OCR J277 Topic 1.3

Networks, Hardware & Protocols

Mastering Topologies, The Cloud, DNS, and Essential Hardware.

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1

Star vs. Mesh Topologies

Exam Trap: The Drawing Rule

When asked to draw a Star Topology, never connect computers directly to each other. All lines must go to the central Switch.

Star Topology

All devices connect to a central Switch.

Easy to add new devices.
Fewer collisions than bus.
Single Point of Failure: The Switch.

Mesh Topology

Every device connects to others. No central switch.

Self-Healing: Routes around damage.
Very Expensive: High cabling cost.

Key Vocabulary

Topology: The physical layout or arrangement of the computers and cables in a network.
Collision: When two pieces of data try to travel down the same cable at the same time and crash.
Self-Healing: If one cable breaks, the data can find a different route to get to its destination.
Switch: A smart device that connects computers together and directs data only to the correct person.
2

Essential Hardware

You must know the specific job of these 5 components. Don't mix them up!

NIC (Network Interface Card)

Internal hardware required to connect a device to a network. Contains the unique MAC Address.

Switch

Connects devices on a LAN. Intelligent: Reads the MAC address and sends data only to the intended recipient.

Router

Connects different networks together (e.g., joins your Home LAN to the Internet/WAN). Routes data packets across the internet.

WAP (Wireless Access Point)

Hardware that converts data from a wired cable into a wireless signal (radio waves) for Wi-Fi devices.

Transmission Media

Wired (Ethernet/Fibre): Uses Copper cables or light (Fibre Optic). Fast & Reliable.
Wireless: Uses Radio Waves. Flexible but subject to interference.

Key Vocabulary

LAN (Local Area Network): A network covering a small geographical area, like a single building or school.
WAN (Wide Area Network): A network covering a large geographical area (like the Internet).
Packet: A small chunk of data. Files are chopped into packets to be sent over the internet.
MAC Address: A unique serial number burned into the chip of a network card. It cannot be changed.
3

Protocols & The Internet (DNS)

How a URL becomes a Website

The Domain Name System (DNS) translates human-friendly URLs (google.com) into computer-friendly IP Addresses (142.250.180.14).

1

Request

Browser asks the DNS Server for the IP of a website.

2

Lookup

DNS checks its database. If found, it gets the IP.

3

Return

DNS sends the IP Address back to the browser.

4

Connect

Browser uses the IP to connect to the Web Server.

Key Vocabulary

IP Address: A set of numbers (e.g., 192.168.1.1) that identifies where a computer is located on a network.
URL: The text address of a website (e.g., www.bbc.co.uk) that is easy for humans to remember.
Database: An organised collection of data. The DNS server uses one to store URLs and IP addresses.
4

Network Performance

Bandwidth Splitting

Bandwidth is shared. If 1 user downloads a file, they get full speed. If 10 users download, they split the speed. More users = Slower network.

Interference Factors

  • Physical Walls: Thick concrete blocks Wi-Fi signals.
  • Electronic Interference: Microwaves and cordless phones use 2.4GHz frequency, causing dropouts.
  • Distance: Further from the WAP = weaker signal.

Key Vocabulary

Bandwidth: The maximum amount of data that can be sent across a network at once.
Interference: When signals (like radio waves) are disrupted or blocked by walls or other electronic devices.
Frequency: The channel that wireless devices use to communicate (e.g., 2.4GHz).
5

Network Models

Client-Server

Central Server controls security and backups.

  • Central Backups: Data safe if PC breaks.
  • Central Security: Admin manages antivirus.
  • Expensive: Needs specialist staff.

Peer-to-Peer (P2P)

No central boss. All computers equal.

  • Cheap: No server hardware needed.
  • Easy Setup: Just plug in.
  • Insecure: Users manage own security.

Key Vocabulary

Peer: An equal. In P2P, all computers have equal status and rights.
Centralised: Controlled by one main point (the Server).
Backup: A copy of files kept in a separate location in case the original is lost or damaged.
6

The Cloud

Definition: "The Cloud" refers to remote servers that store data and software, which you access over the Internet (e.g., Google Drive, Netflix, Dropbox).

You don't own the hardware; you pay a third party to host it for you.

Advantages

  • Access Anywhere: Files can be accessed from any device with internet.
  • Automatic Backups: The host company handles backups for you.
  • Scalable: Need more storage? Just pay for an upgrade instantly.

Disadvantages

  • Needs Internet: No connection = No files.
  • Security Risks: You are trusting a 3rd party with your sensitive data.
  • Subscription Cost: Monthly fees can become expensive over time.

Key Vocabulary

Remote: Located far away (not in the same building as you).
Third-Party: An outside company that provides a service (e.g., Google or Dropbox).
Scalable: The ability to easily increase size or capacity (e.g., adding more storage space instantly).
7

Web Servers & Clients

The Internet works because computers have specific roles. You must be able to define what a "Client" is in an exam context.

The Client

"The Requestor"

A client is a device or software that requests data or services from a server.

Example: Your Web Browser (Chrome/Edge) is a client that requests webpages.

The Server

"The Provider"

A server is a powerful computer that provides services or data to clients.

Example: A Web Server holds website files and sends them to the client when asked.

Lesson Summary & Review