Computer Networks (Components and Types)

Context: FIT1047_MOC · the networks half begins (LO5–6) · vocabulary + the one calculation that recurs: transfer time from data size ÷ rate

Quick Revision

• 🎯 Objective: four components ➔ client (user access) · server (stores data/software for clients) · switch (connects computers within a LAN) · router (connects two or more networks).
• ⚡ Key Constraint: transfer-time arithmetic — mind GByte vs Gbit ($\times 8$) and the unit ladder M→G→T.

📝 Core

• Network types by reach ➔ LAN (room/building; clients+servers sharing a circuit) → BN backbone (< few km; high-speed LAN interconnect) → MAN (> few km, across locations) → WAN (same idea, longer distances).
• The Internet ➔ a network of networks — millions of networks, billions of devices, glued by one standard protocol set (Internet Model (Layers, Protocols, Encapsulation)).
• Key metric ➔ data transmission rate in bits/second: ~1 Mbps home upload · 50–500 Mbps WLAN · 1 Gbps LAN · 10 Gbps backbone · Tbps optical fibre.

📊 Applied Exercise — lecture calculation (50 GB movie)

$$\begin{array}{rl}50\text{ GByte}& =400\text{ Gbit}=400000\text{ Mbit}\\ \text{ADSL }1\text{ Mbps}& :400000\text{ s}\approx 4\text{ d }15\text{ h}\\ \text{NBN }50\text{ Mbps}& :8000\text{ s}\approx 2\text{ h }13\text{ m}\text{LAN }1\text{ Gbps}:400\text{ s}=6\text{ m }40\text{ s}\end{array}$$

⚠️ Common Mistakes

• 💡 Bytes ≠ bits ➔ rates are in bits/s, file sizes in bytes — forgetting ×8 is the classic mark-loss.
• 💡 Switch vs router ➔ switch joins computers inside one LAN; router joins networks — the boundary word decides.

🧠 Active Recall

Define the four network components and place them in the LAN/BN/MAN/WAN ladder.

Answer

• Short answer: Client = user access; server = shared data/software; switch = intra-LAN connector; router = inter-network connector; reach ladder LAN → BN → MAN → WAN by distance.
• Why: Internet = network of networks ➔ routers are precisely the glue points between the ladder’s rungs.

How long does a 10 GB file take at 100 Mbps? Show the unit chain.

Answer

• Short answer: $10$ GB $=80$ Gbit $=80000$ Mbit ÷ $100$ Mbps $=800$ s ≈ $13$ min $20$ s.
• Why: bits ÷ bits/s ➔ convert bytes→bits first, then divide by the rate; keep units visible at every step.