Network Fundamentals & Data Transmission

• Topic is networks

Network Fundamentals

• Networks include local area network (LAN), virtual local area network (VLAN), wide area network (WAN), storage area network (SAN), wireless local area network (WLAN), internet, extranet, virtual private network (VPN), personal area network (PAN), and peer-to-peer (P2P).
• Standards enable compatibility through a common "language" internationally.
• Communication over networks is broken down into different layers
• Awareness of the OSI seven layer model is required
• Understanding the functioning of each layer is not needed
• The use of a virtual private network has led to changes in working patterns
• Globalization has been accelerated by the technical advances linked to network development

Data Transmission

• Protocols ensure data integrity, flow control, prevent deadlocks and congestion, and provide error checking
• The speed of data transmission across a network can vary
• Compression has enabled information to be disseminated more rapidly due to compression reducing transmission times
• Transmission media characteristics include speed, reliability, cost, and security
• Transmission media options include metal conductor, fiber optic, and wireless
• Data is transmitted by packet switching

Network Types and Devices

LAN (Local Area Network)

• Network of nodes are connected through a central network device or server
• Limited to one geographical location without connections to other outer networks
• Switches and hubs connect devices
• Switches have tables to direct packets to the correct port
• Used for communication within small offices

VLAN (Virtual Local Area Network)

• Logically groups workstations, servers, and network devices
• Appear on the same LAN despite geographical distribution
• VLANs improve network performance
• Network administrators manage permissions and security for node groups with different permission level
• These groups are not physically linked to the same router/switch but form logical groups
• Examples are teachers and admins on different VLANs in a school network

SAN (Storage Area Network)

• Network of storage disks that are block level storage for servers
• Used to store data and maintain backups

WAN (Wide Area Network)

• Connects multiple LANs
• Distributed across different geographical locations
• Used in larger areas like schools, offices, and hospitals
• Routers and digital subscriber lines are needed to construct WANs

VPN (Virtual Private Network)

• Company's private network using an internet connection to connect remote sites or employees
• Access requires secure login.
• Masks IP addresses and locations
• Secures privacy through tunneling
• Data security is ensured through encryption
• Applications, routers, and encryption protocols like SSL and TLS are needed

PAN (Personal Area Network)

• Connects devices or peripherals directly to a device
• Examples are printers, external hard drives, and Bluetooth devices connected

P2P (Peer-to-Peer Network)

• Devices connect without a central server
• It is easy to implement, requiring only wired or wireless NIC cards
• Central management is not present
• Purpose is to share resources like printers and storage

WLAN (Wireless Local Area Network)

• Allows devices to connect and communicate wirelessly
• Unlike LAN, communication is over Wi-Fi versus Ethernet cables
• Wireless access points and integrated routers are used to construct WLANs
• Devices connect via a pass key

Intranet vs. Extranet

• Intranet is a private network for secure collaboration and communication among a company’s employees, used to store crucial information
• Extranet is similar to the intranet, it's a private network within an organization
• Extranets use the internet to connect to entities outside the network such as suppliers and customers
• It provides a real-time platform for collaboration with external parties and streamlines processes

Standards in Networks

• Standards enable the construction of networks using different devices from different manufacturers
• They also enable communication between devices from different locations

Hardware Standards

• Computer networks use equipment from various vendors, that must work together
• This is achieved through standardized manufacturing procedures
• Ports, Ethernet cables, and wireless standards are consistent across devices

Software and Protocols

• Networks also follow standard communication protocols
• Protocols create rules for network communication, including packet formatting, type, size, and error handling
• Protocols work in layers, from the user interface to the physical connection, with each layer following specific rules

OSI Layers

• Application Layer: Provides human-computer interaction where applications can access network services
• Presentation Layer: Ensures data is in a usable format and handles data encryption
• Session Layer: Maintains connections and controls ports and sessions
• Transport Layer: Transmits data using transmission protocols including TCP and UDP
• Network Layer: Decides which physical path the data will take
• Data Link Layer: Defines the format of data on the network
• Physical Layer: Transmits raw bit streams over the physical medium

TCP/IP Stack

Sender Side

• Application Layer: selects protocol related to app sending message (HTTPS, SMTP)
• Transport Layer: establishes end-to-end connection with recipient, splits data into numbered packets, and requests lost packets to acknowledge receipt
• Network Layer: adds receiver and destination IP addresses
• Link Layer: establishes connection by adding MAC addresses of sender and destination on each hop

Destination Side

• Link Layer: removes MAC addresses
• Network Layer: removes IP addresses
• Transport Layer: uses port number to decide what application to send the packet to
• It reassembles all the packets in the correct order
• Application Layer: data is received by the correct app from the transport layer

Virtual Private Networks (VPNs)

Features

• Use a company's private network over the internet to connect remote sites or employees via a secure login
• Masks IP addresses and locations
• Secures privacy through VPN tunneling
• Data security is ensured through encryption

Technologies Used To Establish VPN

• VPN client and server with communications
• Encryption protocols such as SSL 3.0, TLS, and IPSec are used for secure data transmission

Authentication

• It is a vital part of VPNs, requiring more than just usernames and passwords
• Stronger methods use certificates, one-time passwords, and software tokens

Tunnelling

• It is implemented using software. The one creates a secure tunnel between a user's device and the VPN server
• It hides the user's real IP address by adopting the server's IP

Security and Use

• Allows working from home or other countries
• Helps to hire experts from other countries
• Data is encrypted, preventing interception
• Reduces day-to-day office costs
• Companies can hire staff from different time zones, which impacts overall business and productivity

Compression

• Involves restructuring files using compression algorithms to reduce storage space and transmission time
• Lossy and lossless compression techniques are used
• Different compression algorithms support text, images, and sound files
• Compression reduces both file size and bandwidth needed for transmission
• Lossy compression discards data, which may be unacceptable for audio and video files

Factors Impacting Network Speed

• Malicious software, spyware, malware, and viruses can attack the system
• Wired, wireless, mobile, broadband, fixed wireless, satellite, and cable represent different connection types
• Hardware malfunction such as modem or router configuration issues are a factor
• External factors include network traffic volume

Wireless Networking: Advantages and Disadvantages

• Wireless networks have changed working patterns, social activities, and raised health issues
• They enable connectivity between different locations

Advantages

• Connected devices are able to move around the coverage area
• Eliminates the need for cables, reduces costs, and saves time
• Provides automatic switching between routers based on connection quality
• Requires minimal setup costs

Disadvantages

• Offers a higher chance of interference compared to wired networks
• Uses limited range
• It can be hacked with WEP encryption
• Access points can be used to steal data
• Network speed compromised when more devices are connected

Reliability

• Reliability depends on the strength of the wireless signal, distance from the router and topology of surrounding area
• Slower data transfer speeds apply
• Ethernet is more reliable as the signal doesn't depend on distance from a router, and wires support longer distances
• Ethernet is also immune to interference
• With ethernet, topology is not an issue but reliability is affected if it is cut

Devices for Wireless Networks

• Access point/repeater connects wireless devices to a network and strengthens the signa
• Wireless/wired NIC (network interface card) facilitates connections
• Embedded antenna in wireless cards allow them to connect wirelessly
• Routers forward data by inspecting packets' destination addresses
• Router's ensure secure and reliable packet delivery

Wireless Network Security Methods

Authentication and access permissions

• Proving identity access to data and using passwords and biometrics are possible
• Permissions for accessing files/resources should be specified

Encryption protocols

• Data is encrypted using an encryption key
• The key is transmitted in an encrypted state and decrypted at the receiver

MAC Media Access Lists

• Checks MAC addresses against a list of authorized devices
• Denies network access to unauthorized devices.
• Prevents unauthorized access, and adds an extra authentication layer

Protection Against Unauthorized Access

• Prevent with no access without usernames/passwords, which should be regularly changed and made difficult to guess.
• Decrypted data should be allowed to be accessed only when user has the decryption code.
• User (User should be of the context of the questions) should be trained for safe practices; to create a risk-conscious /security-aware culture within the organisation
• By installing virus checkers/spyware software, prevent damage to data files or the system / to prevent data being extracted from the files/system.
• Physical security measures should be in place

Firewall

• Blocks and allows traffic from specific IP addresses
• Blocks and allows certain types of packet; examples are pings/echo requests
• Maintains information about current connections and only allows packets relevant to these connections through.
• Acts as a proxy server, stops computers on the Internet directly accessing devices on the LAN;
• Identifies unusual behavior from a host; for example, sending an unusually large amount of data.
• Rules are written to specify conditions under which to block/allow.

Types of Wireless Networks

• WiFi: Small radius, for example at home
• WiMAX: Long distance and cheap
• 3G and 4G: Mobile networks, allow tunneling