LAN & WAN (OCR A-Level Computer Science): Revision Notes

LAN & WAN

Overview

Local Area Networks (LANs) and Wide Area Networks (WANs) are two fundamental types of networks that connect devices and allow data communication. LANs and WANs are defined by their size, purpose, and the technologies they use. Understanding these terms is essential for grasping how networks are organised and managed, whether within a single building or across continents.

Local Area Network (LAN)

• Definition: A LAN is a network that covers a small geographical area, like a single building, office, or school. LANs are used to connect devices within proximity, typically within a few kilometres at most.
• Characteristics:
  • Limited Range: LANs usually cover a single building or campus.
  • High Speed: LANs often provide high data transfer rates (usually between 100 Mbps and 1 Gbps).
  • Ownership: LANs are usually owned, managed, and maintained by a single organisation.
  • Connection Medium: LANs often use Ethernet cables or Wi-Fi for connectivity.
• Examples:
  • A school's computer network that links classrooms and administrative offices.
  • A corporate office network that connects employee workstations, printers, and servers.

Wide Area Network (WAN)

• Definition: A WAN is a network that spans a large geographical area, potentially covering multiple cities, countries, or even continents. WANs connect multiple LANs and allow them to communicate with each other.
• Characteristics:
  • Wide Range: WANs cover large distances and often involve connecting different regions or countries.
  • Lower Speeds: WANs generally have slower speeds than LANs due to the long distances and multiple connections involved (usually from 1.5 Mbps to 200 Mbps, though speeds can vary).
  • Shared Ownership: WANs are often maintained by multiple organisations or service providers. For example, the internet, the largest WAN, is a collection of networks managed by various entities.
  • Connection Medium: WANs use a mix of media, including fibre-optic cables, leased phone lines, satellite links, and wireless technologies.
• Examples:
  • A corporation with offices worldwide uses a WAN to connect its regional LANs.
  • The internet is considered the largest WAN, connecting networks and devices globally.

Key Differences Between LAN and WAN

Feature	LAN	WAN
Geographical Area	Small (single building or campus)	Large (spanning cities, countries, or continents)
Speed	Generally high (100 Mbps to 1 Gbps)	Generally lower than LAN speeds (varies widely)
Ownership	Single organisation	Shared ownership by multiple entities
Connection Type	Ethernet cables, Wi-Fi	Fiber-optic, leased lines, satellite, etc.
Cost	Lower (limited to local setup)	Higher (infrastructure for long distances)

Network Devices Used in LANs and WANs

LAN Devices:

• Switches: Connect devices within a LAN and enable efficient data transmission.
• Routers: Direct data between different networks, often connecting a LAN to a WAN (such as the internet).
• Access Points: Allow wireless devices to connect to a LAN via Wi-Fi.

WAN Devices:

• Routers: Connect different LANs and direct data across a WAN.
• Modems: Convert digital data for transmission over long distances through phone lines or cable systems.
• Satellite Dishes and Antennas: Used for wireless transmission over very large distances in some WANs.

Examples

LAN Example:

• A university campus network where computers in classrooms, libraries, and administrative offices are connected, allows students and staff to access shared resources like printers and servers.

WAN Example:

• A bank with branches in multiple cities connects its branches via a WAN, allowing it to securely access central financial systems and customer data.

Note Summary