Overview
This lecture covers the types, structures, and standards of network cabling, including twisted pair, coaxial, shielding methods, and special installation environments like plenum spaces.
Foundations of Network Cabling
- Reliable network performance depends on proper cabling installation and quality.
- Wireless networks still rely on cables to connect access points to the network.
Twisted Pair Cables
- Twisted pair cables contain pairs of wires twisted together to reduce interference.
- Each wire pair carries equal and opposite signals (transmit plus and minus).
- Different twist rates help receivers identify and filter out interference.
- Twisted pair cables follow standards that define minimum capabilities.
- Minimum cable category must match the Ethernet standard (e.g., Category 5 for 1000Base-T).
- Category 5e (enhanced) replaces deprecated Category 5; supports gigabit Ethernet up to 100 meters.
- 10Gbps Ethernet requires at least Category 6 cable (unshielded: 55m; shielded: 100m); Category 6A supports 100m.
Cable Standards and Categories
- Ethernet standards (e.g., IEEE 802.3) specify required cable categories.
- Cable categories are marked on the cable sheath.
Coaxial Cables
- Coaxial cables consist of a central conductor and outer shielding; used for cable modems and digital cable.
- "Coaxial" means conductors share a common axis.
Shielding Types
- Unshielded Twisted Pair (UTP): no shielding.
- Shielded Twisted Pair (STP): shielding around pairs and/or the entire cable to protect against interference.
- Cable markings: U = unshielded, S = braided shield, F = foil shield.
- Markings such as S/FTP indicate braided shielding overall with foil shielding on pairs.
Specialized Cable Types & Installation Environments
- Direct burial Ethernet cables are waterproofed for underground use, often gel-filled and shielded.
- Drain wires are used for electrical grounding in outdoor or underground cables.
- Plenum spaces exist above drop ceilings and can carry air, smoke, and fire in a building.
- Cables in plenum spaces require fire-rated jackets made from FEP or low-smoke PVC, as opposed to regular PVC.
Key Terms & Definitions
- Twisted Pair Cable — Cable with pairs of wires twisted to reduce electromagnetic interference.
- Category 5/5e/6/6A Cable — Standards for twisted pair cables defining supported speeds and shielding features.
- Unshielded Twisted Pair (UTP) — Twisted pair cable without additional shielding.
- Shielded Twisted Pair (STP) — Twisted pair cable with shielding to block interference.
- Coaxial Cable — Copper cable with an inner conductor and external shield, used for high-speed transmissions.
- Plenum — Air circulation space in buildings, requiring special fire-resistant cabling.
- Direct Burial Cable — Cable designed to be safely installed underground.
- Drain Wire — Wire used to ground a cable for electrical safety.
Action Items / Next Steps
- Check the printed markings on existing cables to confirm category and shielding.
- Consult IEEE 802.3 standards for appropriate cabling for network upgrades.
- Use plenum-rated cables in all ceiling or air-handling spaces as required by building codes.