Network Media
Communication transmits across a network on media. The media provides the channel over which the message travels from source to destination.
Types of Media
Modern networks primarily use three types of media to interconnect devices, as shown in the figure:
- Metal wires within cables - Data is encoded into electrical impulses.
- Glass or plastic fibers within cables (fiber-optic cable) - Data is encoded into pulses of light.
- Wireless transmission - Data is encoded via modulation of specific frequencies of electromagnetic waves.
Choosing Network Media
The four main criteria for choosing network media are these:
- What is the maximum distance that the media can successfully carry a signal?
- What is the environment in which the media will be installed?
- What is the amount of data and at what speed must it be transmitted?
- What is the cost of the media and installation?
Fiber Optic
Fiber-optic cable can be either glass or plastic with a diameter about the same as a human hair and it can carry digital information at very high speeds over long distances. Because light is used instead of electricity, electrical interference does not affect the signal.
They have a very high bandwidth, which enables them to carry very large amounts of data. Fiber is used in backbone networks, large enterprise environments, and large data centers. It is also used extensively by telephone companies.
Twisted-Pair
Ethernet technology generally uses twisted-pair cables to interconnect devices. Because Ethernet is the foundation for most local networks, twisted-pair is the most commonly encountered type of network cabling.
Ethernet cables are used for wired networking, providing a physical medium for data transmission. The most common type used today is Category 5e (Cat5e), Category 6 (Cat6), and Category 6a (Cat6a) cables. These cables consist of four twisted pairs of copper wires, enclosed in an outer sheath.
Why Twisted Pairs?
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Reduces Electromagnetic Interference (EMI): Twisting the wires minimizes crosstalk and external interference.
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Improves Signal Integrity: Ensures data transmission is stable over longer distances.
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Prevents Signal Degradation: Helps maintain consistent speeds in network communications.
Why Different Colors?
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Standardization: Ensures consistency across installations.
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Easy Troubleshooting: Allows network technicians to quickly identify wires.
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Functionality: Different pairs are used for transmitting and receiving data, with some reserved for Power over Ethernet (PoE).
Ethernet Wiring Standards
When terminating an Ethernet cable into an RJ45 connector, we must follow a specific wiring order. The most common standard in modern installations is T568B:
| Pin | Color | Function |
|---|---|---|
| 1 | White/Orange | Transmit Data + |
| 2 | Orange | Transmit Data - |
| 3 | White/Green | Receive Data + |
| 4 | Blue | Unused (or Power in PoE) |
| 5 | White/Blue | Unused (or Power in PoE) |
| 6 | Green | Receive Data - |
| 7 | White/Brown | Unused (or Power in PoE) |
| 8 | Brown | Unused (or Power in PoE) |
To go further
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T568B became more widely used because AT&T and other telecom companies adopted it for their installations.
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Ethernet cables use differential signaling, where each data signal has a + (positive) wire and a - (negative) wire.
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Transmit Data (+/-): These pairs are used for sending data from the device. The Transmit + (Tx+) and Transmit - (Tx-) wires carry the same data but in opposite phases (one is the inverse of the other). The receiving device subtracts the two signals, which cancels out noise picked up along the cable. This method improves data integrity and reduces electromagnetic interference (EMI).
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Receive Data (+/-): These pairs receive incoming data.
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Unused (or Power in PoE): Some pairs are not used in standard Ethernet transmission but can carry electrical power when using Power over Ethernet (PoE) technology. PoE allows network devices like IP cameras, access points, and VoIP phones to be powered directly through the Ethernet cable, eliminating the need for separate power cables.
Keystone Wall Plates
A keystone wall plate is a structured cabling solution that allows for easy installation of Ethernet jacks in walls.
It consists of:
- Keystone Jack: A female connector for Ethernet cables.
- Wall Plate: A panel where the jack is mounted.
- Punch-down Block: Used to terminate the Ethernet cable securely. (see wiring picture below)
Benefits of Using Keystone Jacks
- Provides a cleaner and more organized networking setup.
- Reduces wear and tear on cables by securing them inside the wall.
- Allows modular expansion (e.g., adding more ports easily).