Chapter 2: Cabling and Technology

Physical Topology – The actual layout of devices and connections (cables, wireless, etc.).

Logical Topology – How data flows between nodes, regardless of physical connections.

A direct connection between two nodes using a single link (e.g., copper, fiber, wireless).

Nodes connect to a central device (switch, router, or server).

Evolved from mainframe-terminal setups.

Every device connects to every other, providing redundancy.

Can be wired or wireless.

If one link fails, traffic reroutes through another path.

Combines two or more physical topologies (e.g., star + ring + mesh).

Used to meet specific organizational needs.

A logical topology with three layers:

Core Layer – High-speed backbone (connects to WAN/Internet).

Distribution Layer – Routes/filters traffic, provides security (ACLs, load balancing).

Access Layer – Where end-user devices connect (switching, QoS, security).

Combines distribution and core layers into a single device (e.g., a Layer 3 switch).

A two-layer data center design:

Spine Switches (Layer 3) – Connect in a mesh.

Leaf Switches (Layer 2) – Connect end devices.

Reduces latency for east-west traffic (within the data center).

Physical = Actual hardware connections.

Logical = How data travels (e.g., three-tier hierarchy).

A two-layer version of the three-tier model that merges core and distribution layers.

A type of cable dating back to World War II, commonly used for TV and networking.

Has four main parts:

Inner conductor (core) – Carries the signal.

Insulator – Separates inner and outer conductors.

Outer conductor (mesh shield) – Protects against interference.

PVC sheath – Provides durability.

Determines the type, thickness, and conductor properties of the cable.

RG-6 is the modern standard (replaced RG-59).

75 ohms (Ω).

F-type (most common today) – Twist-on connector used for cable modems/TV.

BNC (older) – Twist-and-lock connector, used in legacy networks.

A twinaxial cable with two inner conductors sharing one outer conductor.

Used in SFP cables and some SATA cables.

Highly resistant to EMI (electromagnetic interference).

Durable (strong physical protection).

Inflexible (hard to install).

Expensive compared to some alternatives.

Cable modems, cable boxes, and other home devices.

An older twist-lock connector used in legacy systems.

A commonly used networking cable with pairs of twisted wires to reduce EMI (electromagnetic interference) and crosstalk.

Two main types:

UTP (Unshielded Twisted Pair) – No extra shielding (most common).

STP (Shielded Twisted Pair) – Has a grounded copper/foil shield for extra protection (used in industrial areas).

100 meters (~325 feet) before signal degrades.

RJ-45 (for Ethernet)

TIA-568A and TIA-568B (dictate wire pinouts).

Solid Core – Single copper wire (better for permanent installations, like in walls).

Stranded Core – Multiple thin wires (more flexible, used in patch cables).

Category Max Speed Max Distance Notes
Cat 5 100 Mbps – 1 Gbps 100m Mostly outdated.
Cat 5e 1 Gbps 100m Improved EMI protection.
Cat 6 10 Gbps 55m (100m for 1 Gbps) Better EMI/crosstalk resistance.
Cat 6a 10 Gbps 100m Full 10G support at full distance.
Cat 7 10 Gbps+ 100m Shielded, higher performance.
Cat 8 25-40 Gbps 30m Used for 40GBASE-T, data centers.

Transmits data as light pulses through a glass/plastic core.

Structure:

Core – Carries light signals.

Cladding – Reflects light back into the core.

Jacket – Outer protective layer.

Feature Single Mode Multimode
Light Source Laser (narrow, focused) LED (broader light)
Core Size Thinner (~9µm) Thicker (~50-62.5µm)
Distance Long (up to 100km+) Short (~2km max)
Color Code Yellow Orange (Aqua for OM3/4)

ST (Straight Tip) – Round, twist-lock (old, resembles BNC).

SC (Subscriber Connector) – Square, push-pull (common in older networks).

FC (Ferrule Connector) – Round, screws in (used in high-vibration environments).

LC (Lucent Connector) – Small, duplex (modern, high-density setups).

MTP/MPO – Multi-fiber (used in data centers for high-speed links).

PC (Physical Contact) – Slightly rounded (older, more signal loss).

UPC (Ultra Physical Contact) – More rounded, less loss (common today).

APC (Angled Physical Contact) – 8° angle, best for low reflection (used in high-precision apps).

Prevent fire spread & toxic smoke in buildings (like in The Towering Inferno).

Required by building/fire codes for safety.

Plenum spaces = Areas for HVAC airflow (e.g., above drop ceilings).

Riser cables rely on firestops to block fire between floors.

PVC cables are cheap but unsafe for enclosed spaces (toxic smoke).

The area between a drop ceiling and the actual ceiling, or between a raised floor and the true floor—used for HVAC air return.

Cabling with the highest fire resistance, designed for use in plenum spaces. Emits minimal smoke/toxins when burned.

Because it’s used in spaces with air circulation (HVAC), and safety/fire codes require low-smoke, fire-resistant materials.

Cabling meant to run vertically between floors. It has moderate fire resistance but is less resistant than plenum-rated.

Because proper installations include firestops to prevent fire spread.

The least fire-resistant cable type. It's cheaper but emits smoke and fumes when burned. Not allowed in walls or ceilings by most codes.

Catches fire quickly, produces noxious smoke and heavy charring.

Produces minimal smoke, resists burning better than PVC.

It’s inexpensive and useful for training or non-critical setups where fire risk is low.