Chapter 3: Transmission Media & Hardware
Understanding the physical components that form the backbone of network communication
Introduction
Building on our understanding of network models, we now examine the physical components that enable communication. This chapter explores the transmission media that carry our data and the hardware devices that manage network traffic.
By the end of this chapter, you will be able to:
- Differentiate between guided and unguided transmission media
- Compare various cable types and their applications
- Explain the functions of hubs, switches, and routers
- Describe wireless technologies including Wi-Fi and 5G
- Understand key performance metrics like bandwidth and latency
Guided vs. Unguided Media
Guided (Wired) Media
Signals travel through a physical path:
- Examples: Fiber optic, coaxial, twisted pair cables
- Advantages: More secure, higher bandwidth, less interference
- Disadvantages: Installation cost, physical constraints
- Use Cases: Data centers, office networks, backbone infrastructure
Unguided (Wireless) Media
Signals propagate through the air:
- Examples: Wi-Fi, Bluetooth, cellular (5G)
- Advantages: Mobility, easy installation, scalability
- Disadvantages: Security concerns, interference, limited bandwidth
- Use Cases: Mobile devices, IoT, remote locations
Figure 1: Comparison of guided and unguided transmission media
Cables: Fiber, Coaxial, and UTP
Fiber Optic
- Structure: Glass core (50-62.5µm) with cladding (125µm)
- Types: Single-mode (long distance) vs multi-mode (short distance)
- Speed: 10Mbps to 100Gbps+
- Use Cases: Backbone networks, telecom, data centers
- Advantage: Immune to EMI, high bandwidth, low attenuation
Coaxial
- Structure: Central conductor with braided shield
- Types: RG-6 (video), RG-8 (thick Ethernet)
- Speed: 10Mbps to 1Gbps
- Use Cases: Cable TV, broadband Internet
- Advantage: Good noise immunity, moderate cost
UTP (Unshielded Twisted Pair)
- Structure: 4 twisted pairs (8 wires total)
- Categories: Cat5e (1Gbps), Cat6 (10Gbps), Cat6a (10Gbps/100m)
- Speed: 100Mbps to 10Gbps
- Use Cases: Ethernet LANs, telephone lines
- Advantage: Low cost, flexible, easy installation
| Cable Type | Max Distance | Bandwidth | Cost | Best For |
|---|---|---|---|---|
| Fiber Optic (SM) | 40+ km | 100Gbps+ | High | Backbone, long-distance |
| Fiber Optic (MM) | 550m | 10Gbps | Medium-High | Data centers, campus |
| Coaxial (RG-6) | 500m | 1Gbps | Medium | Cable TV, broadband |
| UTP (Cat6) | 100m | 10Gbps | Low | Office networks |
Common Pitfall
Using incorrect cable categories can limit network performance. For example, using Cat5 cable for a 10Gbps connection will fail - always verify cable specifications match your speed requirements.
Network Devices: Hubs, Switches, and Routers
Hubs
- Layer: Physical (Layer 1)
- Function: Basic signal repeating
- Operation: Broadcasts to all ports
- Speed: Typically 10/100Mbps
- Status: Largely obsolete
Switches
- Layer: Data Link (Layer 2)
- Function: Intelligent forwarding
- Operation: Learns MAC addresses
- Speed: 1Gbps to 100Gbps
- Features: VLANs, port security
Routers
- Layer: Network (Layer 3)
- Function: Inter-network routing
- Operation: Uses IP addresses
- Features: NAT, firewall, DHCP
- Use Case: Connecting networks
Figure 2: Network device hierarchy showing how traffic flows through different devices
Device Comparison
| Feature | Hub | Switch | Router |
|---|---|---|---|
| OSI Layer | 1 | 2 (or 3 for multilayer) | 3 |
| Address Used | None | MAC | IP |
| Traffic Handling | Broadcasts | Selective forwarding | Routing between networks |
| Collision Domain | Single | Per port | Per interface |
| Modern Usage | Rare | Ubiquitous | Essential |
Network Interface Cards (NICs)
What is a NIC?
A Network Interface Card (NIC) is the hardware component that connects a device to a network. Modern computers often have NICs built into the motherboard.
Types of NICs
- Wired NICs: Ethernet ports (RJ-45) supporting various speeds (1Gbps common)
- Wireless NICs: Wi-Fi adapters supporting 802.11 standards
- Specialized NICs: Fiber optic, high-speed (10Gbps+), or low-latency variants
NIC Configuration
Key settings to check:
- MAC Address: Unique hardware identifier
- Speed/Duplex: Auto-negotiation or manual (100Mbps/1Gbps, full/half duplex)
- IP Configuration: DHCP or static IP assignment
- Advanced Features: Wake-on-LAN, offloading
Windows: View NIC Details
ipconfig /all
Troubleshooting Tip
If experiencing network issues, first verify the NIC's link light (physical connection), then check for driver updates. Mismatched duplex settings are a common cause of performance problems.
Wireless Technologies
Wi-Fi (IEEE 802.11)
- Standards: 802.11ac (Wi-Fi 5), 802.11ax (Wi-Fi 6)
- Bands: 2.4GHz (range), 5GHz (speed), 6GHz (Wi-Fi 6E)
- Speed: 150Mbps to 9.6Gbps (Wi-Fi 6)
- Range: ~50m indoors, affected by obstacles
- Use Cases: Home/office networks, public hotspots
Bluetooth
- Versions: 5.0, 5.1, 5.2 (current as of 2025)
- Range: ~10m (Class 2 devices)
- Speed: 1-3Mbps (BLE), up to 50Mbps (5.2)
- Features: Low energy (BLE), mesh networking
- Use Cases: Peripherals, audio, IoT devices
5G Cellular
- Speeds: 100Mbps to 10Gbps (theoretical)
- Latency: 1-10ms (ultra-low latency)
- Bands: Sub-6GHz, mmWave (24-100GHz)
- Features: Network slicing, massive MIMO
- Use Cases: Mobile broadband, IoT, autonomous vehicles
Figure 3: Wireless technology comparison showing coverage areas and typical applications
Wi-Fi Standards Evolution
| Standard | Year | Max Speed | Frequency | Features |
|---|---|---|---|---|
| 802.11b | 1999 | 11Mbps | 2.4GHz | First widely adopted |
| 802.11g | 2003 | 54Mbps | 2.4GHz | OFDM modulation |
| 802.11n | 2009 | 600Mbps | 2.4/5GHz | MIMO, 40MHz channels |
| 802.11ac | 2013 | 3.5Gbps | 5GHz | MU-MIMO, 160MHz |
| 802.11ax (Wi-Fi 6) | 2019 | 9.6Gbps | 2.4/5/6GHz | OFDMA, TWT |
Performance Metrics
Bandwidth
- Maximum data transfer rate
- Measured in bits per second (bps)
- Common units: Mbps, Gbps
- Example: Cat6 cable = 10Gbps
Latency
- Time for data to travel
- Measured in milliseconds (ms)
- Factors: distance, medium, processing
- Example: Fiber ≈ 5ms/1000km
Attenuation
- Signal loss over distance
- Measured in decibels (dB)
- Mitigation: repeaters, amplifiers
- Example: UTP ≈ 20dB/100m
Comparing Media Performance
| Media Type | Typical Bandwidth | Latency | Attenuation |
|---|---|---|---|
| Fiber Optic | 10Gbps-100Gbps | Very Low | 0.2dB/km |
| UTP Cat6 | 10Gbps | Low | 20dB/100m |
| Coaxial | 1Gbps | Medium | 10dB/100m |
| Wi-Fi 6 | 9.6Gbps | Medium | High (varies) |
| 5G mmWave | 10Gbps | Very Low | Very High |
Practical Example: Configuring a Switch in Packet Tracer
Let's configure a basic Cisco switch with VLANs and port security:
Step 1: Access CLI
- Drag a 2960 switch to the workspace
- Connect to console port or double-click the device
-
Enter privileged EXEC mode:
enable
Step 2: Basic Configuration
configure terminal
hostname Office-Switch
enable secret MySecurePassword
service password-encryption
Step 3: Configure VLANs
vlan 10
name Sales
vlan 20
name Engineering
exit
Step 4: Assign Ports
interface range fastEthernet 0/1-12
switchport mode access
switchport access vlan 10
exit
interface range fastEthernet 0/13-24
switchport mode access
switchport access vlan 20
exit
Best Practice
Always add port security to prevent unauthorized devices from connecting:
interface range fastEthernet 0/1-24
switchport port-security
switchport port-security maximum 1
switchport port-security violation restrict
end
Visualizing Transmission Media
Figure 4: Interactive comparison of fiber optic, coaxial, and UTP cable structures
How to Read This Visualization
The interactive diagram shows:
- Fiber Optic: Core/cladding structure with light propagation
- Coaxial: Central conductor with dielectric and shielding
- UTP: Twisted pairs with color-coded insulation
Chapter Summary
Key Concepts
- Guided media (wired) offers reliability while unguided (wireless) provides mobility
- Fiber optic provides the highest bandwidth and lowest attenuation
- Switches operate at Layer 2 (MAC) while routers work at Layer 3 (IP)
- Modern wireless technologies like Wi-Fi 6 and 5G deliver multi-gigabit speeds
Best Practices
- Use fiber for backbone connections requiring high bandwidth
- Implement VLANs on switches for network segmentation
- Choose Cat6 or higher UTP for new Ethernet installations
- For wireless, prefer 5GHz band when possible for less interference
- Regularly update NIC drivers for optimal performance
Further Reading
- Books: "Computer Networks" by Andrew Tanenbaum (Chapter 4 - The Medium Access Control Sublayer)
- Standards: IEEE 802.3 (Ethernet), IEEE 802.11 (Wi-Fi)
- Vendor Documentation: Cisco Catalyst 2960 Configuration Guides
- Tools: Wireshark for protocol analysis, Cisco Packet Tracer for network simulation