The Physical Layer

What are the three main types of physical network media?

1. Copper wire (twisted pair/coaxial)

2. Fiber optic cable

3. Wireless transmission

What are the differences between UTP, STP, and coaxial cable?

• UTP: Unshielded twisted pair (basic, susceptible to interference)

• STP: Shielded twisted pair (foil wrapped, less interference)

• Coaxial: Center conductor with braided outer layer (best shielding but more expensive)

What are the current categories of UTP cabling and their speeds?

• Cat 5: 100 Mbps

• Cat 6: 250 Mbps

• Cat 7: 10 Gbps (emerging standard)

What are the advantages of fiber optic cable?

• Virtually error-free

• Long distance transmission

• High bandwidth capacity

• Immune to electromagnetic interference

What is WDM/DWDM and why is it important?

Wavelength Division Multiplexing allows multiple signals over one fiber using different light wavelengths, dramatically increasing capacity without new cables.

What are the main wireless networking standards?

• Wi-Fi (IEEE 802.11) for LANs

• Bluetooth (IEEE 802.15) for PANs/BANs

What are the key challenges of wireless networking?

• Susceptibility to interference

• Security vulnerabilities

• Range limitations

Why should network troubleshooting start at the Physical layer?

Because physical connection problems can cause symptoms that appear to be higher-layer issues, making them the most likely root cause.

What makes coaxial cable different from twisted pair?

Coax has a central conductor surrounded by insulating layer and braided outer conductor, providing better shielding in a single cable.

How has fiber optic technology impacted long-distance communication costs?

WDM allows existing fibers to carry 64-128x more data, reducing per-bit transmission costs and enabling lower service prices.

What are typical applications for Bluetooth technology?

Short-range connections between devices like phones, PDAs, laptops, and peripherals (PANs/BANs).

What factors contribute to fiber optic's high bandwidth capacity?

• Light-based transmission (higher frequency than electrical signals)

• Low signal attenuation

• WDM multiplexing capability

Why is STP more expensive than UTP?

Due to additional shielding materials and more complex construction required to reduce electromagnetic interference.