CCNA ITN: Module 4

physical connection

required before any network communication, can be wired or wireless

Ethernet NIC

network interface card for wired connections

WLAN NIC

network interface card for wireless connections

physical layer (OSI)

transports bits across the medium by encoding frames as signals

signals

represent bits as electrical, optical, or radio wave forms

physical layer components

electronic circuits, connectors, media, NICs, interfaces

standards organizations

ISO, TIA/EIA, ITU, ANSI, IEEE, FCC, ETSI govern physical layer

encoding

converts data into recognizable patterns or codes for transmission

bit representation

signals like electrical pulses, light, or radio waves

bandwidth

capacity of a medium to carry data (kbps, Mbps, Gbps)

latency

time delay for data to travel from source to destination

throughput

rate of successful data transfer over time

goodput

throughput minus protocol overhead (usable data rate)

copper cabling

common, low-cost, low-resistance media, subject to EMI and attenuation

EMI

electromagnetic interference, disrupts signals

RFI

radio frequency interference

crosstalk

interference from adjacent wires

attenuation

signal degradation over distance

shielding

reduces interference using metallic materials

UTP

unshielded twisted pair cable, most common

STP

shielded twisted pair, better protection but harder to install

coaxial cable

older copper medium, still used for antennas and cable internet

RJ-45

connector used with UTP and STP cables

UTP structure

4 twisted pairs, plastic sheath, outer jacket

STP structure

outer jacket, shield, foil, twisted pairs

coaxial structure

copper core, insulation, shield, jacket

UTP cable design

pairs wires to cancel EMI/RFI

cabling standards

TIA/EIA for UTP, IEEE for electrical categories

Category 3

voice communications

Category 5/5e

supports 100/1000 Mbps data

Category 6/7

supports 10 Gbps

Category 8

supports 40 Gbps

straight-through cable

used to connect host to switch or switch to router

crossover cable

used to connect similar devices

incorrect cable

no damage, but prevents communication

T568A color order

green stripe, green, orange stripe, blue, blue stripe, orange, brown stripe, brown

T568B color order

orange stripe, orange, green stripe, blue, blue stripe, green, brown stripe, brown

Ethernet straight-through

both ends are T568A or both T568B

Ethernet crossover

one end T568A, one T568B

rollover cable

Cisco proprietary cable for console access

fiber optic cabling

transmits data using light, high speed and distance, immune to EMI/RFI

optical fiber

thin glass strand encoding bits as light pulses

single-mode fiber

small core, long distance, uses lasers

multimode fiber

larger core, uses LEDs, shorter distances (up to 550m)

fiber use cases

enterprise, FTTH, long-haul, submarine networks

optical fiber connectors

terminate fiber cables, vary by size and coupling

ST connector

twist-lock, round

SC connector

square, push-pull

LC connector

small SC type

LC duplex

connector using two fibers

fiber patch cords

examples: orange SC-SC (multimode), yellow LC-LC (single-mode)

fiber vs copper

fiber: high speed/distance, immune to EMI

copper: cheaper, easier to install

wireless media

radio or microwave signals carrying data bits

wireless benefits

mobility, no wiring needed

wireless limits

interference, shared bandwidth, weaker security

Wi-Fi

standard IEEE 802.11, uses CSMA/CA

Bluetooth

standard IEEE 802.15, WPAN over 1-100 meters

WiMAX

standard IEEE 802.16, wireless broadband

Zigbee

standard IEEE 802.15.4, for IoT devices

WLAN

includes wireless access points and wireless NICs

wireless NIC

provides wireless connectivity to hosts

WLAN infrastructure

wireless AP connects users to the wired network

wireless security

requires strict admin policies to avoid unauthorized access