 7 groups CAT 1 to CAT 6/ Advantage : simple and easy to install and maintain, low weight ,low cost /Disadvantage : high attenuation(signal became weak on long distance ,low bandwidth capability / 2. Coaxial cable: consist of a solid copper wire a PVC insulation over which there is a sleeve of copper mesh. This is widely used for television signals. In form of CABLE TV cable, it provides a cheap mans of transporting multi-channel television signals around metropolitan areas. Advantage : Higher bandwidth can be used for broadband transmission, Disadvantage : expensive. Two types: Thicknet and Thinnet. Thicknet: thicker then thinnet max segment size upto 500 meters long. Thinnet: max segment size 185meters/ 3.Optical fibers: It is made of glass or plastic and transmits signals in the form of light. The light source used are light emitting diodes (LEDs) or laser Diodes(LDs). It can be used for broadband transmission. Advantage : higher bandwidth, light weight, secure transmission . Disadvantage : installation and maintenance , high cost, unidirectional light propagation
Network Topology: The physical arrangement of nodes in a network is called network topology. The factors to select a topology are cost, flexibility and reliability/Star topology :a central node to which all other nodes are directly connected via single path. Adv: ease of service, one device per connection, simple access protocol. Disadv: long cable length, central node dependency, difficult to extend/Bus or linear :It consist of A single length coaxial cable onto which various nodes are directly connected. data can be transmitted in both direction and data is broadcasted to all nodes. data is transmitted in form of packets. Adv: short cable length, easy to extend. Disadv: fault diagnosis is difficult, fault isolation is difficult, repeater configuration /Ring or circular topology: nodes are connected in ring form. Each node is connected only its two neighbor nodes. Adv: short cable length, no wiring closet space required, suitable for optical fibers. Disadv: Difficult to diagnose faults, network reconfiguration ts difficult, node failure causes network failure/Graph topology : nodes are connected in arbitrary fashion. A node may or not may connected two or more nodes. It is not necessary that all the nodes are connected. Tree topology: nodes are connected in network in shape of inverted tree. Fully connected topology: each node in directly connected to another node in network./Mesh Topology: Each node is connected to more than one node to provide an alternative route in the case the host is either down or too busy. This is excellent for long distance networking/ Types of network : PAN(personal area network),LAN(local area network),MAN(Metropolitan area network )and WAN(Wide area network)/PAN(different digital devices are connected on a single location or at home )LAN( up to 10 km) (spread in few kilometers, span in small area such as building, group of buildings ,a university campus, complete ownership by single organization, very less error rates, high data rate in multiple mbps)/MAN(up to 10 km ) (spread over a city for example cable TV Network)/WAN(More than 100 km ) (spread across countries, it can be a group of LANs spread across several locations, high error rates, low data rates less than 1Mbps,Owned by multiple organization, Internet is an example of WAN)/ Based on the role played by the network computers in the network operation , network can classified in two types : 1.Peer to Peer network: On small network , a workstation that can double up as a server. Computers are called non dedicated computers. All computers are equal. Each can play role of client as well as sever. There is no control over security. It is slower and require more memory. There is no central control over the network. Clients are not depend on central sever. 2. Client Server Network(Master-slave networks):On bigger network installation, there is a computer reserved for the server’s job. Its only job to help other computers (clients) to access data, software and hardware resources. Such server is called dedicated server. A client computer is a computer on network that request for services to server. A sever is a computer on network, dedicated to processing client requests./ Server is placed where maximum number of computers exist. It reduce network traffic /Hub or switch will be required in all blocks to form LAN/Radio wave transmission is the most economical way to connect with a reasonable high speed in hilly region where cable connection in not feasible/Very fast and effective wired internet connection in optical fiber cable//Firewall is used to save private company network from internet/ layout or structure may be bus/star/ring/Mesh as given distance/ type of wired internet connection : 1. Dial up(Slowest) 2. Broadband 3.Fiber optical (leased line connection)/Difference between HTML and XML: HTML displays data and describes the structure of a webpage, whereas XML stores and transfers data. XML is a standard language which can define other computer languages, but HTML is a predefined language with its own implications. HTML has predefine tags but in xml we can design custom tags/ Expand the terms:FTP: File transfer protocol / SFTP: Secure File transfer protocol/IOT: Internet of things /VOIP: voice over internet protocol SCP: Secure Copy Protocol/SSL: Secure Socket Layer/Telnet: teletype network(remote login program): software used to access remote computer//SMTP: Simple Mail transfer protocol/POP: Post Office protocol/HTTP:Hyper text transfer protocol/TLS: Transport Layer Security/Wi-Fi: wireless fidelity/NIC: An NIC (network interface card)/DNS: Domain Name System/GPS: Global Positioning System/DTH: Direct to Home/DHCP: Dynamic host configuration protocol/CDMA: Code division Multiple Access/SSH: Secure Shell or Secure Socket Shell(remote login program)/HTTPS:Hyper text transfer protocol Secure//W3C: World Wide Consortium/IP : Internet Protocol/IPv6: Internet Protocol Version 6/IPv4: Internet Protocol Version 4/TCP: Transmission Control Protocol/UDP: User Datagram Protocol/NIU: Network interface Unit/STP: Shielded Twisted Pair/UTP: Unshielded Twisted Pair/RJ-45 : Registered jack connector//
TCP/IP : It is a set of rules (protocols) govern communication among all computers over the internet .It specify how data is exchanged over the internet /It identify how it should be broken into packets, addressed, transmitted, routed and received at the destination. TCP: is responsible for the data delivery of packets and IP: is responsible for the logical addressing. IP obtain the address and TCP guarantees delivery of data to that address. /HTTPS stands for Hyper Text Transfer Protocol Secure. It is a protocol for securing the communication between two systems e.g. the browser and the web server./HTTPS established an encrypted link between the browser and the web server
URL: Uniform Resource Locator/XML: Extensible Markup language/VoIP:Voice over Internet Protocol (VoIP), is a technology that allows you to make voice calls using Internet connection instead of a regular (or analog) phone line. /Simple Mail Transfer Protocol (SMTP) is an Internet protocol for sending e-mail across the internet/ POP3 (Post Office Protocol 3) Protocol used for receiving emails from a remote server to a local email client. POP3 is a client/server protocol in which e-mail is received and held for you by your Internet server. IMAP(Internet message Access Protocol) : is also e-mail receiving protocol. / The File Transfer Protocol (FTP) is a standard network protocol used to transfer computer files between a client and server on a computer network./
Remote Login: It is a network application that allows a user to work on remote computer. The access in granted only after valid login id and password. There are TELNET and SSH are two remote login programs/Web browser: software used to explore or run web pages or web sites .They are used to make request for web pages. for example internet explorer, Mozilla, Firefox, opera, Google chrome etc./web server(web host): Software that respond to the request made by the web clients. Web server actually a collection of web sites. For example tomcat, web-logic, IIS server etc/Web hosting :(store and maintain websites on a server ) hosting(placing) a web server software on a computer system and allow customers to place their web sites on this host computer. These websites always available for web clients via internet/WWW: stands for World Wide Web. It is a set of protocols that allows us to access web page on net through a URL.WWW is a small part of internet. www supports various attributes like user-friendly, multimedia documents, hypertext and hyperlinks, interactive, frames /
Web site: collection of web pages. placed on a web server/web portal: a website which host other websites. A web portal has hyperlinks to many other web sites/Home page: first page of a web site it open when we open the website/download : transfer files from server to local computer/upload : transfer file from local computer to server computer/The most suitable place to host server would be the block ( ) as this block contain maximum number of computers. It decreases the cabling cost and increasing the efficiency of the maximum no of computers in the network. It also makes most of the traffic local, which is as required by 80-20 network design rule.
80-20 rule of network design: 80% traffic on a given network segment should be local and not more than 20% of the network traffic should need to move across backbone. Therefore server is placed where large no of computer placed./Because the distance between given block is more than 70 m so repeater is needed to avoid loss of signals
It regenerate data and voice signals /Hub/Switch each would be needed in all the blocks to form LAN /Modem is placed for internet connectivity where server is available. /
Wireless connectivity in hilly area : radio wave transmission because radio waves are Omni directional so that transmitter and receiver do not have to be carefully aligned physically / Fastest Wired connectivity in plain area: Optical Fiber/ low speed cheap wired connection : broadband connection/
Difference between: HTTP and HTTPS / IPV-4 and IPV-6 / HTML AND XML/Switch And Hub /Web Browser And Web Server/ Bus And Star Topology/Packet And Circuit Switching/Advantage And Disadvantages Of Star/Bus Topology/ URL and DOMAIN NAME(DNS)/HTTP and FTP
Explain the terms: 1. TCP/IP 2. WEB HOSTING 3. WEB SERVER 4. WEB BROWSER 5. CIRCUIT SWITCHING 6. PROTOCOL 7.FTP 8. modem 9. HUB 10.Firewall 11. HTML 12. WWW 13. Telnet 14.DNS 15.URL 16. IP Address
5 marks question ? 1. Where server will be placed and why 2. Where modem will be placed? 3. Where hub/switch will be placed? 4. What will be layout of network? 5. Where repeater should be placed? 6. What is the type of Network in given network? 7. Which type of internet connectivity can be used ?
MAC Address (Physical address, 6 byte address, Fixed Address, Represented by hexadecimal number)
IP Address (Logical address, 4 and 6 byte, may change, Represented in decimal format)
URL (Uniform Resource Locator, complete address to a specific webpage on the internet , e.g https://www.w3schools.com/whatis/whatis_html.asp )
DNS(Domain Name System, Part of URL,. Google.com , www.w3schools.com )
HTTP(Transfer web pages between a client and a server ,authentication not required, transfer small files or data, stateless protocol )
FTP: (FTP is used to transmit files among different hosts. , requires authentication to transfer files from one host to another, Used to transfer large files, FTP can maintain states)
Web Server(Serve or response for web request, Used to store websites, E.g Tomcat, IIS, Web-logic)
Web Browser(request for web page, Used to access the web sites, e.g Google chrome, firefox, opera mini etc)
Circuit switch(Physical path established before data transfer between sender and receiver, Reserver entire bandwidth, All packets use same path)
Packet Switch( no Physical path, Dose not reserve, all packets move independently )
HTML( display and design data, predefined tags, case insensitive ,static)
XML( store and transport data, custom tags, case sensitive, dynamic)