Understanding Computer Networks: Protocols, Types, and Security

Computer Networks

Internet Protocols & Hardware

Internet communication relies on a set of rules and protocols, similar to how humans communicate. Internet hardware enables the connection.

• Examples: TCP, Ethernet, Handshaking, UDP, FTP, HTTP, Telnet, SSH. Network hubs, switches, routers, and dedicated cabling are examples of network hardware.
• Applications: Internet protocols are applied to network hardware to enhance security.

Network Types

LANs – Local Area Network

A LAN serves a local area, typically within a building or a group of buildings in a geographical area. Common LAN topologies include:

• Ring Networks: Each computer connects to its neighbors, transmitting data around the network. It performs well under heavy traffic but can crash if a connection fails.
• Bus Networks: Each device connects to a common spine. It is resilient to individual device failures but can be difficult to troubleshoot if the entire network fails.
• Star Networks: Each device connects to a central hub or switch. It is resilient to individual device failures, but the entire network crashes if the central hub fails.
• Hybrid/Tree Networks: Star networks connected to a common bus backbone. It combines the advantages of star and bus networks but can be difficult to wire.

Intranet

An intranet is a private network providing services similar to the internet, such as email, messaging, and web pages, but only for internal users. Businesses often use intranets for:

• Viewing internal web pages (e.g., company calendars)
• Internal email and instant messaging
• Sharing internal documents

WLANs – Wireless Local Area Connection

A WLAN behaves like a LAN but uses radio waves or infrared signals instead of wires. Security is a concern.

• Devices: Wi-Fi (wireless fidelity) enables network connections using radio waves.
• Laptops are optional but desirable for mobility.
• Wireless network interface controllers (WNICs) transmit data via radio waves.
• Wireless routers have antennas and lack cables.
• Wireless access points (WAPs) connect wireless devices to wired networks.
• Other devices include mobile phones, printers, PDAs, and portable media players.
• Data transmission methods include spread spectrum radio waves and infrared signals.

WPANs – Wireless Personal Area Network

A WPAN is a small network used by one person, typically using Bluetooth for functions like transferring photos.

MANs – Metropolitan Area Network

A MAN is similar to a LAN but covers a larger area, often owned by a consortium of users, extending across a city.

WANs – Wide Area Network

A WAN connects multiple LANs through routers or modems, covering a large geographical area.

• Modems convert digital data to analog for transmission through telephone lines.
• HTTP proxy servers act as buffers between WANs (like the internet) and LANs.
• The internet is a global WAN accessible to anyone.
• Extranets extend an organization’s intranet to selected external users.
• Email is the primary means of communication over the internet.
• Businesses use WANs to connect LANs and access the internet.
• VPNs use the internet or other WANs to transmit data, not a physically private network.
• Videoconferencing enables communication between different locations.
• Other applications include telephone call centers and online banking/shopping systems.

Network Security

Network security includes physical and software measures.

Physical Security

Procedures to prevent physical access to computers or server rooms.

• Securing computer rooms: Prevents unauthorized access to data.
• Security guards: Provided by security firms to protect computer facilities.

Software Security

Protects against intrusions into networked computer systems.

• Firewalls: Prevent unauthorized access, available in hardware or software forms.
• Encryption: Converts data into a code by scrambling or encoding it.
• Digital certification: Issued by trusted certificate authorities.
• Authentication techniques: User IDs and passwords to identify users.
• Anti-Virus: Removes viruses, Trojan horses, and worms.
• Chip and PIN cards: Used for logging on by inserting the card and entering a PIN.
• Anti-spam: Rejects unwanted emails.
• Anti-pop-up software: Blocks pop-up messages.
• Anti-spyware software: Prevents unauthorized access and control of computers.
• Wired equivalent privacy (WEP): Code for WLAN access.
• Wi-Fi protected access (WPA): Enhanced encryption over WEP with longer keys.

Electronic Conferencing

Hardware

Telephones, webcams, microphones, speakers.

Types of Software

• Conference software: Compresses audio and video into data packets for network transmission using codecs.
• VOIP software: Enables phone conversations over the internet.
• Instant messaging: Real-time text message exchange over the internet.

Uses

• Businesses: Videoconferencing saves money and time, but some employees find it time-consuming. It is used for quick meetings with low assistance. Phone conferencing and instant messaging are less common.
• Schools: Videoconferencing connects students from different countries, promoting cultural understanding. Phone conferencing helps disabled students. Instant messaging is common among teenagers but not used in schools.
• Research meetings: Videoconferencing is used for small classes with limited discussion. Telephone conferencing helps researchers stay in touch with supervisors.

Types

Videoconferencing

Advantages: No travel time or costs, immediate meetings, environmentally friendly.

Disadvantages: No direct eye contact, low video/audio quality, power cuts can interrupt.

Phone conferencing

Advantages: Lower cost, simple equipment, good sound quality, no need to worry about appearance.

Disadvantages: No facial expressions, documents cannot be seen, limited participants.

Instant messaging

Advantages: Instantaneous, cheap, saves time and money for businesses.

Disadvantages: Can distract teenagers, risky due to unknown contacts and virus spread.