Unit 2 Data Network Hardware

Layer 1: Physical Media & Infrastructure

Copper wire Ethernet cables operate at the Physical Layer by converting data bits into electrical pulses.  

Copper cables are susceptible to electromagnetic interference (EMI) and attenuation, limiting their maximum usable length to generally 100 meters.  

Unshielded twisted pair (UTP) is the most common copper cable, while shielded twisted pair (STP) includes protective foil or braiding to reduce EMI.  

RJ-45 connectors use T568A or T568B wiring schemes, with T568B being the standard for most network equipment manufacturers.  

Straight-through cables are used to connect different types of devices, whereas crossover cables are used to connect like devices.  

Fiber optic cables use light to encode bits and are completely immune to EMI.  

Single Mode Fiber (SMF) uses lasers and small cores for long distances of 10+ km, while Multi Mode Fiber (MMF) uses LEDs or VCSELs for shorter LAN distances.  

Common fiber optic connectors include the bayonet-style ST, the push/pull SC, the high-density LC, and the multi-fiber MPO.  

Network hubs operate strictly at Layer 1 by rebroadcasting received data out of every interface, placing all connected nodes within a single collision domain.  

Network cabling runs to an Intermediate Distribution Frame (IDF) using patch panels and a 110 punch-down block, which then patches into a Main Distribution Frame (MDF).  

Plenum-rated cable is self-extinguishing and must be used in horizontal air-handling spaces, while riser-rated cable is used vertically between floors and requires fire blocking.  

Troubleshooting tools include multimeters for electrical current, tone generators for tracing cables in walls, Time Domain Reflectometers (TDR) for detecting copper cable faults, and Optical Time Domain Reflectometers (OTDR) for fiber faults.  

Layer 2: Data Link & Switching

Switching operates at Layer 2 to forward data within a single logical LAN segment based on media access control (MAC) addresses.  

A MAC address is a unique 12-digit hexadecimal hardware address burned into a device's network interface card by the manufacturer.  

A collision domain is a network segment where data packets can collide on shared media.  

Each port on a network switch represents a separate collision domain, whereas all devices attached to a single hub share one collision domain.  

A broadcast domain is a logical subnet where a broadcast frame is forwarded to all connected devices.  

Network switches learn the MAC addresses of attached hosts and allow for full-duplex communication simultaneously.  

Unmanaged switches are simple plug-and-play devices, while managed switches allow for network configuration, monitoring, and security enhancements.  

Switch interfaces utilized to connect the switch to the larger network and consolidate traffic are known as trunk ports.  

Hierarchical LAN switched backbones utilize Core layer switches to manage traffic between segments, Distribution layer switches for intermediate handling, and Access layer switches to connect endpoint devices.  

Layer 3: Network & Routing

Routing operates at Layer 3 to forward data between different networks and broadcast domains based on Internet Protocol (IP) addresses.  

Layer 3 devices remove incoming frame headers, determine routes using packet headers, and add new frame headers before forwarding the data.  

Wi-Fi routers act as both a wireless access point and a wired switch, establishing peer-to-peer networks primarily for small offices and homes.  

Enterprise routers connect geographically distant LANs and external networks to support client-server architectures.  

Enterprise routers are modular, utilizing high-speed WAN interface cards (HWIC) and small form-factor pluggable (SFP) ports for physical connection customization.  

Layer 3 switches, or multi-layer switches, perform local MAC address switching for same-domain traffic and IP routing for external destinations.  

Wireless LAN Controllers (WLC) centralize the coordination of all wireless access points on an enterprise network to support seamless Layer 3 roaming without losing connectivity.  

Internet Access Technologies

Internet access is provided by an Internet Service Provider (ISP), with the Demarcation line separating the Provider Edge equipment from the Customer Edge equipment.  

Dedicated Internet Access (DIA) provides a private, uncontested connection with guaranteed bandwidth via leased lines.  

Integrated Services Digital Network (ISDN) is a legacy standard providing digital transmission over traditional analog telephone networks, currently being phased out for fiber.  

Broadband access is a shared connection with asymmetric, variable speeds that serves as an affordable option for homes and small networks.  

Cable modems convert digital signals for transmission over coaxial cables utilizing DOCSIS standards.  

Digital Subscriber Line (DSL) utilizes existing copper telephone lines to connect a subscriber to the ISP's fiber optic backbone.  

Fiber to the Home (FTTH) connects ISP infrastructure directly to the customer premises using an Optical Network Terminal (ONT) to convert light signals.  

Microwave internet provides wireless access through high-frequency radio signals, requiring direct line-of-sight between highly-directional antennas.  

Satellite internet uses geostationary or low-Earth orbit satellites to provide global access, though the signal distance introduces high latency.  

Cellular networks use base stations to distribute transmissions over geographic cells, coordinating handoffs for mobile users across network generations from 1G to 5G.