Computer Network

Computer Network

by Ashish Bhatnagar

​Computer Network

• ​Two or more computers that are connected with one another for the purpose of communicating data electronically.

• ​Communication can be for the purpose of sharing data and resources or for communication

​MODEM

• ​Modulator and Demodulator device

• ​Converts digital signals from a computer to analog signal for transmission over telephone lines and vice versa.

• ​Dial-up modems establishes a connection with the internet over a normal voice call. Dial up connection needs to be established manually.

• ​Dial up modem has very slow speed of data transfer

• Voice call cannot be made during the internet connection.​

• ​Broadband modem uses a dedicated line for internet connection. It is always on connection and provides high speed data transfer.

• ​Internet access and voice calls can be used simultaneously.

​Network Hub

• A network hub provides interconnection between several computer or devices in a computer network.​

• A hub receives the data from a computer and sends it to all the computers connected to the network. Only the intended computer accepts the data.​

• ​Hub is less efficient and smart device.

• ​Used due to low cost.

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​Network Switch

• ​A network switch serves the same purpose as a network hub.

• ​It is more efficient than a network hub because it sends the data only to the intended computer.

• ​A network switch has a table containing the network addresses of all the devices connected to the network.

• Each device has a MAC address for identification.​

• ​Switch is expensive as compared to a hub

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​Bridge

• ​A bridge is used to connect two different networks with each other.

• ​Networks using the same technology can only be connected using a bridge.

• ​Bridging connects two separate networks as if they were a single network.

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​Router

• A router is a device that connects two or more networks.

• It serves two primary functions: managing traffic between these networks by forwarding data packets to their intended IP addresses, and allowing multiple devices to use the same Internet connection.​

• ​A router forms networks and manages the flow of data within and between those networks

• Router directs the data between the internet and several devices connected to it. It also creates a local network for data transfer between these devices.

• Sending the data to a specific device is done by the help of MAC address​ which is unique to each device.

Internet Protocol Address

It helps to identify a network connection

Logical Address of a connection

IP address is provided by the network provider​

IP Address

Media Access Control Address

It is a unique address that is assigned to a Network Interface Card

Mostly a MAC address is given in hexadecimal format

MAC address is given by the manufacturer of the device

MAC is the identity of a device

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MAC Address

MAC and IP Address

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Poll

Hub is a smart network device.

• True

• False

Data Packets

• When data has to be transmitted over the network, it is broken down into smaller part called packets.

• Once the data packets reach their destination, they are assembled back into complete set of data

• Data packet contains source IP address

• Destination IP address

• Sequence number of the packet​

Gateway

-A gateway is a node (router) in a computer network, a key stopping point for data on its way to or from other networks.

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-For basic Internet connections at home, the gateway is the Internet Service Provider that gives you access to the entire Internet.

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​-For the wireless network at home that gives your entire family access to the Internet, router is your gateway to the internet.

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Network Interface Card

-Also called network interface controller, network adapter or LAN adapter.

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- It provides a connection port in the device for connecting to the network.

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- Each NIC has a unique and fixed MAC address that is used to identify the device on the network.

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-allows communications between computers connected via local area network (LAN) as well as communications over large-scale network through Internet Protocol (IP).​

​Bluetooth

It provide wireless connectivity from wireless headphones to mobile phones, laptops & mice of the wireless computer to a lot of other devices which need a short-range of connectivity.

It utilizes 79 different frequencies or channels for communication.

Device can pick up any channel which is not being utilized by an other device in it's vicinity

Channels are constantly changed to avoid interference

Suitable for short distance, low speed and low bandwidth communication.​

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ICT

Network Devices

WiFi

Commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio waves

Wi-Fi's wavebands have relatively high absorption and work best for line-of-sight use. Many common obstructions such as walls, pillars, home appliances, etc. may greatly reduce range.

It provides faster data transmission rates, increased signal range and higher levels of security as compared to a Bluetooth signal​

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Local Area Network

LAN is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building.

Network is used for sharing of hardware and software resources and for communication

All the computers can be controlled from the main server by a network administrator​

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Local Area Network

Easier spread of viruses through the computer network.

Slower access to external networks such as internet​

Increased security risk when compared to standalone computers

Server breakdown can bring down the whole network.​

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Wide Area Network

Computers are spread over a large geographical area as compared to a LAN.

A number of LANs connected together by a router can make a WAN.

WAN networks can utilize the telephone network for communication due to longer distances.

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Wireless LANs

A LAN providing connectivity via wireless signals like radio waves or infra red signals

Access Points are connected to a wired network to provide network connectivity to the network

Devices can access the network from anywhere without the mess of cables running around

Adding new computers is very easy and cheaper because cabling is not required.

Slower data transfer speed as compared to a cable connection​

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Internet Policing

• Help in prevention of illegal activities on internet.

• Preventing dangerous information to be easily available like bomb making, ​hacking techniques.

• Stop ​kids from getting exposed to undesirable websites

• ​Stop incorrect information being published online

• Stop distribution of copyright material

• ​Stop spreading of computer viruse

Internet Policing

• Policing the websites would be very expensive and users have to bear the cost making internet less accessible.

• Difficult to enforce similar rules and regulations across the globe.

  ​It can go against freedom of speech and information

• ​Laws and regulations already exist to deal with negativity on internet.

• Information available can be controlled by powerful people and companies in order to favor them.​

Quality of information

• There are several factors to be considered when someone is using a search engine like google to search for some information.

  • ​Reliability of information

  • ​Undesirability of websites

  • ​Security issues

Reliability of Information

• Information on internet is more updated than in a book.

• ​Easier and faster to get information from internet

• Vast amount of information is available for a topic

• ​Cheaper to get information from internet

• ​Information can be incorrect if it is not properly vetted before release.

• ​Information overload. Due to large amount of information available, it can get difficult to choose which one to use.​

Undesirability of websites

• Risk of finding undesirable websites

• ​Fake websites that links to irrelevant and even harmful content.

• ​Fake websites posing as some other websites and tracking your data or even stealing personal information.

• Downloading malicious code disguised in a useful application​

Security Issues

• Risk of downloading malicious code like a virus or spying application, keylogger etc.

• Stealing personal information like username and passwords, credit card details etc.

• ​Scamming the customer by overcharging the credit card

Strong Password

• Use a password that doesn't use your personal details like last name, date of birth, name of pet etc.

• ​Use a combination of small, capital alphabets, special characters.

• Make a lengthy password with at least 8-16 characters

• Change passwords periodically

• Use different password for different websites​

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Computer Virus

• UA malicious computer code that is designed with some negative intent like deleting files, stealing information, slowing down the computer etc.

• ​Antivirus software protect the computer from a virus infection.

• Scan the files in background for any malicious code.

• Scan any incoming and outgoing traffic on a network

• ​Comparing a file with a database of known virus codes.

• Heuristic checking to look for a suspicious behavior and finding a virus code that is not in the database.​

• Quarantine the suspected file and let the user decide the action. Sometimes there is a false alarm for a normal file

Computer Virus

• UA malicious computer code that is designed with some negative intent like deleting files, stealing information, slowing down the computer etc.

• ​Antivirus software protect the computer from a virus infection.

• Scan the files in background for any malicious code.

• Scan any incoming and outgoing traffic on a network

• ​Comparing a file with a database of known virus codes.

• Heuristic checking to look for a suspicious behavior and finding a virus code that is not in the database.​

• Quarantine the suspected file and let the user decide the action. Sometimes there is a false alarm for a normal file.

Data Protection Acts

• used fairly, lawfully and transparently

• used for specified, explicit purposes

• used in a way that is adequate, relevant and limited to only what is necessary

• accurate and, where necessary, kept up to date

• kept for no longer than is necessary

• handled in a way that ensures appropriate security, including protection against unlawful or unauthorised processing, access, loss, destruction or damage

Data Protection Rights

• be informed about how your data is being used

• access personal data

• have incorrect data updated

• have data erased

• stop or restrict the processing of your data

• data portability (allowing you to get and reuse your data for different services)

• object to how your data is processed in certain circumstances