NETWORK AND SECURITY-Dr.Poovendran R.pptx

NETWORK AND SECURITY

1. NETWORK AND SECURITY Dr.Poovendran R IT professional

2. NETWORKS What is Network? A computer network is a cluster of computers over a shared communication path that works to share resources from one computer to another, provided by or located on the network nodes. Uses of Computer Networks Communicating using email, video, instant messaging, etc. 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.

3. B asic T erminologies in N etworks Network : A network is a collection of computers and devices that are connected together to enable communication and data exchange. Nodes : Nodes are devices that are connected to a network. These can include computers, Servers, Printers, Routers, Switches, and other devices. Protocol : A protocol is a set of rules and standards that govern how data is transmitted over a network. Examples of protocols include TCP/IP, HTTP, and FTP. Topology : Network topology refers to the physical and logical arrangement of nodes on a network. The common network topologies include bus, star, ring, mesh, and tree.

4. Basic terminologies in networks Service Provider Networks : These types of Networks give permission to take Network Capacity and Functionality on lease from the Provider. Service Provider Networks include Wireless Communications, Data Carriers, etc. IP Address : An IP address is a unique numerical identifier that is assigned to every device on a network. IP addresses are used to identify devices and enable communication between them. DNS : The Domain Name System (DNS) is a protocol that is used to translate human-readable domain names (such as www.google.com) into IP addresses that computers can understand.

5. Basic terminologies in networks Firewall : A firewall is a security device that is used to monitor and control incoming and outgoing network traffic. Firewalls are used to protect networks from unauthorized access and other security threats.

6. Types of area networks The Network allows computers to connect and communicate with different computers via any medium. LAN, MAN, and WAN are the three major types of networks designed to operate over the area they cover. There are some similarities and dissimilarities between them. One of the major differences is the geographical area they cover, i.e. LAN covers the smallest area, MAN covers an area larger than LAN and WAN comprises the largest of all.

7. Types of area networks There are four main types of area networks as follows: Personal Area Network (PAN) Local Area Network (LAN) Metropolitan Area Network (MAN) Wide Area Network (WAN)

8. Personal Area N etwork (PAN) PAN is a personal area network having an interconnection of personal technology devices to communicate over a short distance. It covers only less than 10 meters or 33 feet of area. PAN has fewer users as compared to other networks such as LAN, WAN, etc. PAN typically uses some form of wireless technology. PAN involves the transmission of data between information devices such as smartphones, personal computers, tablet computers, etc.

9. Local area network (LAN) LAN or Local Area Network connects network devices in such a way that personal computers and workstations can share data, tools, and programs. The group of computers and devices are connected together by a switch, or stack of switches, using a private addressing scheme as defined by the TCP/IP protocol. Private addresses are unique in relation to other computers on the local network. Routers are found at the boundary of a LAN, connecting them to the larger WAN.

10. Metropolitian Area N etwork (MAN) MAN or Metropolitan area Network covers a larger area than that covered by a LAN and a smaller area as compared to WAN. MAN has a range of 5-50km . It connects two or more computers that are apart but reside in the same or different cities. It covers a large geographical area and may serve as an ISP (Internet Service Provider). MAN is designed for customers who need high-speed connectivity. Speeds of MAN range in terms of Mbps. It’s hard to design and maintain a Metropolitan Area Network.

11. Wide Area N etwork (WAN) WAN or Wide Area Network is a computer network that extends over a large geographical area, although it might be confined within the bounds of a state or country. WAN has a range of above 50 km . A WAN could be a connection of LAN connecting to other LANs via telephone lines and radio waves and may be limited to an enterprise (a corporation or an organization) or accessible to the public. The technology is high-speed and relatively expensive.

12. Components Used in Computer N etworking The hardware and software needed to set up computer networks at homes and businesses are referred to as computer network components. The server, client, peer, transmission media, and connecting devices make up the hardware components. The operating system and protocols are examples of software components. Basically, a computer network is made up of several computers connected to one another so that resources and data can be shared. Wireless or cable-based media are used to connect many PCs.

13. Types of Physical Components used in Computer N etworking NIC(Network Interface Card) HUB Router Modem Switch Nodes Media Repeater Server

14. NIC(Network Interface Card) NIC or 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. NIC card is a layer 2 device, which means it works on the network model’s physical and data link layers. Types of NIC Wired NIC: Cables and Connectors use Wired NIC to transfer data. Wireless NIC: These connect to a wireless network such as Wi-Fi, Bluetooth, etc

15. HUB A HUB is a multi-port repeater. Hubs cannot filter data, so data packets are sent to all connected devices. In other words, the collision domain of all hosts connected through Hub remains one. .

16. SWITCH A Switch is a multiport bridge with a buffer and a design that can boost its efficiency(a large number of ports implies less traffic) and performance. A switch is a data link layer device. The switch can perform error checking before forwarding data, which makes it very efficient as it does not forward packets that have errors and forward good packets selectively to the correct port only.

17. Modem A Modem is a short form of Modulator/Demodulator. The Modem is a hardware component/device that can connect computers and other devices such as routers and switches to the internet. Modems convert or modulate the analog signals coming from telephone wire into a digital form that is in the form of 0s and 1s.

18. Router A Router is a device like a switch that routes data packets based on their IP addresses. The router is mainly a Network Layer device. Routers normally connect LANs and WANs and have a dynamically updating routing table based on which they make decisions on routing the data packets. The router divides the broadcast domains of hosts connected through it.

19. Repeater Repeater is an important component of computer networks as it is used to regenerate and amplify signal in the computer networks. Repeaters are used to improve the quality of the networks and they are operated on the Physical Layer of the OSI Model.

20. Server A server is a computer program that provides various functionality to another computer program. The server plays a vital role in facilitating communication, data storage, etc. Servers have more data storage as compared to normal computers. They are designed for the specific purpose of handling multiple requests from clients.

21. NETWORK TOPOLOGY

22. Media It is also known as Link which is going to carry data from one side to another side. This link can be Wired Medium (Guided Medium) and Wireless Medium (Unguided Medium). It is of two types: Wired Media Wireless Media Examples of Wired media are as follows: Ethernet: Ethernet is the most widely used LAN technology, which is defined under IEEE standards 802.3. There are two types of Ethernet: Ethernet straight-through cable (used for two different devices). Ethernet crossover cable (used for two same devices ). 45g

23. Types of wired cable media Fiber Optic Cable: In this data is transferred in the form of light waves. Coaxial Cable: Mainly used for audio and video communications. USB Cable: USB Stands for Universal Serial Bus. Mainly used to connect PCs and smartphones.

24. OSI Layers in networking OSI stands for Open Systems Interconnection, where open stands to say non-proprietary. It is a 7-layer architecture with each layer having specific functionality to perform. All these 7 layers work collaboratively to transmit the data from one person to another across the globe. The OSI reference model was developed by ISO – ‘International Organization for Standardization‘, in the year 1984.

25. 7 Layers of OSI Model The OSIs Model, or Open Systems Interconnection ,

26. Comparison of the 7 Layers of OSI Model Purpose and Functions Hardware Devices & Protocols Common Problems OSI Layer 1: Physical Data’s physical and electrical transmission over a network connection Network cards, hubs, switches, routers, etc. Protocols include Ethernet and PPP Faulty connections between two nodes, inadequate bandwidth OSI Layer 2: Data Link Providing reliable link-level data transfer between two nodes Network cards, hubs, switches, routers, etc. Protocols used include Ethernet and PPP Misconfigured or incompatible hardware devices, protocol mismatch errors OSI Layer 3: Network Routing packets from the source to the destination Network cards, routers, and gateways. Protocols used include IP, ICMP, ARP, OSPF, BGP, etc Inefficient path selection algorithms, incorrect data format or incorrect routing information OSI Layer 4: Transport Providing reliable end-to-end communication between two nodes in a network Network cards, routers, and gateways. Protocols used include TCP and UDP Inefficient path selection algorithms, incorrect data format OSI Layer 5: Session Establishing and maintaining a session between two applications Network cards, routers, and gateways. Protocols used include SNMP, Telnet, and RPC Missing or corrupted session data OSI Layer 6: Presentation Converting data between different formats and ensuring end-to-end data integrity Network cards, routers, and gateways. Protocols used include SSL/TLS, S-HTTP, and SSH Conversions errors caused by incorrect data format or coding errors OSI Layer 7: Application Responsible for providing end-user services, such as file transfer, web browsing, email, and chat. Network cards, servers, gateways. Protocols used include HTTP, FTP, SMTP, and SSL/TLS Misconfigured routers or gateways, inadequate bandwidth, signal interference due to electrical noise or radio waves

27. FUNCTIONS OF PHYSICAL LAYER Hub, Repeater, Modem, and Cables are Physical Layer devices.

28. DATA LINK LAYER The data link layer is responsible for the node-to-node delivery of the message. The main function of this layer is to make sure data transfer is error-free from one node to another, over the physical layer. When a packet arrives in a network, it is the responsibility of the DLL to transmit it to the Host using its MAC address. The Data Link Layer is divided into two sublayers: Logical Link Control (LLC) Media Access Control (MAC)

29. FUNCTIONS OF DATALINK LAYER Framing: Framing is a function of the data link layer. It provides a way for a sender to transmit a set of bits that are meaningful to the receiver. This can be accomplished by attaching special bit patterns to the beginning and end of the frame. Physical addressing: After creating frames, the Data link layer adds physical addresses (MAC addresses) of the sender and/or receiver in the header of each frame. Error control: The data link layer provides the mechanism of error control in which it detects and retransmits damaged or lost frames. Flow Control: The data rate must be constant on both sides else the data may get corrupted thus, flow control coordinates the amount of data that can be sent before receiving an acknowledgment. Access control: When a single communication channel is shared by multiple devices, the MAC sub-layer of the data link layer helps to determine which device has control over the channel at a given time. Switch & Bridge are Data Link Layer devices.

30. NETWORK LAYER The network layer works for the transmission of data from one host to the other located in different networks. It also takes care of packet routing i.e. selection of the shortest path to transmit the packet, from the number of routes available. The sender & receiver’s IP addresses are placed in the header by the network layer. Functions of the Network Layer Routing: The network layer protocols determine which route is suitable from source to destination. This function of the network layer is known as routing. Logical Addressing: To identify each device inter-network uniquely, the network layer defines an addressing scheme. The sender & receiver’s IP addresses are placed in the header by the network layer. Such an address distinguishes each device uniquely and universally.

31. TRANSPORT LAYER The transport layer provides services to the application layer and takes services from the network layer. The data in the transport layer is referred to as Segments. It is responsible for the end-to-end delivery of the complete message. The transport layer also provides the acknowledgment of the successful data transmission and re-transmits the data if an error is found. At the sender’s side: The transport layer receives the formatted data from the upper layers, performs Segmentation, and also implements Flow and error control to ensure proper data transmission. It also adds Source and Destination port numbers in its header and forwards the segmented data to the Network Layer.

32. FUNCTIONS OF TRANSPORT LAYER Segmentation and Reassembly: This layer accepts the message from the (session) layer, and breaks the message into smaller units. Each of the segments produced has a header associated with it. The transport layer at the destination station reassembles the message. Service Point Addressing: To deliver the message to the correct process, the transport layer header includes a type of address called service point address or port address. Thus by specifying this address, the transport layer makes sure that the message is delivered to the correct process.

33. SESSION LAYER This layer is responsible for the establishment of connection, maintenance of sessions, and authentication, and also ensures security. Functions of the Session Layer Session establishment, maintenance, and termination: The layer allows the two processes to establish, use, and terminate a connection. Synchronization: This layer allows a process to add checkpoints that are considered synchronization points in the data. These synchronization points help to identify the error so that the data is re-synchronized properly, and ends of the messages are not cut prematurely and data loss is avoided. Dialog Controller: The session layer allows two systems to start communication with each other in half-duplex or full-duplex.

34. PRESENTATION LAYER The presentation layer is also called the Translation layer. The data from the application layer is extracted here and manipulated as per the required format to transmit over the network. Functions of the Presentation Layer Translation: For example, ASCII to EBCDIC. Encryption/ Decryption: Data encryption translates the data into another form or code. The encrypted data is known as the ciphertext and the decrypted data is known as plain text. A key value is used for encrypting as well as decrypting data. Compression: Reduces the number of bits that need to be transmitted on the network.

35. APPLICATION LAYER At the very top of the OSI Reference Model stack of layers, we find the Application layer which is implemented by the network applications. These applications produce the data to be transferred over the network. This layer also serves as a window for the application services to access the network and for displaying the received information to the user. Example: Application – Browsers, Skype Messenger, etc.

36. Transmission Control Protocol/Internet Protocol. The TCP/IP model  What Does TCP/IP Do? The main work of TCP/IP is to transfer the data of a computer from one device to another. The main condition of this process is to make data reliable and accurate so that the receiver will receive the same information which is sent by the sender.  What is the Difference between TCP and IP? TCP and IP are different protocols of Computer Networks. The basic difference between TCP (Transmission Control Protocol) and IP (Internet Protocol) is in the transmission of data. In simple words, IP finds the destination of the mail and TCP has the work to send and receive the mail. How Does the TCP/IP Model Work? Whenever we want to send something over the internet using the TCP/IP Model, the TCP/IP Model divides the data into packets at the sender’s end and the same packets have to be recombined at the receiver’s end to form the same data, and this thing happens to maintain the accuracy of the data.

37. Ethernet Ethernet is the traditional technology for connecting devices in a wired local area network ( LAN ) or wide area network. It enables devices to communicate with each other via a  protocol , which is a set of rules Ethernet describes how network devices format and transmit data so other devices on the same LAN or campus network can recognize, receive and process the information. An Ethernet cable is the physical, encased wiring over which the data travels Types of Ethernet cables The IEEE 802.3 Working Group approved the first Ethernet standard in 1983. Since then, the technology Classic Ethernet is the original form of Ethernet that provides data rates between 3 to 10 Mbps.

38. WLAN WLAN  stands for  Wireless Local Area Network.  WLAN is a local area network that uses radio communication to provide mobility to the network users while maintaining the connectivity to the wired network. A WLAN basically, extends a wired local area network. WLAN’s are built by attaching a device called the access point(AP) to the edge of the wired network. 

39. Bluetooth Bluetooth is used for short-range wireless voice and data communication. It is a Wireless Personal Area Network (WPAN) technology and is used for data communications over smaller distances.  Bands from 2.4 GHz to 2.485 GHz. Bluetooth stages up to 10 meters. Depending upon the version, it presents information up to at least 1 Mbps or 3 Mbps. Key Features of Bluetooth The transmission capacity of Bluetooth is 720 kbps. Bluetooth is a wireless device. Bluetooth is a Low-cost and short-distance radio communications standard. Bluetooth is robust and flexible.

40. High-level Data Link Control (HDLC) and Point-to-Point Protocol (PPP) The main difference between  High-level Data Link Control (HDLC)  and  Point-to-Point Protocol (PPP)  is that High-level Data Link Control is the bit-oriented protocol, on the other hand, Point-to-Point Protocol is the byte-oriented protocol Features of HDLC: Error detection and correction: HDLC uses error detection and correction mechanisms such as CRCs and acknowledgments to ensure the integrity of the transmitted data. Full-duplex communication. Multiplexing: Features of PPP: Authentication: PPP includes authentication mechanisms such as Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol. Error detection and correction: PPP uses error detection and correction mechanisms such as CRCs and acknowledgments to ensure the integrity of the transmitted data.

41. What is IP Addressing? An  IP address represents an Internet Protocol address. A unique address that identifies the device over the network. It is almost like a set of rules governing the structure of data sent over the Internet or through a local network. An IP address helps the Internet to distinguish between different routers, computers, and websites. It serves as a specific machine identifier in a specific network and helps to improve visual communication between source and destination

42. IP Addressing IP addresses are expressed as a set of four numbers — an example address might be 192.158.1.38. Each number in the set can range from 0 to 255. the full IP addressing range goes from 0.0.0.0 to 255.255.255.255 . Private IP addresses Public IP addresses

43. Internet Protocol Parts of IP Network part:   The network part indicates the distinctive variety that’s appointed to the network. The network part conjointly identifies the category of the network that’s assigned. Host Part:   The host part uniquely identifies the machine on your network. This part of the IPv4 address is assigned to every host.  For each host on the network, the network part is the same, however, the host half must vary.

44. Network layer protocols Every computer in a network has an IP address by which it can be uniquely identified and addressed. An IP address is Layer-3 (Network Layer) logical address Below are some of the types of Network protocols: Transmission Control Protocol (TCP) ... Internet Protocol (IP) ... Hypertext Transfer Protocol (HTTP) ... Simple Mail Transfer Protocol (SMTP) ... Post Office Protocol (POP) and Internet Message Access Protocol (IMAP) ... File Transfer Protocol (FTP) ---

45. Internet Protocol Version 4 (IPv4) IPv4 is 32-bit addressing scheme used as TCP/IP host addressing mechanism. IP addressing enables every host on the TCP/IP network to be uniquely identifiable. 8.8.8.8 Class A   - it uses first octet for network addresses and last Class B   - it uses first two octets for network addresses and last two for host addressing Class C   - it uses first three octets for network addresses and last one for host addressing Class D   - it provides flat IP addressing scheme in contrast to hierarchical structure for above three. Class E   - It is used as experimental. Classless Inter-Domain Routing  (CIDR)

46. Intra domain is any protocol in which Routing algorithm works only within domains on the other hand Inter domain is any protocol in which Routing algorithm works within and between domains S.No Intradomain Routing Interdomain Routing 1. Routing algorithm works only within domains. Routing algorithm works within and between domains. 2. It need to know only about other routers within their domain. It need to know only about other routers within and between their domain. 3. Protocols used in intradomain routing are known as Interior-gateway protocols. Protocols used in interdomain routing are known as Exterior-gateway protocols. 4. In this Routing, routing takes place within an autonomous network. In this Routing, routing takes place between the autonomous networks.

47. Network layer protocols Network Layer is responsible for the transmission of data or communication from one host to another host connected in a network IPv4 is responsible for packetizing, forwarding, and delivery of a packet. Functions of Network Layer Logical Addressing:  Each device on the network needs to be identified uniquely. Therefore network layer provides an addressing scheme to identify the device. It places the IP address of every sender and the receiver in the header. This header consists of the network ID and host ID of the network. Host-to-host Delivery of Data Fragmentation: Routing and Forwarding

48. Network layer protocols Routing and Forwarding

49. Network layer protocols IP (Internet Protocol) IP stands for Internet Protocol. Internet Protocol helps to uniquely identify each device on the network. Internet protocol is responsible for transferring the data from one node to another node in the network. Internet protocol is a connectionless protocol therefore it does not guarantee the delivery of data. For the successful delivery higher level protocols such as TCP are used to guarantee the data transmission. IPv4:  IPv4 provides with the 32 bit address scheme IPv6:  IPv6 is the most recent version of IP. If provided with a 128 but addressing scheme. ARP (Address Resolution Protocol) ARP stands for Address Resolution Protocol. ARP is used to convert the logical address ie . IP address into physical address ie . MAC -address. While communicating with other nodes, it is necessary to know the MAC address or physical address of the destination node. 

50. Network layer protocols Cont …  ICMP ICMP stands for Internet Control Message Protocol. ICMP is a part of IP protocol suite. ICMP is an error reporting and network diagnostic protocol. Feedback in the network is reported to the designated host. Meanwhile, if any kind of error occur it is then reported to ICMP. The ICMP message is of 32 bit. It consists of 3 fields. First field is of 8 bit that states type of message, second field is of 8 bit that states the reason of message and the third field is of 16 but that consists of actual ICMP message. The messages in ICMP are divided into two types. They are given below: Error Message: Error message states about the issues or problems that are faced by the host or routers during processing of IP packet. Query Message: Query messages are used by the host in order to get information from a router or another host.

51.   IGMP IGMP stands for Internet Group Message Protocol. ICMP is a multicasting communication protocol. It utilizes the resources efficiently while broadcasting the messages and data packets. Mobile Internet Protocol (or Mobile IP) Mobile IP  is a communication protocol (created by extending Internet Protocol, IP) that allows the users to move from one network to another with the same IP address. It ensures that the communication will continue without the user’s sessions or connections being dropped. Mobile IP  is a communication protocol (created by extending Internet Protocol, IP) that allows the users to move from one network to another with the same IP address. It ensures that the communication will continue without the user’s sessions or connections being dropped.

52. Unicast and Multicast Routing Unicast :  Unicast is a type of information transfer and it is used when there is a participation of single sender and single recipient. So, in short, you can term it as a one-to-one mapping. For example, a device having IP address 10.1.4.0 in a network wants to send the traffic stream (data packets) to the device with IP address 20.14.4.2 in the other network, then unicast comes into the picture. It is the most common form of data transfer over the networks.  

53. Multicasting  :  Multicasting has one/more senders and multiple recipients participate in data transfer traffic. In multicasting traffic recline between the boundaries of unicast and broadcast. It server’s direct single copies of data streams and that are then simulated and routed to hosts that request it. IP multicast requires support of some other protocols such as  Internet Group

54. Difference between Unicast and Multicast : S.No . Unicast Multicast 1. It has one sender and one receiver. It has one or more senders and multiple receivers. 2. It sends data from one device to single device. It sends data from one device to multiple devices. 3. It works on Single Node Topology. It works on star, mesh, tree and hybrid topology. 4. It does not scale well for streaming media. It does not scale well across large networks. 5. Multiple unicasting utilizes more bandwidth as compared. It utilizes bandwidth efficiently.

55. IPV6 Addresses Internet Protocol version IPv6 was developed by Internet Engineering Task Force (IETF) to deal with the problem of IPv4 exhaustion. IPv6 is a 128-bits address having an address space of 2 128 , which is way bigger than IPv4. IPv6 use Hexa-Decimal format separated by colon (:) . Components in Address format :    There are 8 groups and each group represents 2 Bytes (16-bits).  Each Hex-Digit is of 4 bits (1 nibble) Delimiter used – colon (:)

56. Transition from IPv4 to IPv6 address Dual Stack Routers, Tunneling, and NAT Protocol Translation . These are explained as following below. 

57. 2. Tunneling:   Tunneling is used as a medium to communicate the transit network with the different IP versions.

58. OSI Model and Protocol stack

59. UNIT III Transport and Application Layers

60. T ransport layer protocols T ransport layer protocols are  responsible for ensuring end-to-end communication between devices They also perform error detection

61. Functions of Transport Layer The process to process delivery End-to-end connection between devices Multiplexing and Demultiplexing 1-X ,X-1 Data integrity and error Correction Congestion Control Flow Control

62. Transport Layer Protocols The transport layer is represented majorly by TCP and UDP protocols. Today almost all operating systems support multiprocessing multi-user environments. This transport layer protocol provides connections to the individual ports.  1. UDP UDP stands for  User Datagram Protocol . User Datagram Protocol provides a nonsequential transmission of data. It is a connectionless transport protocol. UDP protocol is used in applications where the speed and size of data transmitted is considered as more important than the security and reliability. User Datagram is defined as a packet produced by User Datagram Protocol. Services provided by User Datagram Protocol(UDP) are connectionless service, faster delivery of messages, checksum, and process-to-process communication.

63. UDP The User Datagram Protocol, or UDP, is a communication protocol used for time-sensitive applications across the Internet for especially time-sensitive transmissions such as video playback or DNS lookups

64. Advantages of UDP UDP also provides multicast and broadcast transmission of data. UDP protocol is preferred more for small transactions such as DNS lookup. It is a connectionless protocol, therefore there is no compulsion to have a connection-oriented network.

65. TCP TCP stands for Transmission Control Protocol. TCP protocol provides transport layer services to applications. TCP protocol is a connection-oriented protocol. A secured connection is being established between the sender and the receiver

66. Advantages of TCP TCP supports multiple routing protocols. TCP protocol operates independently of that of the operating system. TCP protocol provides the features of error control and flow control. TCP provides a connection-oriented protocol and provides the delivery of data.

67. TCP vs UDP

68. Application Layer The application layer is the topmost layer of the OSI model and the TCP/IP model. In TCP/IP model, the application layer is formed by combining the top three layers, i.e., the application layer, the presentation layer, and the session layer. One of the most often used application protocols is HTTP ( HyperText Transfer Protocol), the foundation for the World Wide Web. Domain Name System (DNS),

69. Domain Name System (DNS) A domain name serves as a distinctive identification for a website. To make it simpler for consumers to visit websites, it is used in place of an IP address. A device connected to the internet is given an IP address, which is a numerical identity. It’s used to pinpoint where on the internet a website or gadget is. An application called a DNS resolver is in charge of translating domain names into IP addresses. The DNS resolver contacts a DNS server to seek the IP address associated with a domain name when a user types it into their web browser.

70. World Wide Web (WWW, W3) C ommonly referred to as WWW, W3, or the Web—is a system of interconnected public webpages accessible through the Internet. The World Wide Web -- also known as the web, WWW or W3 -- refers to all the public websites or pages that users can access on their local computers and other devices through the  internet . These pages and documents are interconnected by means of hyperlinks that users click on for information. This information can be in different formats, including text, images, audio and video.

71. Hypertext Transfer Protocol (HTTP) The  Hypertext Transfer Protocol  (HTTP) is the foundation of the World Wide Web, and is used to load webpages using hypertext links. HTTP is an application layer protocol designed to transfer information between networked devices and runs on top of other layers of the network protocol stack.

72. Electronic mail Electronic mail, commonly shortened to “email,” is a communication method that uses electronic devices to deliver messages across computer networks. "Email" refers to both the delivery system and individual messages that are sent and received. Features of email automatic reply to messages. auto-forward and redirection of messages. facility to send copies of a message to many people. automatic filing and retrieval of messages. addresses can be stored in an address book and retrieved instantly. notification if a message cannot be delivered.

73. QoS in Networking Quality of service (QoS)  is the use of mechanisms or technologies that work on a network to control traffic and ensure the performance of critical applications with limited network capacity. It enables organizations to adjust their overall  network traffic  by prioritizing specific high-performance applications. QoS networking technology works by marking packets to identify service types Types of network traffic Bandwidth : The speed of a link. QoS can tell a router how to use bandwidth. For example, assigning a certain amount of bandwidth to different queues for different traffic types. Delay : The time it takes for a packet to go from its source to its end destination. This can often be affected by queuing delay, which occurs during times of congestion and a packet waits in a queue before being transmitted. QoS enables organizations to avoid this by creating a priority queue for certain types of traffic. Loss :   The amount of data lost as a result of  packet loss , which typically occurs due to network congestion. QoS enables organizations to decide which packets to drop in this event. Jitter : The irregular speed of packets on a network as a result of congestion, which can result in packets arriving late and out of sequence. This can cause distortion or gaps in audio and video being delivered.

74. C ent-Server Programming Client A client is a program that runs on the local machine requesting service from the server. A client program is a finite program means that the service started by the user and terminates when the service is completed. Server A server is a program that runs on the remote machine providing services to the clients. When the client requests for a service, then the server opens the door for the incoming requests, but it never initiates the service.

75. Advantages of Client-server networks: Centralized:  Centralized back-up is possible in client-server networks, i.e., all the data is stored in a server. Security:  These networks are more secure as all the shared resources are centrally administered. Performance:  The use of the dedicated server increases the speed of sharing resources. This increases the performance of the overall system. Scalability:  We can increase the number of clients and servers separately, i.e., the new element can be added, or we can add a new node in a network at any time.

76. Congestion Control and Avoidance Congestion Control is a mechanism that controls the entry of data packets into the network, enabling a better use of a shared network infrastructure and avoiding congestive collapse. Congestive-Avoidance Algorithms (CAA) are implemented at the TCP layer as the mechanism to avoid congestive collapse in a network. Congestion avoidance is a mechanism used to control service flows. A system configured with congestion avoidance monitors network resource usage such as queues and memory buffers. When congestion occurs or aggravates, the system starts to discard packets. How to avoid congestion in a network You can often reduce network congestion simply by increasing the available bandwidth so that the network itself will be able to handle more data, and more devices at the same time.

77. UNIT IV NETWORK SECURITY

78. OSI Security Architecture The OSI (Open Systems Interconnection) Security Architecture defines a  systematic approach to providing security at each layer. It defines security services and security mechanisms that can be used at each of the seven layers of the OSI model to provide security for data transmitted over a network. These security services and mechanisms help to ensure the confidentiality, integrity, and availability of the data

79. OSI Security Architecture focuses on these concepts Security Attack:  Security mechanism: A security mechanism is a means of protecting a system, network, or device against unauthorized access, tampering, or other security threats. Security Service: 

80. Security Attacks A security attack is an attempt by a person or entity to gain unauthorized access to disrupt or compromise the security of a system, network, or device. These are defined as the actions that put at risk an organization’s safety. C lassified into 2 sub-categories: A. Passive Attack: Attacks in which a third-party intruder tries to access the message/ content/ data being shared by the sender and receiver by keeping a close watch on the transmission or eave-dropping the transmission is called Passive Attacks. These types of attacks involve the attacker observing or monitoring system, network, or device activity without actively disrupting or altering it B. Active Attacks: Active attacks refer to types of attacks that involve the attacker actively disrupting or altering system, network, or device activity. Active attacks are typically focused on causing damage or disruption, rather than gathering information or intelligence. Here, both the sender and receiver have no clue that their message/ data is modified by some third-party intruder. The message/ data transmitted doesn’t remain in its usual form and shows deviation from its usual behavior.

81. Security Mechanism The mechanism that is built to identify any breach of security or attack on the organization, is called a security mechanism. Security Mechanisms are also responsible for protecting a system, network, or device against unauthorized access, tampering, or other security threats. Security mechanisms can be implemented at various levels within a system or network and can be used to provide different types of security, such as confidentiality, integrity, or availability.

82. E xamples of security mechanisms Encipherment (Encryption) I nvolves the use of algorithms to transform data into a form that can only be read by someone with the appropriate decryption key. Encryption can be used to protect data it is transmitted over a network, or to protect data when it is stored on a device. Digital signature   Security mechanism that involves the use of cryptographic techniques to create a unique, verifiable identifier for a digital document or message, which can be used to ensure the authenticity and integrity of the document or message. Traffic padding   Is a technique used to add extra data to a network traffic stream in an attempt to obscure the true content of the traffic and make it more difficult to analyze. Routing control  allows the selection of specific physically secure routes for specific data transmission and enables routing changes, particularly when a gap in security is suspected.

83. Security Services Security services refer to the different services available for maintaining the security and safety of an organization. They help in preventing any potential risks to security Security services are divided into 5 types: Authentication  is the process of verifying the identity of a user or device in order to grant or deny access to a system or device. Access control  involves the use of policies and procedures to determine who is allowed to access specific resources within a system. Data Confidentiality  is responsible for the protection of information from being accessed or disclosed to unauthorized parties. Data integrity  is a security mechanism that involves the use of techniques to ensure that data has not been tampered with or altered in any way during transmission or storage. Non- repudiation  involves the use of techniques to create a verifiable record of the origin and transmission of a message, which can be used to prevent the sender from denying that they sent the message.

84. Benefits of OSI Architecture : 1. Providing Security: 2. Organising Task: 3. Meets International Standards:

85. Encryption Encryption is the process by which a readable message is converted to an unreadable form to prevent unauthorized parties from reading it. Decryption is the process of converting an encrypted message back to its original (readable) format. 

86. Advanced Encryption Standard (AES) Advanced Encryption Standard (AES)  is a specification for the encryption of electronic data established by the U.S National Institute of Standards and Technology (NIST) it takes 128 bits as input and outputs 128 bits of encrypted cipher text as output.  it is performed using a series of linked operations which involves replacing and shuffling of the input data.

87. Encryption : AES considers each block as a 16 byte (4 byte x 4 byte = 128 ) grid in a column major arrangement. [ b0 | b4 | b8 | b12 | | b1 | b5 | b9 | b13 | | b2 | b6 | b10| b14 | | b3 | b7 | b11| b15 ] Each round comprises of 4 steps : SubBytes ShiftRows MixColumns Add Round Key

88. What Is Public Key Cryptography Public key encryption is also called asymmetric key encryption. As the name itself says, an asymmetric key, two different keys are used for public-key encryption. One key is used for the encryption process, and another key is used for the decryption process. Once the key is decided for encryption and decryption, no other key will be used. One key is called a public key from these two keys, and another one is called a private key.

89. RSA Algorithm in Cryptography RSA algorithm  is an asymmetric cryptography algorithm. Asymmetric actually means that it works on two different keys i.e.  Public Key  and  Private Key.  As the name describes that the Public Key is given to everyone and the Private key is kept private. An example of asymmetric cryptography:  A client (for example browser) sends its public key to the server and requests some data. The server encrypts the data using the client’s public key and sends the encrypted data. The client receives this data and decrypts it. Rivest, Shamir, and Adelman (RSA).

90. Secure Hash Algorithm  Secure Hash Algorithm is a cryptographic algorithm which takes an input and produces a 160-bit (20-byte) hash value. Input  : hello world  Output  : 2aae6c35c94fcfb415dbe95f408b9ce91ee846ed    Password storage . You must  keep records  of all of the username/password combinations people use to access your resources. But if a hacker gains entry, stealing unprotected data is easy. Hashing ensures that the data is stored in a scrambled state, so it's harder to steal.   Digital signatures . A tiny bit of data proves that a note wasn't modified from the time it leaves a user's outbox and reaches your inbox.   Document management . Hashing algorithms can be used to  authenticate data . The writer uses a hash to secure the document when it's complete. The hash works a bit like a seal of approval.A recipient can generate a hash and compare it to the original. If the two are equal, the data is considered genuine. If they don't match, the document has been changed.   File management . Some companies also use hashes to index data, identify files, and delete duplicates. If a system has thousands of files, using hashes can save a significant amount of time. 

91. Digital Signature Algorithm

92. DSA stands for Digital Signature Algorithm. It is a cryptographic algorithm used to generate digital signatures, A Digital Signature is a verification method made by the recipient to ensure the message was sent from the authenticated identity. When a customer signs a check, the bank must verify that he issued that specific check. In this case, a signature on a document acts as a sign of authentication and verifies that the document is authentic. DSA works by having two keys: a private key owned by the sender and a public key held by the receiver.  The sender uses their private key to generate a signature for the message, which is then sent along with it.  Then, the message receiver uses the sender's public key to verify that the signature is valid and that the message has not been tampered with.  The verification process is done using unique algorithms that allow the receiver to validate the signature without having access to the sender's private key.

93. Methods of Digital Signature These two are standard Approaches to implement the Digital Signature: Rivest-Shamir-Adleman (RSA) Digital Signature Algorithm (DSA) Advantages of DSA Integrity - If something is altered in the content after the signature is made, then it becomes invalid Efficiency:  Digital signatures make the process of signing electronic and automate it, giving way to fast online transactions Security:  As long as the whole digital signing process is well organized, digital signatures may prove to be secure. World Acceptance Cost Savings:  The digital signing process discontinues the need for transporting documents

94. Unit V Hardware security practices . Introduction to hardware security. Hardware security is defined as the protection of physical devices from threats that would facilitate unauthorized access to enterprise systems Hardware security is a device that scans employee endpoints or monitors network traffic, such as a hardware firewall or a proxy server. Device-based hardware security is also achieved through hardware security modules (HSM) 

95. Key Threats to Enterprise Hardware B asic input-output systems (BIOS), motherboards, network cards, Wi-Fi cards, hard drives, graphics cards, systems-on-a-chip, and servers 

96. Hardware Trojan In terms of  Hardware security , It is a malicious modification of the circuitry of an IC chip. It is done during the design or fabrication of chip (i.e. The chip is modified without the possible knowledge of the person who designed it. ) It is sometimes also known as  ‘HT’ . A Hardware Trojan or HT is something, a piece of hardware, which is hiding inside another larger piece of hardware. It wakes up at unpredictable times and does something malicious which is again unpredictable with respect to user. 

97. Properties of a Hardware Trojan It can take place pre or post manufacturing. It is inserted by some intellectual adversary. It is extremely small hardware overhead. 4.It causes IC to malfunction in-field. The entire activity that the Trojan performs or executes is known as  payload .

98. Components of a Hardware Trojan