Computer Science Topic 3 - Networks

LAN

(Local Area Network) A network inside one organization or one building traditionally made of wires and hubs connecting servers and clients. Typically in a business, connecting employees' PCs to the company's servers.

WAN

(Wide Area Network) A series of LAN or VLAN or WLAN that are connected. An example would be the internet.

VLAN

(Virtual Local Area Network) LANs that are connected make up the VLAN. Different buildings or departments within one building could all have their own network but then also have access to the networks in other departments. The VLAN connects them and lets this happen.

WLAN

(Wireless Local Area Network) Less secure, but more convenient, than the LAN. Wireless routers allow people physically close to the building to access the network, even if they're not part of the organization. This is the security threat. But WLAN does not require users to connect with cables, and they can use local wi-fi instead (however, this is slower than the ethernet cables).

SAN

(storage area network) A network containing large amounts of storage (HDD). Usually virtualized so users don't need to worry about the actual machines containing the storage devices - commonly "data centers". An example is the cloud.

VPN

(Virtual Private Network) Clients who are not in a LAN can connect to it. It can improve security of a LAN while still letting the clients have access to some information. They commonly obtain an IP address from a LAN by connecting to it, faking the client's location.

PAN

(Personal Area Network) Used to connect devices belonging to one user, or maybe a family. Typically running through a wireless router in a home.

P2P

(peer-to-peer) Each computer is a node in a network and the nodes share information with each other. This is more reliable because there is no central server, all computers on the network would have to be unavailable for the network to stop working. Resources are also made more available and allows for easy backup files.

Ethernet

A standard for LAN connections. This includes a communication protocol, as well as a standard type of connection card and standard cables.

OSI

(Open System Interconnection) By establishing STANDARD layers with specific responsibilities, it's possible to implement communication (networking) with interchangeable modules. The layers are:

• Application: does various services for the applications used by the end-users.

• Presentation: provides the data formatted information, data compressed information, and data encryption information to the application.

• Session: manages the sessions between the two users.

• Transport: encodes, packets, transmits, and decodes the information.

• Network: Routes packers through an intermediary device.

• Data link: error handling of physical transmission.

• Physical: transmit bits of media between devices and defines the voltage levels and media specs.

Technologies Required for VPN

• Two fundamental VPN technologies are encryption and tunneling. Tunneling is when you establish and maintain a logical network connection. On the network the information is encapsulated then de-encapsulated on the receiving side after being transmitted.

• Basically they need: A LAN connected to the internet, a computer outside the LAN also on the internet, and a VPN client and server running on a lone machine and the original LAN.

Evaluation of use of VPNs

Provides mobility and security. People can work from home but still be secure. Overall good.

Protocol

A common, agreed-upon, computer language that all computers need to be able to understand, to allow for communication between systems.

Data Packet

Small groups of data that contain encoded data with information about the destination and sender. They can travel through networks wirelessly or through cables.

HTTP

(HyperText Transfer Protocol) Sends and receives webpages.

FTP

(File Transfer Protocol) Downloads, uploads, and transfers files

SMTP

(Simple Mail Transfer Protocol) Used by email servers to send emails from one to another

Data Integrity

The overall completeness, accuracy, and consistency of data.

Why are protocols needed?

Without them no information can be transmitted because computers won't know how to interpret the signals.

Flow control

what ensures that the rate at which a sender is sending is in proportion to the receiver's receiving capabilities. Needed so that a computer never overwhelms the other, and ensures it can keep up.

Deadlock

two nodes or processors are trying to access the same node at the same time, stopping both of them from proceeding. The protocol then requeues them so that traffic can properly flow.

Congestion control

congestion is when a node or link carries so much data that it deteriorates network service quality which causes delays, can lead to data packet loss, and can block new connections. Congestion control stops that.

Error checking

Techniques used to detect noise or other impairments that are introduced to data while it is transmitted. Error checking uses checksums.

Explain why the speed of data transmission across a network can vary

• Connection speed averages: can differ. For dedicated LAN connections it can be anywhere from 10-150Mbps, it depends on cable or wireless (wifi). For broadband WAN connections it can be anywhere from 1-100Mbps. This includes 4G.

• Traffic: the more network traffic the slower the data will transfer, and traffic can vary from time to time. **THIS ONE IS KEY

• Time of day: as more people get on to download traffic increases.

• Distance: the farther you are the longer it will take.

• Infrastructure: if the infrastructure is up to date, organized, and well kept it will function better.

• Two minor causes can be environment issues (temperature, etc) and type of data being transmitted.

Explain why compression of data is often necessary when transmitting across a network.

• The smaller data is, the more can be sent during the same amount of time, allowing the computers to be more efficient.

• It makes less data transmission.

• It will take up less space when it finally gets to its destination.

• Compressing also helps data to backup, transfer files over the web, and helps to encrypt, in a faster and easier way.

Copper wiring

(metal) Security: okay if encrypted. Speed: 100Mbps-1Gbps Cost: less than one euro per meter. Reliability: susceptible to electromagnetic interference.

Fiber-optic

(glass) Security: very secure. Speed: 5-100Gbps. Cost: 2-8 euros per meter. Reliability: fragile.

good distance

Radio waves (WLAN/wifi)

Security: very insecure unless encrypted. Speed: 5-100Mbps Cost: technically free Reliability: susceptible to interference.

Wired transmission

• Copper

• Fiber-optic cable

Wireless transmission

• Radio wave

• Microwave

• Infrared

Outline advantages that make Optical Fiber better than Copper Cables for outdoor use.

• Optical fiber provides a much farther bandwidth than the copper cables.

• Optical fiber can carry more information than copper cable.

• Copper cable is also less secure, and can be affected by electromagnetic interference.

• This means if you use optical fiber you can use it over a bigger space outdoors with less effort, and that it will carry more of the information you need, making it the better choice.

Explain how data is transmitted by packet switching (connectionless socket operation).

• Uses User Datagram Protocol (UDP). The datagram is a self-contained unit with all the information that is needed to deliver information. Like a letter with a stamp and address on the outside, and the information on the inside.

• Breaks the data down into the packets then sends it through the network by using devices to transfer it. The devices then route it to the desired destination, where that device reassembles it.

• A socket doing this does not have to connect to the destination socket, it can just send the datagram. UDP then tries as hard as it can to deliver. It is faster and more efficient than connection-oriented sockets, but it is not guaranteed.

Importance of checksums

• It helps to validate the data being received and check if there was an error in transmission.

• With the data, the sender also uses an algorithm to calculate the checksum of the data and sends it. When the receiver gets the data, they can calculate the checksum of that using the same algorithm. If they match, the transmission is error free.

• The checksum is the binary code added together.

• In a system that can lose information fairly easily the checksum is vital towards knowing whether or not the data you receive is accurate.

Advantages of wireless networks

• Uses unlicensed radio spectrums, so it doesn't cost anything.

• They can be set up without cables, so not cable cost, time to lay cables, or space needed for the cables.

• Wifi supports roaming between different routers. They can switch from router to router depending on the best connection.

• It has global standards.

• Setup costs are minimal. Many different types of networks are available and affordable.

• Public access to the internet is wide-spread.

Disadvantages of wireless networks

• It can get interference as the 2.4GHz spectrum often has many other devices on it.

• It has limited range.

• WEP, an encryption that is not difficult to hack. Weaker security.

• Access points can be used to steal data.

• It is slower.

• Higher error and disconnection rates.

• High rates of addiction.

• High rates of driving accidents.

• Higher rates of cancer HYPOTHESIZED

• More eye care problems HYPOTHESIZED

Hardware of Wireless Networks

• Nodes: PC, laptops, tablets, printers, etc.

• Wireless network interface cards (enables wifi communication between the device and the network).

• Radio waves (bluetooth/wifi)

• A connection point like a wireless AP or a router.

Software of Wireless Networks

• A network operating system (with drivers).

• A protocol stack (TCP or IP).

• Applications, a browser or file explorer.

wifi characteristics

• used in laptops or mobile devices to wirelessly connect to the network.

• The preferred network type for home networks.

• Relatively slow to fast data transmission, depending on the version.

• Backwards compatible with most older wifi standards.

• Small transmitting radius, one of the reasons it is suited for homes. Usually less than 20 meters.

WiMAX characteristics

• For large distance high speed internet access.

• Relatively cheap method for providing internet over a large area. Used for poorer countries.

• Can be used as a wireless variant of DSL phone transmission lines.

• Like 4G but 50% slower. It is not compatible with 3G but is with 4G.

3G (third generation) characteristics

• The primary way for mobile phones to access the internet.

• Allows to tunnel the phone lines (phones don't have to switch back to the phone network).

• Relatively fast.

4G

• Current generation.

• Digital telecommunication standard reaches up to 100Mb/s.

• Uses LTE which can reach up to 300Mb/s, is the most widely used wireless technology.

Authentication

• One factor is something you know like a password.

• Two factor is something you have, like a security card or ID.

• Three factor is something you are, like a fingerprint.

Firewalls

• They can be hardware, software, or a hybrid.

• They control the incoming and outgoing network traffic.

• They analyze data packets based off predetermined rules.

MAC Address (Media Access Control Address)

• Hard-coded into devices by the manufacturers.

• Managed by the IEEE (institute of electrical and electronics engineers).

• Used to identify specific pieces of hardware.

Encryption - UserID

A username and password.

PSK

(pre shared key) Unique pre-shared keys. Kind of like the tokens in github being used to log into android studios.

WEP

Wireless equivalent privacy, a very simple algorithm. People broke it quickly and it has not been used since 2004. In 2003 WPA replaced it.

WPA/WPA2

(wifi protected access)

• WPA, 2004-2006, intrusions can be made from outside the network.

• WPA2, from 2006 to now. Intrusions can only come from someone who already has access to the network.

UserID - Advantages & Disadvantages

Advantages:

• User groups can be created to help manage the user rights in batches.

• Each user can set their own access rights.

Disadvantages:

• Can be stolen.

• System can be bypassed.

• Cannot protect against intercepting messages in the network.

Encryptions - Advantages & Disadvantages

Advantages:

• Hard to break when strong.

• Computers are Fast enough to encrypt while doing a task.

Disadvantages:

• Users often make passwords that are easy to guess.

• Passwords have to be transmitted over the network so the receiver can read the message.

• Some encryptions are built to have backdoors.

• Can be complicated

Software Firewall - Advantages & Disadvantages

Advantages:

• Monitors and controls the traffic between computers and networks to prevent unauthorized device access.

Disadvantages:

• Can slow down the device.

MAC Address - Advantages & Disadvantages

Advantages:

• Extra security because it has a whitelist of allowed devices. Each device has a unique MAC address found on a Network Interface Card.

Disadvantages:

• List can easily be found with appropriate software.

• The list can be hard to manage.

WEP - Advantages & Disadvantages

Advantages:

• Worked with the legacy systems.

Disadvantages:

• Outdated, not secure.

WPA/WPA2 - Advantages & Disadvantages

Advantages:

• The best/most recommended option.

Hardware Firewall - Advantages & Disadvantages

Advantages:

• Prevents attackers from accessing the network over the internet.

Disadvantages:

• Physical proximity will allow access to network.

Explain why other standards like ASCII, UNICODE, and HTML are still needed, even though they are not part of the OSI standard.

They help to provide many different ways for the computers to standardize their information. They help different types of computers standardize the information in ways that work best for them.

TCP

(Transmission control protocol) Makes sure data packets are received and sequenced right.

IP

(Internet Protocol) Makes sure data sent across a network goes to the right person.

Computer Network

A group of computer systems or other hardware devices that are linked through communication channels. This allows for communication and research-sharing.

Server

A software application that provides some kind of service to other computers connected to the same network.

Client

The software application or computer system that requests a service from a server on the same network.

Switch

Something that can identify which devices are connected to a port. If a device wants to send data to a specific port the switch transmits it to the device connected to said port.

Node

A redistribution point or an end communications point.

Internet

A network of networks connected using IP (internet protocol). It powers large ranges of communication media like World-Wide Web (documents connected by hyperlinks), emails, chats, etc. Hosts on the internet are connected through publicly accessible communications media like the phone system.

Intranet

Private internet. Made of web pages and viewed through a browser, access is restricted to users within an organization. Usually hosted on a machine in the building.

Extranet

A controlled private network that allows partners, vendors, suppliers, etc, to gain access without granting access to the organization's entire network. Often restricted through IDs and passwords.

Bandwidth

The maximum amount of data that can pass from one point to another in a unit of time.

Lossless Compression

It compresses the file and does not lose data, it recreates the original file. Usually used in places where the data would be missed such as documents.

Lossy compression

Some data can be lost and the original file can never be recreated. Lossy has higher compression rates. It makes an approximation of the original data. Usually used in videos, sound, or images, where the loss would not be noticed.

Necessary components to create a public wireless network

• Router

• modem

• wireless receiver

• NICs

• wireless access point

• computer

• cabling

Router

A device that forwards data packets to the appropriate part of the network