8.1 COMMUNICATIONS

Communications is the exchange of information two or more things, such as people, devices, governments, organizations, or businesses. In digital communication, data is exchanged between two or more computing devices. The collection of digital devices and their connection media is a computer network Examples: For example, modems, cables, and ports are all communications devices.

8.2 NETWORKS

 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. A computer network can be categorized by their size. A computer network is mainly of four types:

• LAN(Local Area Network)
• MAN(Metropolitan Area Network)
• WAN(Wide Area Network)

8.2.1. LANS, MANS AND WANS

LAN (LOCAL AREA NETWORK)

• Local Area Network is a group of computers connected to each other in a small area such as building, office.
• LAN is used for connecting two or more personal computers through a communication medium such as twisted pair, coaxial cable, etc.
• It is less costly as it is built with inexpensive hardware such as hubs, network adapters, and ethernet cables.
• The data is transferred at an extremely faster rate in Local Area Network.
• Local Area Network provides higher security.

MAN(METROPOLITAN AREA NETWORK)

• A metropolitan area network is a network that covers a larger geographic area by interconnecting a different LAN to form a larger network.
• 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.
• The most widely used protocols in MAN are RS-232, Frame Relay, ATM, ISDN, OC-3, ADSL, etc.
• It has a higher range than Local Area Network(LAN).

WAN (WIDE AREA NETWORK)

• A Wide Area Network is a network that extends over a large geographical area such as states or countries.
• A Wide Area Network is quite bigger network than the LAN.
• 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.
• The internet is one of the biggest WAN in the world.
• A Wide Area Network is widely used in the field of Business, government, and education.

8.2.2  NETWORK ARCHITECTURE

Computer Network Architecture is defined as the physical and logical design of the software, hardware, protocols, and media of the transmission of data. Simply we can say that how computers are organized and how tasks are allocated to the computer.

The two types of network architectures are used:

• Peer-To-Peer network
• Client/Server network

PEER-TO-PEER NETWORK

• Peer-To-Peer network is a network in which all the computers are linked together with equal privilege and responsibilities for processing the data.
• Peer-To-Peer network is useful for small environments, usually up to 10 computers.
• Peer-To-Peer network has no dedicated server.
• Special permissions are assigned to each computer for sharing the resources, but this can lead to a problem if the computer with the resource is down.

CLIENT/SERVER NETWORK

• Client/Server network is a network model designed for the end users called clients, to access the resources such as songs, video, etc. from a central computer known as Server.
• The central controller is known as a server while all other computers in the network are called clients.
• A server performs all the major operations such as security and network management.
• A server is responsible for managing all the resources such as files, directories, printer, etc.

All the clients communicate with each other through a server. For example, if client1 wants to send some data to client 2, then it first sends the request to the server for the permission.

8.2.3 NETWORK TOPOLOGIES

Network Topology defines the structure of the network of how all the components are interconnected to each other. Physical topology is the geometric representation of all the nodes in a network.

BUS TOPOLOGY

• The bus topology is designed in such a way that all the stations are connected through a single cable known as a backbone cable.
• Each node is either connected to the backbone cable by drop cable or directly connected to the backbone cable.
• When a node wants to send a message over the network, it puts a message over the network. All the stations available in the network will receive the message whether it has been addressed or not.
• The bus topology is mainly used in 802.3 (ethernet) and 802.4 standard networks.
• The configuration of a bus topology is quite simpler as compared to other topologies.
• The backbone cable is considered as a “single lane” through which the message is broadcast to all the stations.

RING TOPOLOGY

• Ring topology is like a bus topology, but with connected ends.
• The node that receives the message from the previous computer will retransmit to the next node.
• The data flows in one direction, i.e., it is unidirectional.
• The data flows in a single loop continuously known as an endless loop.
• It has no terminated ends, i.e., each node is connected to other node and having no termination point.
• The data in a ring topology flow in a clockwise direction.
• The most common access method of the ring topology is token passing.
• Token passing: It is a network access method in which token is passed from one node to another node.
• Token: It is a frame that circulates around the network.

STAR TOPOLOGY

• Star topology is an arrangement of the network in which every node is connected to the central hub, switch or a central computer.
• The central computer is known as a server, and the peripheral devices attached to the server are known as clients.
• Coaxial cable or RJ-45 cables are used to connect the computers.
• Hubs or Switches are mainly used as connection devices in a physical star topology.
• Star topology is the most popular topology in network implementation.

TREE TOPOLOGY

• Tree topology combines the characteristics of bus topology and star topology.
• A tree topology is a type of structure in which all the computers are connected with each other in hierarchical fashion.
• The top-most node in tree topology is known as a root node, and all other nodes are the descendants of the root node.
• There is only one path exists between two nodes for the data transmission. Thus, it forms a parent-child hierarchy.

MESH TOPOLOGY

• • Mesh technology is an arrangement of the network in which computers are interconnected with each other through various redundant connections.
  • There are multiple paths from one computer to another computer.
  • It does not contain the switch, hub or any central computer which acts as a central point of communication.
  • The Internet is an example of the mesh topology.
  • Mesh topology is mainly used for WAN implementations where communication failures are a critical concern.
  • Mesh topology is mainly used for wireless networks.

HYBRID TOPOLOGY

• • The combination of various different topologies is known as Hybrid topology.
  • A Hybrid topology is a connection between different links and nodes to transfer the data.
  • When two or more different topologies are combined together is termed as Hybrid topology and if similar topologies are connected with each other will not result in Hybrid topology. For example, if there exist a ring topology in one branch of ICICI bank and bus topology in another branch of ICICI bank, connecting these two topologies will result in Hybrid topology.

8.2.4 .INTRANET

An intranet can be defined as a private network used by an organization. Its primary purpose is to help employees securely communicate with each other, to store information, and to help collaborate. Modern intranets use social intranet features that allow employees to create profiles and to submit, like, comment, and share posts.

8.3 NETWORK COMMUNICATION STANDARDS

Network Communication Standards is a set of rules for exchanging information between computers on a network . The devices in a network cannot communicate without a protocol.

8.3.1 ETHERNET

Ethernet is the most common used LAN standard. it is use a high-speed network cable and bus topology. it is inexpensive and easy to install and manage. All computers in ethernet use same cable to send and receive data. They must follow the rules of communication, if two or more computers transmit data at the same the message will be lost. A computer checks if the cable is use before transmitting data. the computer WAITS IF THE cable is being used then it sends the data when cable is free. This process is called carrier sense Multiple access with collision detection (CSMA/CA).

8.3.2 TOKEN RING

Token ring is a network standard that is typically used in Lan. it allows network devices to access the network by passing a special signal called token. Token is like a ticket.Some rules must follow when computer send a message, it gets the token ,Puts the date in the token, Add the address of receiving computer

8.3.3 TCP/IP

TCP/IP originated out of the investigative research into networking protocols that the US Department of Defense (DoD) initiated in 1969. In 1968, the DoD Advanced Research Projects Agency (ARPA) began researching the network technology that is called packet switching. The original focus of this research was that the network be able to survive loss of subnet hardware, with existing conversations not being broken off. In other words, DoD wanted connections to remain intact as long as the source and destination nodes were functioning, even if some of the machines or transmission lines in between were suddenly put out of operation. The network that was initially constructed as a result of this research to provide a communication that could function in wartime, and then called ARPANET, gradually became known as the Internet. The TCP/IP protocols played an important role in the development of the Internet. In the early 1980s, the TCP/IP protocols were developed. In 1983, they became standard protocols for ARPANET.

8.4 COMMUNICATIONS OVER THE TELEPHONE NETWORK

The public switched telephone network (PSTN) is the worldwide telephone system that handles voice-oriented telephone calls (Figure 8-15). Nearly the entire telephone network today uses digital technology, with the exception of the final link from the local telephone company to a home, which often is analog. The telephone network is an integral part of computer communications. Data, instructions, and information are transmitted over the telephone network using dial-up lines or dedicated lines. The following sections discuss dial-up lines and the various types of dedicated lines that use the telephone network for data communications.

 8.4.1 DIAL-UP LINES

A dial-up line is a temporary connection that uses one or more analog telephone lines for communications. A dial-up connection is not permanent. Using a dial-up line to transmit data is similar to using the telephone to make a call. A modem at the sending end dials the telephone number of a modem at the receiving end. When the modem at the receiving end answers the call, a connection is established and data can be transmitted. When either modem hangs up, the communications end.

8.4.2 DEDICATED LINES

A dedicated line is a type of always-on connection that is established between two communications devices (unlike a dial-up line where the connection is reestablished each time it is used). The quality and consistency of the connection on a dedicated line are better than a dial-up line because dedicated lines provide a constant connection. Businesses often use dedicated lines to connect geographically distant offices. Dedicated lines can be either analog or digital. Digital lines increasingly are connecting home and business users to networks around the globe because they transmit data and information at faster rates than analog lines.

8.4.3 ISDN LINES

ISDN lines for the small business and home user, an ISDN line provides faster transfer rates than dial-up telephone lines. Not as widely used today as in the past, ISDN (Integrated Services Digital Network) is a set of standards for digital transmission of data over standard copper telephone lines. ISDN requires that both ends of the connection have an ISDN modem.

8.4.4 DSL

DSL is a popular digital line alternative for the small business or home user. DSL (Digital Subscriber Line) transmits at fast speeds on existing standard copper telephone wiring. Some DSL installations include a dial tone, providing users with both voice and data communications.

8.5 COMMUNICATION DEVICE

A communication device is a hardware device capable of transmitting an analog or digital signal over the telephone, other communication wire, or wirelessly.

8.5.1 DIAL-UP MODEM

A dial-up modem transmits computer data over an ordinary switched telephone line that has not been designed for data use. This contrasts with leased line modems, which also operate over lines provided by a telephone company, but ones which are intended for data use and do not impose the same signaling constraints.

8.5.2 WIRELESS MODEM

It is used to access the Web without wire form notebook and handheld computers, cellular phones and other mobile devices. Some mobile users have a wireless modem that uses the cell phone network to connect to the Internet wirelessly from  a notebook computer, a smart phone, or other mobile device.

8.5.3 NETWORK INTERFACE CARD

Network Interface Card (NIC) is also called LAN adapter. It is used to connect a device to a network. It also used for the management of instructions, the transmission of data, and information to and from the computer with NIC.

8.5.4 ROUTER

A router is a communications device that connects multiple computers or other routers together and transmits data to its correct desti- nation on the network. A router can be used on any size of network. On the largest scale, routers along the Internet backbone forward data packets to their destination using the fastest available path. For smaller business and home networks, a router allows multiple computers to share a single high-speed Internet connection.

8.5.5 HUB AND SWITCHES

• HUB

A Hub is a networking device that allows you to connect multiple PCs to a single network. It is used to connect segments of a LAN. A hub stores various ports, so when a packet arrives at one port, it is copied to various other ports. Hub works as a common connection point for devices in a network.

• SWITCH

A network switch is a computer networking device that connects various devices together on a single computer network. It may also be used to route information in the form of electronic data sent over networks. Since the process of linking network segments is also called bridging, switches are usually referred to as bridging devices.

8.6 COMMUNICATIONS CHANNELS

A communication channel is the medium used to transport information from one network device to another. Wired channels transport data through wires and cables. Wireless channels transport data from one device to another without the use of cable or wires.

8.7 PHYSICAL TRANSMISSION MEDIA

Physical transmission media used in communications include twisted-pair cable, coaxial cable, and fiber-optic cable. These cables typically are used within or underground between buildings. Ethernet and token ring LANs often use physical transmission media.

8.7.1 TWISTED-PAIR CABLE

One of the more commonly used transmission media for network cabling and telephone systems is twisted-pair cable. Twisted-pair cable consists of one or more twisted-pair wires bundled together. Each twisted-pair wire consists of two separate insulated copper wires that are twisted together. The wires are twisted together to reduce noise. Noise is an electrical disturbance that can degrade communications.

 8.7.2 COAXIAL CABLE

Coaxial cable, often referred to as coax (pronounced KO-ax), consists of a single copper wire surrounded by at least three layers: (1) an insulating material, (2) a woven or braided metal, and (3) a plastic outer coating .

8.7.3 FIBER-OPTIC CABLE

The core of a fiber-optic cable consists of dozens or hundreds of thin strands of glass or plastic that use light to transmit signals. Each strand, called an optical fiber, is as thin as a human hair. Inside the fiber-optic cable, an insulating glass cladding and a protective coating surround each optical fiber

8.8 WIRELESS TRANSMISSION MEDIA

Many users opt for wireless transmission media because it is more convenient than installing cables. In addition, businesses use wireless transmission media in locations where it is impossible to install cables. Types of wireless transmission media used in communications include infrared, broadcast radio, cellular radio, microwaves, and communications satellites.

8.8.1 INFRARED

As discussed earlier in the chapter, infrared (IR) is a wireless transmission medium that sends signals using infrared light waves. Mobile computers and devices, such as a mouse, printer, and smart phone, often have an IrDA port that enables the transfer of data from one device to another using infrared light waves.

8.8.2 BROADCAST RADIO

Broadcast radio is a wireless transmission medium that distributes radio signals through the air over long distances such as between cities, regions, and countries and short distances such as within an office or home.

8.8.3 CELLULAR RADIO

Cellular radio is a form of broadcast radio that is used widely for mobile communications, specifically wireless modems and cell phones. A cell phone is a telephone device that uses high-frequency radio waves to transmit voice and digital data messages.

8.8.4 Microwaves

Microwaves are radio waves that provide a high-speed signal transmission. Microwave transmission, often called fixed wireless, involves sending signals from one microwave station to another. Microwaves can transmit data at rates up to 4,500 times faster than a dial-up modem. A microwave station is an earth-based reflective dish that contains the antenna, transceivers, and other equipment necessary for microwave communications. Microwaves use line-of-sight transmission. To avoid  possible obstructions, such as buildings or mountains, microwave stations often sit on the tops of buildings, towers, or mountains.

8.8.5 COMMUNICATIONS SATELLITE

A communications satellite is a space station that receives microwave signals from an earth-based station, amplifies (strengthens) the signals, and broadcasts the signals back over a wide area to any number of earth-based stations. These earth-based stations often are microwave stations. Other devices, such as smart phones and GPS receivers, also can function as earth-based stations. Transmission from an earth-based station to a satellite is an uplink. Transmission from a satellite to an earth-based station is a downlink.

8.9 INTERNET AND NETWORK ATTACKS

• NETWORK ATTACK

Actions taken through the use of computer networks to disrupt, deny, degrade, or destroy information resident in computers and computer networks, or the computers and networks themselves.

• INTERNET ATTACK

A cyber-attack is any type of offensive action that targets computer information systems, infrastructures, computer networks or personal computer devices, using various methods to steal, alter or destroy data or information systems.

8.9.1 COMPUTER VIRUSES, WORMS, TROJAN HORSE AND ROOTKITS

• COMPUTER VIRUSES

A computer virus is a malicious piece of computer code designed to spread from device to device. A subset of malware, these self-copying threats are usually designed to damage a device or steal data.

• COMPUTER WORMS

A computer worm is a type of malware that spreads copies of itself from computer to computer. A worm can replicate itself without any human interaction, and it does not need to attach itself to a software program in order to cause damage.

• TROJANS

As in the myth, a Trojan is a virus that hides within a legitimate-seeming program to spread itself across networks or devices. Ransomware – Ransomware is a type of malware that encrypts a user’s files and demands a ransom for its return.

• ROOTKIT

A rootkit is a clandestine computer program designed to provide continued privileged access to a computer while actively hiding its presence. … Today rootkits are generally associated with malware such as Trojans, worms, viruses  that conceal their existence and actions from users and other system processes.

8.9.2 SAFEGUARDS AGAINST COMPUTER VIRUSES AND OTHER MALWARE

One of the most important ways to protect against malware is to install anti-virus software. Anti-virus software will protect your device from malicious software that poses a threat to the system. How to prevent computer virus and malware

1. Keep your computer and software updated. …
2. Use a non-administrator account whenever possible. …
3. Think twice before clicking links or downloading anything. …
4. Be careful about opening email attachments or images. …
5. Don’t trust pop-up windows that ask you to download software. …
6. Limit your file-sharing.

8.9.3 BOTNET

A botnet (short for “robot network”) is a network of computers infected by malware that are under the control of a single attacking party, known as the “bot-herder.” Each individual machine under the control of the bot-herder is known as a bot. … They are also used to spread bots to recruit more computers to the botnet.

8.9.4 DENIAL OF SERVICE ATTACK

A Denial-of-Service (DoS) attack is an attack meant to shut down a machine or network, making it inaccessible to its intended users. DoS attacks accomplish this by flooding the target with traffic ,or sending it information that triggers a crash.

8.9.5 SPOOFING

Spoofing is the act of disguising a communication from an unknown source as being from a known, trusted source. Spoofing can apply to emails, phone calls, and websites, or can be more technical, such as a computer spoofing an IP address, Address Resolution Protocol (ARP), or Domain Name System (DNS) server. An example of spoofing is when an email is sent from a false sender address, that asks the recipient to provide sensitive data. This email could also contain a link to a malicious website that contains malware.

8.9.6 SAFEGUARDS AGAINST BOTNET, DOS/DDOS ATTACK,BACK DOOR AND SPOOFING

• BOTNET

The following tips will help you become a moving target and prevent your devices from turning into evil bots.

1. Keep your systems and apps up to date.
2. Use a reliable antivirus tool.
3. Stay away from dubious email attachments.
4. Use a firewall.
5. Say no to pirated software.

• DOS/DDOS ATTACKS

Strengthen their security posture: This includes fortifying all internet-facing devices to prevent compromise, installing and maintaining antivirus software, establishing firewalls configured to protect against DoS attacks and following robust security practices to monitor and manage unwanted traffic. Best DDoS protection of 2021

• Project Shield.
• Cloudflare.
• AWS Shield.
• Microsoft Azure.
• Verisign DDoS Protection/ Neustar.

• BACKDOOR

Backdoors are difficult to detect. Everyday users can’t discover a backdoor just by opening the Task Manager. But there are a few easy steps you can take to keep your device safe from backdoors virus attacks, such as:

• Use an Antivirus
• Download with Care
• Use a Firewall
• Use a Password Manager
• Stay on Top of Security Updates/Patches

• SPOOFING

 To protect yourself against spoofing attacks:

• Stay sharp
• Call to confirm
• Be wary of strange attachments
• Hide your IP address
• Regularly change your passwords
• Check before you click
• Report spoofing attempts
• Use a dedicated secure browser
• Use strong antivirus protection

8.9.7 FIREWALL

In computing, a firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted network and an untrusted network, such as the Internet.

8.9.8 INTRUSION DETECTION SYSTEM

An intrusion detection system (IDS) is a device or software application that monitors a network for malicious activity or policy violations. Any malicious activity or violation is typically reported or collected centrally using a security information and event management system.

8.10 HARDWARE THEFT AND VANDALISM

Hardware theft means stealing the computer equipment and hardware vandalism is when the computer equipment is being destroyed or defaced, for example, cutting a computer cable or breaking a computer screen.

8.10.1 SAFEGUARDS AGAINST HARDWARE THEFT AND VANDALISM

To reduce the amount of hardware theft, here are some safeguards against hardware theft and vandalism are as follows:

• Physical access control. Put the hardware in a safe place and secure it by locking the place and protect the equipment.
• Real time location. System of tracking and identifying the location of high-risk or high-value items.
• Install alarm systems. When someone breaks into the safe room at a time where he is not allowed to and tries to steal or break hardware for example, the alarm will let the security forces know.
• Use cables to lock computers to stationary objects. That way, it will not be easy to move the computer.
• Install a mini security system. Same as the alarm system.

8.11 SOFTWARE THEFT

Software theft means the unauthorized or illegal copying, sharing or usage of copyright-protected software programs. Software theft is committed when someone performs any of the following: Steals software media. Deliberately erases programs. Illegally copies or distributes a program

8.11.1 SAFEGUARDS AGAINST SOFTWARE THEFT

Use physical access controls to your hardware such as locked doors and windows. Use cables to lock. Your equipment to a table, desk, or floor. Never leave a notebook computer or mobile device unattended in a public place. Use passwords, possessed objects, and biometrics as a method of security.

8.12 INFORMATION THEFT

Information theft is the act of stealing digital information stored on computers, servers, or electronic devices of an unknown victim with the intent to compromise privacy or obtain confidential information.

8.12.1 SAFEGUARD AGAINST INFORMATION THEFT

Putting all your important documents in a safe can protect your information from getting into the wrong hands.  Keep your Social Security card, passport, birth certificate, extra checks, copies of your health insurance cards, and a printed page of your important passwords in a safe.

8.12.2 ENCRYPTION

Encryption is a means of securing digital data using one or more mathematical techniques, along with a password or “key” used to decrypt the information. For example, websites that transmit credit card and bank account numbers should always encrypt this information to prevent identity theft and fraud.

8.13 INFORMATION PRIVACY

Information privacy is the privacy of personal information and usually relates to personal data stored on computer systems.The need to maintain information privacy is applicable to collected personal information, such as medical records, financial data, criminal records, political records, business related information or website data. Information privacy is also known as data privacy.

8.13.1 COOKIES

A cookie typically contains two bits of data: a unique ID for each user, and a site name. Cookies enable websites to retrieve this information when you revisit them, so that they can remember you and your  preferences and tailor page content for you based on this information

8.13.2 SPAM

Spam refers to unsolicited bulk messages being sent through email, instant messaging or other digital communication tools. Beyond being a simple nuisance, spam can also be used to collect sensitive information from users and has also been used to spread viruses and other malware.

8.13.3 PHISHING

Phishing attacks are the practice of sending fraudulent communications that appear to come from a reputable source. It is usually done through email. The goal is to steal sensitive data like credit card and login information, or to install malware on the victim’s machine.

8.13.4 SPYWARE AND ADWARE

Spyware is basically any technology that helps gather information about a computer user without their knowledge. Adware is any software with banner advertisements displayed while it is running. Malware is any software that is harmful to a computer user, such as a virus or spyware.

8.13.5 PRIVACY LAW

The Privacy Act regulates the way individuals’ personal information is handled. As an individual, the Privacy. Act gives you greater control over the way that your personal information is handled.