Computer Networks and Cloud Computing Unit 1 Notes PDF

UNIT I INTRODUCTION TO COMPUTER NETWORKS 1.1 USES OF COMPUTER NETWORKS | Computer Network provides sever...

UNIT I INTRODUCTION TO COMPUTER NETWORKS 1.1 USES OF COMPUTER NETWORKS | Computer Network provides several uses, both to organizations and individual users. i 5 Resource Sharing This is the main purpose of a computer network. It defines creating all programs, peripherals and data feasible to anyone computer on the network to all other computers without considering the physical areas. Thus a user at a considerable distance can share the resources or see computer data in a similar Laser printer way that a local customer uses them. Another method of resource sharing is load sharing. If a job is needed, it can be implemented using various computers in a network by ‘ partitioning it, which reduces time consumption | - and loads both things for a particular computer. Fig. 1.1 Simultaneous Access computer network allows few users to create programs and data at the equivalent time. An example is a company's quarterly sales document, which several managers need to view and update. We can store the information on a network server, which is a central computer with a huge storage device and other resources that all users can share. If the server stores files for users to The hard disk in this server is a shared storage device, which in the network’s access, it is generally known as a file users can access server. We can save an individual copy of a data file on the server, accessible to each employee in the organizations, as display in the Fig. 1.2. r -I r r Moreover, if one user changes the file, — = = other users will see the difference when AT Gananaaas Odaaazianas O using it. High Reliability due to Alternative Sources of Records Reliability is the main benefit due to which networks are becoming very popular among organizations. By using systems, critical data can be saved at more than one locations. If a computer fails or crashes, the data can be recovered from the network’s other computers. This way, the data is secured in a network. Cost Reduction The next phase of the computer network is the reduction of cost. Resources sharing automatically reduces cost, and hence money can be saved. One of the other aspects is that the prices of small computers are significantly less compared to mainframes. Though mainframes are roughly ten times compared to microcomputers, the cost to performance ratio is much better for small/microcomputers than large/mainframe computers. (1.1) COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.2) INTRODUCTION TO COMPUTER NETWORKS 5. Provide Communication Medium e A computer network offers a dynamic communication medium between extensively distinct people. It is easy for two or more person living far apart to work on the same project by partitioning it using a network. e Uses of Computer Network for People e The computer networks provide the following services to a person - > Access to Remote Information > Access to remote information comes in several forms. For example, ¢ Home shopping, paying telephone bills, e-banking, online share market, etc. e Itis possible to access an information system like the World Wide Web, which includes data about the craft, business, cooking, government, health, history, recreation, science, sports, etc. ¢ Newspaper is currently available online. You can access the news according to your interest. > Person-to-Person Communication > Person to person communication involves the following 6. Electronic-mail (E-mail) Sending and receiving email over a typical network is shown in the Fig. 1.3. MEMO To : Chetan Meeting Friday, 9:00 see you there, SG The sender composes an email mail message and sends it. @ The message is stored on the @ server. The server alerts the recipient that there is a message. When the recipient is ready to read the message, the recipient’'s computer retrieves it from the server. Fig. 1.3 Teleconferencing and Video Conferencing A teleconference is a virtual conference in which various people in multiple areas conduct discussions by typing messages. All the other people can see each message in the teleconference. If clients have the required hardware and software, they can view and talk to each other as they face online instead of merely typing messages. This process is known as videoconferencing. Worldwide Newsgroups Worldwide newsgroups in which one individual posts information and few other subscribers can interpret it or provide feedback. 9. Interactive Entertainment Interactive entertainment includes the following - Video on Demand : It is feasible to choose any movie and displayed it on your screen. Game Playing : You can enjoy multiperson real-time simulation games. It can participate in live TV programmes like quiz, contest, discussion, etc. COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.3) INTRODUCTION TO COMPUTER NETWORKS |1.2 TYPES OF COMPUTER NETWORKS | e A computer network is a group of computers linked to each other that enables the computer to communicate with another computer and share their resources, data, and applications. e A computer network can be categorized by their size. [Types of Computer] A computer network is mainly of four types: network 1. LAN (Local Area Network) v 2. PAN (Personal Area Network) 4 ‘ ‘ ‘ 3. MAN (Metropolitan Area Network) LA el R Sn 4. WAN (Wide Area Network) Fig. 1.4 1.2.1 LAN (Local Area Network) e Local Area Network is a group of computers connected to each other in a small area such as building, office. e LAN is used for connecting two or more personal computers through a communication medium such as twisted pair, coaxial cable, etc. e Itis less costly as it is built with inexpensive hardware such as hubs, network adapters, and ethernet cables. e The data is transferred at an extremely faster rate in Local Area Network. Local Area Network provides higher security. 1.2.2 PAN (Personal Area Network) Personal Area Network is a network arranged within an individual person, typically within a range of 10 meters. e Personal Area Network is used for connecting the 9 computer devices of personal use is known as Personal Area Network. \ / e Thomas Zimmerman was the first research scientist to %/ D bring the idea of the Personal Area Network. e e Personal Area Network covers an area of 30 feet. / e Personal computer devices that are used to develop the & |E U personal area network are the laptop, mobile phones, media player and play stations. Fig. 1.6 There are two types of Personal Area Network: Types of personal area network.. Wired personal Wireless personal area network area network Fig. 1.7 (i) Wired Personal Area Network (i) Wireless Personal Area Network COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.4) INTRODUCTION TO COMPUTER NETWORKS (i) Wireless Personal Area Network :Wireless Personal Area Network is developed by simply using wireless technologies such as WiFi, Bluetooth. It is a low range network. (ii) Wired Personal Area Network : Wired Personal Area Network is created by using the USB. Examples of Personal Area Network : e Body Area Network : Body Area Network is a network that moves with a person. For example, a mobile network moves with a person. Suppose a person establishes a network connection and then creates a connection with another device to share the information. e Offline Network: An offline network can be created inside the home, so it is also known as a home network. A home network is designed to integrate the devices such as printers, computer, television but they are not connected to the internet. ¢ Small Home Office: It is used to connect a variety of devices to the internet and to a corporate network using a VPN 1.2.3 MAN (Metropolitan Area Network) e A metropolitan area network is a network that covers a larger geographic area by interconnecting a different LAN to form a larger network. e Government agencies use MAN to connect to the citizens and private industries. ¢ In MAN, various LANs are connected to each other through a telephone exchange line. e The most widely used protocols in MAN are RS-232, Frame Relay, ATM, ISDN, OC-3, ADSL, etc. e It has a higher range than Local Area Network(LAN). Fig. 1.8 Uses of Metropolitan Area Network: e MAN is used in communication between the banks in a city. It can be used in an Airline Reservation. e [t can be used in a college within a city. It can also be used for communication in the military. 1.2.4 WAN (Wide Area Network) e A Wide Area Network is a network that extends over a large geographical area such as states or countries. e A Wide Area Network is quite bigger network than the LAN. e A Wide Area Network is not limited to a single location, but it spans over a large geographical area through a telephone line, fibre optic cable or satellite links. COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.5) INTRODUCTION TO COMPUTER NETWORKS e The internet is one of the biggest WAN in the world. e A Wide Area Network is widely used in the field of Business, government, and education. ' Workstation ,,,,,, [ | Workstation Fig. 1.9 Examples of Wide Area Network: ¢ Mobile Broadband : A 4G network is widely used across a region or country. e Last Mile : A telecom company is used to provide the internet services to the customers in hundreds of cities by connecting their home with fiber. e Private Network : A bank provides a private network that connects the 44 offices. This network is made by using the telephone leased line provided by the telecom company. Advantages of Wide Area Network : Following are the advantages of the Wide Area Network: e Geographical Area : A Wide Area Network provides a large geographical area. Suppose if the branch of our office is in a different city then we can connect with them through WAN. The internet provides a leased line through which we can connect with another branch. ¢ Centralized Data : In case of WAN network, data is centralized. Therefore, we do not need to buy the emails, files or back up servers. e Get Updated Files : Software companies work on the live server. Therefore, the programmers get the updated files within seconds. e Exchange Messages :In a WAN network, messages are transmitted fast. The web application like Facebook, Whatsapp, Skype allows you to communicate with friends. COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.6) INTRODUCTION TO COMPUTER NETWORKS Sharing of Software and resources : In WAN network, we can share the software and other resources like a hard drive, RAM. Global Business : We can do the business over the internet globally. High Bandwidth : If we use the leased lines for our company then this gives the high bandwidth. The high bandwidth increases the data transfer rate which in turn increases the productivity of our company. Disadvantages of Wide Area Network: The following are the disadvantages of the Wide Area Network: Security Issue : A WAN network has more security issues as compared to LAN and MAN network as all the technologies are combined together that creates the security problem. Needs Firewall and Antivirus Software: The data is transferred on the internet which can be changed or hacked by the hackers, so the firewall needs to be used. Some people can inject the virus in our system so antivirus is needed to protect from such a virus. High Setup Cost: An installation cost of the WAN network is high as it involves the purchasing of routers, switches. Troubleshooting problems: It covers a large area so fixing the problem is difficult. 1.3 INTERNETWORK An internetwork is defined as two or more computer network LANs or WAN or computer network segments are connected using devices, and they are configured by a local addressing scheme. This process is known as internetworking. An interconnection between public, private, commercial, industrial, or government computer networks can also be defined as internetworking. An internetworking uses the internet protocol. The reference model used for internetworking is Open System Interconnection(OSI). Types of Internetwork: 1. Extranet : An extranet is a communication network based on the internet protocol such as Transmission Control protocol and internet protocol. It is used for information sharing. The access to the extranet is restricted to only those users who have login credentials. An extranet is the lowest level of internetworking. It can be categorized as MAN, WAN or other computer networks. An extranet cannot have a single LAN, atleast it must have one connection to the external network. Intranet :An intranet is a private network based on the internet protocol such as Transmission Control protocol and internet protocol. An intranet belongs to an organization which is only accessible by the organization's employee or members. The main aim of the intranet is to share the information and resources among the organization employees. An intranet provides the facility to work in groups and for teleconferences. Intranet Advantages: Communication : It provides a cheap and easy communication. An employee of the organization can communicate with another employee through email, chat. Time-saving : Information on the intranet is shared in real time, so it is time-saving. Collaboration : Collaboration is one of the most important advantage of the intranet. The information is distributed among the employees of the organization and can only be accessed by the authorized user. Platform independency :It is a neutral architecture as the computer can be connected to another device with different architecture. Cost Effective : People can see the data and documents by using the browser and distributes the duplicate copies over the intranet. This leads to a reduction in the cost. COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.7) INTRODUCTION TO COMPUTER NETWORKS [1.4 NETWORK TECHNOLOGY - FROM LOCAL TO GLOBAL AND EXAMPLES OF NETWORKS e A computer network is a cluster of computers over a shared communication path that works for the purpose of sharing resources from one computer to another, provided by or located on the network nodes. e Some of the uses of computer networks are the following: Communicating using email, video, instant messaging, etc. YVYVYY Sharing devices such as printers, scanners, etc. Sharing files Sharing software and operating programs on remote systems > Allowing network users to easily access and maintain information Types of Computer Networks 1. Personal Area Network (PAN) 2. Local Area Network (LAN) 3. Wide Area Network (WAN) 4. Wireless Local Area Network (WLAN) 5. Campus Area Network (CAN) 6. Metropolitan Area Network (MAN) 7. Storage Area Network (SAN) 8. System-Area Network (SAN) 9. Passive Optical Local Area Network (POLAN) 10. Enterprise Private Network (EPN) 11. Virtual Private Network (VPN) 12. Home Area Network (HAN) These are explained as following below. 1. Personal Area Network (PAN) : e PAN is the most basic type of computer network. This PDA Smartphone network is restrained to a single person, that is, communication between the computer devices is ffi fifl centred only to an individual’'s work space. Laptop e PAN offers a network range of 10 meters from a person i ), - Z to the device providing communication. \§ J e Examples of PAN are USB, computer, phone, tablet, Tablet Printer printer, PDA, etc. Fig. 1.10 2. Local Area Network (LAN) : e LAN is the most frequently used network. A LAN is a Computer computer network that connects computers together through a common communication path, contained within a limited area, that is, locally. Computer e A LAN encompasses two or more computers connected P over a server. The two important technologies involved in this network are Ethernet and Wi-fi. e Examples of LAN are networking in a home, school, library, laboratory, college, office, etc. Computer Computer Computer Fig. 1.11 COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.8) INTRODUCTION TO COMPUTER NETWORKS 3. Wide Area Network (WAN) : Computer Computer e WAN is a type of computer network that connects computers over a large geographical distance through Computer LAN Computer Server a shared communication path. e It is not restrained to a single Computer Computer location but extends over many locations. e WAN can also be defined as a group of local area networks Computer that communicate with each other. e The most common example of Computer Server WAN is the Internet. Computer Fig. 1.12 4. Wireless Local Area Network (WLAN) : e WLAN is a type of computer network that acts as a local Wireless Wireless area network but makes use of wireless network station 1 station2 technology like Wi-Fi. e This network does not allow devices to communicate Access point over physical cables like in LAN but allows devices to communicate wirelessly. Wireless Wireless ¢ The most common example of WLAN is Wi-Fi. station 3 station 4 Fig. 1.13 5. Campus Area Network (CAN) : Building 1 uilding e CAN is bigger than a LAN but smaller than a MAN. This is a type of computer network which is usually used in / \ places like a school or college. e This network covers a limited geographical area that is, it Building 4 CAN Building 2 spreads across several buildings within the campus. e Examples of CAN are networks that cover schools, \ / colleges, buildings, etc. Building 3 Fig. 1.14 COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.9) INTRODUCTION TO COMPUTER NETWORKS 6. Metropolitan Area Network (MAN) : e A MAN is larger than a LAN but smaller than a WAN. This is the type of computer network that connects computers over a geographical distance through a shared communication path over a city, town or metropolitan area. e Examples of MAN are networking in towns, cities, a single large city, large area within multiple buildings, etc. Office Office Residential Residential building 1 building 2 area area Office Office Residential Residential building 3 building 4 area area MAN College College Government Government campu1s block campuzs block building 1 building 2 College College Government Government campuss block campu45 block building 5 building 4 Fig. 1.15 7. Storage Area Network (SAN) : e SAN is a type of computer network that is high speed and connects groups of storage devices to several servers. This network does not depend on LAN or WAN.. Instead, a SAN moves the storage resources from the network to its own high-powered network. A SAN provides access to block-level data storage. e Examples of SAN are a network of disks accessed by a network of servers. Computer || Computer || Computer || Computer || Computer 1 2 3 4 5 LAN Server Server Server Server Server 1 2 3 4 5 SAN Storage Storage Storage Storage Storage device 1 device 2 device 3 device 4 device 5 Fig. 1.16 8. System Area Network (SAN) : e A SAN is a type of computer network that connects a cluster of high-performance computers. It is a connection- oriented and high bandwidth network. A SAN is a type of LAN that handles high amounts of information in large requests. This network is useful for processing applications that require high network performance. Microsoft SQL Server 2005 uses SAN through virtual interface adapter. COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.10) INTRODUCTION TO COMPUTER NETWORKS Server cluster Server cluster o000 000 o000 000 000 00 00 000 000 000 Cluster I|nk 000 000 00 00 000 000 000 00 00 00 000 000 00 000 o000 o000 o000 o000 Fig. 1.17 Passive Optical Local Area Network (POLAN) : A POLAN is a type of computer network which is an alternative to a LAN. POLAN uses optical splitters to split an optical signal from a single strand of single mode optical fibre to multiple signals to distribute users and devices. In short, POLAN is a point to multipoint LAN architecture. == OLT Optical L Splltt}}/ f~ o e saas Optical fibre Core switch Optical fibre ™ Distribution feeder Fig. 1.18 10. Enterprise Private Network (EPN) : EPN is a type of computer network mostly used by businesses that want a secure connection over various locations to share computer resources. ISP Enterprise (Internet Enterprise building service building. provider) Private communication line Fig. 1.19 11. Virtual Private Network (VPN) : A VPN is a type of computer network that extends a private network across the internet and lets the user send and receive data as if they were connected to a private network even though they are not. Through a virtual point-to-point connection users can access a private network remotely. VPN protects you from malicious sources by operating as a medium that gives you a protected network connection. File server Home Firewall | | Office | ——— user Internet Remote Remote - Worker Fig. 1.20 COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.11) INTRODUCTION TO COMPUTER NETWORKS 12. Home Area Network (HAN) : e Many of the houses might have more than a computer. To interconnect those computers and with other peripheral devices, a network should be established similar to the local area network (LAN) within that home. Such a type of network that allows a user to interconnect multiple computers and other digital devices within the home is referred to as Home Area Network (HAN). HAN encourages sharing of resources, files, and programs within the network. It supports both wired and wireless communication. Internet Mobile devices Router/ modern Printer Laptop Fig. 1.21 1.5 NETWORK PROTOCOLS e Communication and the exchange of information are the most important and powerful skills in today's modern world. Computer networking is the interconnection of multiple computers and devices by cables and satellites, allowing them to share information, resources, databases, and more regardless of the distance between them. e To ensure efficient and secure communication within networks, many protocols were designed. A protocol is a set of rules that define how communication occurs in a network. e Essentially, it allows connected devices to communicate with each other, regardless of any differences in their internal processes, structure, or design. We can easily communicate with people all over the world by using various network protocols, and thus it plays a critical role in modern digital communications. 1.5.1 Ethernet e Ethernet is a protocol made for Local Area Networks (LAN). It was first standardized in 1983 as IEEE 802.3 and used with thick single coaxial cable 10BASE-5. Start of Frame check frame Destination Source. sequence Preamble (SOF) address address Data + padding (FCS) 7 1 6 6 [46 bytes to 4 bytes bytes bytes bytes 1500 bytes] bytes FC D/l Address Address Address SC Address Frame body FCS 2 2 6 6 6 2 6 [0 bytes to 64 bytes bytes bytes bytes bytes bytes bytes 2312 bytes] bytes FC = Frame control D/I = Duration/Connection ID SC = Sequence Control FCS = Frame check Sequence Fig. 1.22 COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.12) INTRODUCTION TO COMPUTER NETWORKS The Ethernet 802.3 protocol defines the physical layer in wired networking models, as well as the Medium Access Control (MAC) sub-layer of the data link layer. There are several versions of the IEEE 802.3 protocol, e.g., 802.3a, 802.3i, 802.3j. Each version is designed to work on different types of cables. Another widely used protocol is IEEE 802.11, which specifies the physical layer and Media Access Control (MAC) protocols for implementing Wireless Local Area Network (WLAN). This protocol is a wireless computer networking standard and used to allow laptops and smartphones to communicate without being connected with a cable. Let us see the frame format of Ethernet 802.3 and Ethernet 802.11 protocols: The main differences between 802.3 and 802.11 are in the frames sizes, the fields, and the size of transported data. Ethernet 802.11 protocol has two more address fields than the 802.3, and its frame body size is larger than 802.3 (a maximum of 1500 bytes for 802.3 and 2312 bytes for 802.11). 1.5.2 Internet Protocol (IP) Standardized by IEEE in 1974, this protocol is responsible for addressing and fragmenting data packets in digital networks. Its goal is to ensure the successful delivery of packets from source to destination. For this purpose, the IP specifies a format that defines the type of description of data packets called IP datagrams. The first major version of IP is IPv4, and it was first deployed on SATNET in 1982. It uses a 32-bit address space. The latest version of the internet protocol, IPv6, uses 128-bit address space to create unique TCP/IP address identifiers. Let's see the header format for IPv4 and IPv6: Bits 0-3 4-7 8-11 12-15 16 -18 19-23 24 - 27 28-31 0 Version | Header Type of Total Packet Length Length Service (ToS) 32 Identification Flag Fragment Offset 64 Time to Live (TTL) Protocol Checksum Header 96 Source Address 128 Destination Address 160 Options IPv4 Header Bits 0-3 4-7 8-11 12-15 16 - 18 19-23 24 - 27 28-31 0 Version Traffic Class Flux Identification 32 Data Length Next Header Hop-Limit 64 Source Address 128 192 Destination Address 256 IPv6 Header The main difference between IPv4 and IPv6 is the use of address space. The difference between these two can be found in the header, where multiple fields are present in one header but absent from the other. The IPv4 format was reviewed and improved to IPv6, which is more efficient and less complicated. COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.13) INTRODUCTION TO COMPUTER NETWORKS 1.5.3 Internet Control Message Protocol (ICMP) ICMP protocol is made to send error messages in a network. It works with the IP protocol. It helps to diagnose network communication issues. ICMP is mainly used to determine whether or not data is reaching its specified destination in the best ways. Let us see what the ICMP header looks like: Bits 0-7 8-15 16 -2 24 -31 0 Type Code Checksum 32 Header information Since this protocol sends error messages, those errors are determined by a code and type. A checksum specifies the message's precision, and further information about the error will be saved in the header information field. Unlike IP, ICMP is a connectionless protocol. To send an ICMP message from one system to another, it is not needed to establish a connection between systems. Generally, ICMP is found on network devices like routers. It is also used in Distributed Denial-of-Service(DDoS) attacks. 1.5.4 Address Resolution Protocol (ARP) Computer applications use the logical address to communicate with other applications. But to communicate with other applications, we need a physical address (MAC address). This is where we need the Address Resolution Protocol (ARP). It maps network addresses to the physical addresses used by a data link protocol. It is the process of finding an address of a computer in a network. The ARP translates addresses of the network layer to addresses of the data link layer from the OSI networking model. Let us see an example of an ARP message for MAC hardware address resolving: 0 - 8 bits 9 - 15 bits 16 - 31 bits Hardware Type Protocol Type Hardware Address Protocol Address Operation Length (HLEN) Length (PLEN) Sender HA (bytes 4 - 5) Sender IP (bytes 0 - 1) Sender HA (bytes 4 - 5) Target HA (6 bytes) Target HA (bytes 0 - 1) Target IP (bytes 0 - 3) The ARP is one of the most important pillars in the networking process, and it is commonly used with the IP protocols suite. 1.5.5 Transmission Control Protocol (TCP) The Transmission Control Protocol (TCP) is a standard that defines how to establish and maintain a network connection through which application programs can exchange data. It is used on the top of IP to provide reliable transmission of packets. TCP is a connection-oriented reliable protocol. Two devices need to establish a connection before start using TCP and sending the data. It also provides an acknowledgment to the sender device regarding the status of the data being sent. So in case, the sender receives a negative acknowledgment, it resends the data: COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.14) INTRODUCTION TO COMPUTER NETWORKS e During the data transmission, some data may get lost, or some error may occur. e TCP provides an error-checking and recovery mechanism to handle such situations. Sender Receiver Fig. 1.23 e Because TCP uses the direct connection, TCP packet header must contain source and destination port information to exchange messages within a network: Source port (16 bits) Destination port (16 bits) Sequence number(32 bits) Acknowledgment number(32 bits) Data Reserved : offset (4 bits) || (3 bits) || 29° (O PIts) Window (16 bits) Checksum (16 bits) Urgent pointer (16 bits) Options (32 bits) Fig. 1.24 ¢ We can find many applications for the TCP protocol, including the secure shell, the file transport protocol, and the web accessing through the HTTP, World Wide Web (WWW), and email. 1.5.6 User Datagram Protocol (UDP) e The User Datagram Protocol (UDP) is a transport layer protocol used for communication through internet networks for time-sensitive transmissions. It sends messages without the initiation of a connection, which makes the data transfer real quick. UDP is a connectionless and unreliable protocol. * Unlike TCP, there is no mechanism in UDP for packet recovery in case of packet loss. Also, it doesn’t have any error checking process. But in terms of latency and bandwidth, UDP is more efficient than TCP. e Since TCP keeps a conversation flow between connected devices, Request « there is always the need to synchronize and receive the Response == eee > acknowledgment for the sent messages. Response Pr—— Response L, e However, UDP does not maintain such a connection, which means : 5 : Sender Receiver the sender device will keep sending responses to a request.. Fig. 1.25 without the necessity for an acknowledgment message: e Let us now see how a UDP header looks like: e More differences between UDP and TCP can be found in our Source port Destination port ) 2 bytes 2 bytes comparison between UDP and TCP. e UDP is used in real-time services like video communication, Length 2 bytes Checksum 2 bytes online gaming, live streaming of videos, etc. Fig. 1.26 COMPUTER NETWORK & CLOUD COMPUTING (DBATU) (1.15) INTRODUCTION TO COMPUTER NETWORKS 1.5.7 Hypertext Transfer Protocol (HTTP) The Hypertext Transfer Protocol (HTTP) is the foundation of the World Wide Web (WWW) and is used to load web pages using hypertext links. HTTP is an application layer protocol, which allows the user to see a user-friendly interface designed to transfer information between networked devices. It is the protocol helping applications to communicate with the users. A web client is any user application like a web browser. A server is a computational system usually stored in the cloud. When a web client wants to communicate with a web server through WWW, it sends an HTTP request to the server. As soon as the server receives the request, it processes the request and sends an HTTP response to the client. The client receives the HTTP response. It should be noted that an HTTP request header is not the same as a response header: HTTP Request headers HTTP version URL HTTP Request ||Optional HTTP type Method headers body HTTP request HTTP response HTTP status || Response || Optional HTTP code headers body HTTP Response headers Fig. 1.27 HTTP is a connectionless and stateless protocol. A client and server know each other only during communication. As soon as they complete their communication, both of them forget about each other. It is also media independent. Any data can be sent through HTTP. 1.5.8 Dynamic Host Configuration Protocol (DHCP) This protocol works on IP networks, assigning IP addresses to devices and hosts connected to the network. It also allows them to communicate with each other efficiently. In addition to the IP address, DHCP also assigns the subnet mask, default gateway address, the Domain Name Server (DNS) address, and other pertinent configuration parameters. A client device sends discovery messages through a network to a DHCP server, which sends the client an offer. The client then sends back its request allowing the DHCP server to acknowledge the query: Discover 5 < offer T 8es __ Request | [==occo