Overview
This lecture covers the importance of network cabling, focusing on twisted pair and coaxial cables, cable categories and standards, shielding types, special cable uses, and fire safety considerations in cabling installations.
Network Cabling Basics
- Network cables (copper, fiber) are critical for connecting computers and ensuring application functionality.
- Wireless networks also rely on cables at access points to connect to the wired infrastructure.
- Poor cabling can cause network failures and unreliable applications.
Twisted Pair Cables
- Twisted pair cables are widely used in Ethernet networks and consist of pairs of wires twisted together.
- Each pair carries equal and opposite signals (transmit plus and minus) to reduce interference.
- Different twist rates in each pair help the receiver identify and correct interference.
- Cable construction and performance are defined by industry standards specifying minimum capabilities.
Cable Categories & Standards
- Ethernet standards (IEEE 802.3) specify the minimum cable category required for each network type.
- Category 5 supports 1,000BASE-T (Gigabit Ethernet) up to 100 meters, but is deprecated in favor of Category 5e (enhanced).
- Category 5e and Category 6 can support higher speeds, with Category 6 required for 10GBASE-T (10 Gb Ethernet).
- Unshielded Category 6 runs up to 55 meters; shielded Category 6 and Category 6A (augmented) support 100 meters at 10 Gb speeds.
Copper Cable Types & Shielding
- Coaxial cables (coax) have an inner conductor and outer shield, used for cable modems and digital cable.
- Unshielded twisted pair (UTP) has no shielding; shielded twisted pair (STP) has shielding to protect from interference.
- Cable shielding abbreviations: U = Unshielded, S = Braided Shielding, F = Foil Shielding; “TP” = Twisted Pair.
- Abbreviations indicate shielding for the cable and for individual pairs, e.g., S/FTP is shielded outer, foil per pair.
Special Purpose Ethernet Cables
- Direct burial STP cables are waterproof and gel-filled for underground installation; they include shielding and a drain wire for grounding.
- These cables are structurally like indoor shielded cables but built to withstand outdoor conditions.
Plenum and Fire-Safe Cabling
- Plenum space is the open area above drop ceilings where air circulates and smoke can travel in a fire.
- Network cables in plenum must have fire-rated jackets (FEP or low-smoke PVC) to reduce toxic fumes and fire spread.
- Plenum-rated cables are less flexible but necessary for installations above drop ceilings.
Key Terms & Definitions
- Twisted Pair Cable — Wires twisted together to reduce interference.
- Coaxial Cable — Cable with an inner conductor and outer shield, used for high-speed data and TV.
- UTP (Unshielded Twisted Pair) — No shielding around wire pairs.
- STP (Shielded Twisted Pair) — Shielding protects against interference.
- Plenum — Building air space above ceilings used for air return.
- Plenum-Rated Cable — Fire-safe cable designed for installation in plenum spaces.
Action Items / Next Steps
- Check cable categories and shielding types in your network.
- Ensure plenum-rated cables are used above drop ceilings in building installations.