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Unit 650 Periods Allocated

Data Communication and Networking

Covers data transmission media, IP addressing, subnetting calculations, routing, and reference models.

Syllabus Competency Mappings

Level 6.7Competency Level

Explores how multiple networks are interconnected to form the Internet.

Key Topics:
  • IPv4 addresses
  • Subnetting and Subnet Masks
  • CIDR notation
  • IPv6 overview
Level 6.10Competency Level

Investigates the role of reference models to describe the network architecture.

Key Topics:
  • OSI 7-layer reference model
  • TCP/IP 4-layer model
  • Data flow in network layers

A/L ICT Competency Study Guide

1. IPv4 Addressing & Subnetting

An IPv4 address is a 32-bit binary number, represented in dotted-decimal format (e.g., 192.168.1.1). Subnetting splits a large network block into smaller, manageable subnets.

Subnet Calculation Example:

Given the network address 192.168.1.0/26:

  • The /26 CIDR notation represents 26 network bits. The remaining 32 - 26 = 6 bits are host bits.
  • Subnet Mask: 26 consecutive 1s in binary is 11111111.11111111.11111111.11000000, which translates to 255.255.255.192.
  • Total Hosts: 26 = 64 hosts per subnet.
  • Usable Hosts: 26 - 2 = 62 (subtracting the Network ID and the Broadcast Address).
PropertyBinary ValueDecimal Value
Network ID192.168.1.00000000192.168.1.0
First Usable Host192.168.1.00000001192.168.1.1
Last Usable Host192.168.1.00111110192.168.1.62
Broadcast Address192.168.1.00111111192.168.1.63

2. OSI 7-Layer Reference Model

The Open Systems Interconnection (OSI) model standardizes network communication functions across 7 layers:

  1. Application: Interface for end-user network services (HTTP, FTP, SMTP).
  2. Presentation: Handles data formatting, translation, and encryption (SSL/TLS).
  3. Session: Manages, maintains, and terminates connections between applications.
  4. Transport: Coordinates reliable end-to-end data delivery (TCP, UDP, ports).
  5. Network: Determines routing path using logical IP addresses (Routers, IP).
  6. Data Link: Manages physical node-to-node framing and error detection (MAC, Switches).
  7. Physical: Transmits raw binary bits over cable/wireless media (Cables, Hubs).

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