Topic 4 (Physical Layer_

encodes it as a series of signals

The physical layer accepts a complete frame from the Data Link Layer and _______________ that are transmitted to the local media

Physical Layer

Accepts a complete frame from the Data Link Layer and encodes it as a series of signals that are transmitted to the local media

Physical Layer

Transports bits across the network media

Physical Layer

The next device in the path to the destination receives the bits and re- encapsulates the frame, then decides what to do with it.

Physical Components, Encoding, Signaling

What are the three functional areas in the physical layer

Physical Components

hardware devices, media, and other connectors that transmit the signals.

Encoding

converts the stream of bits into a format recognizable by the next device in the network path.

The signaling method

is how the bit values, “1” and “0” are represented on the physical medium.

Bandwidth

the capacity at which a medium can carry data.

Latency

the amount of time, including delays, for data to travel from one given point
to another

Throughput

the measure of the transfer of bits across the media over a given
period of time

Overhead

the amount of data traffic required for establishing sessions,
acknowledgments, and encapsulation

Goodput

the measure of usable data transferred over a given period of time

Goodput = Throughput - Overhead

Goodput formula

Copper Cabling

is the most common type of cabling used in networks today. It is inexpensive, easy to install, and has low resistance to electrical current flow.

Attenuation, Electromagnetic interference and Radio Frequency Interference, Crosstalk

What are the limitations of copper cabling

Attenuation

the longer the electrical signals have to travel, the weaker they get.

Electromagnetic Interference and Radio Frequency Interference, Crosstalk

What are the two sources that is susceptible to interference:

Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI)

• ________ signals can distort and corrupt the data signals being carried by copper media.
• Sources of _______ include fluorescent lights or electric motors.

to reduce attenuation.

Strict adherence to cable length limits ___________.

to reduce EMI and RFI

Using metallic shielding and grounding ____________.

to reduce crosstalk

Twisting opposing circuit pair wires together __________.

Unshielded Twisted-Pair Cable

Electromagnetic Interference

What does EMI stand for

Radio Frequency Interference

What does RFI stand for

Shielded Twisted-Pair Cable

Coaxial Cable

Unshielded Twisted-Pair

What does UTP stand for

Shielded Twisted-Pair

What does STP stand for

UTP

is the most common networking media.

UTP and STP

Terminated with RJ-45 connectors

UTP and STP

Interconnects hosts with intermediary network devices

• The outer jacket serves as a protective layer that shields the internal copper wiring from physical wear and environmental damage.

• The twisting of the wire pairs is a design feature that cancels out electromagnetic interference to maintain signal integrity.

• Each wire is encased in color-coded plastic insulation to prevent electrical contact between conductors and simplify identification.

Key Characteristics of UTP

STP

Better noise protection than UTP

STP

More expensive than UTP

STP

Harder to install than UTP

1. The outer jacket acts as a durable shield that prevents physical impact or environmental hazards from damaging the internal copper wiring.

2. The braided or foil layer serves as a primary barrier against external electromagnetic and radio frequency interference (EMI/RFI).

3. Individual foil wraps around each wire pair provide a second layer of protection to eliminate internal cross-talk between the pairs.

4. Color-coded plastic insulation prevents electrical shorts by isolating individual wires while making them easy to identify for termination.

Key Characteristics of STP

1. Outer cable jacket to prevent minor physical
damage
2. A woven copper braid, or metallic foil, acts as
the second wire in the circuit and as a shield
for the inner conductor.
3. A layer of flexible plastic insulation
4. A copper conductor is used to transmit the
electronic signals.

Coaxial Cable consists of what

BNC, N, F.

There are different types of connectors used
with coax cable: _________

Wireless installations

attach antennas to wireless devices

Cable internet installations

customer premises wiring

Cancellation and Varying the number of twists per wire pair

Because the UTP cable does not use shielding to counter the effects of EMI and RFI, the negative effect of crosstalk is reduced by:

Cancellation

The wires in a circuit are paired, so that the magnetic fields in a pair are exactly opposite of each other, cancelling each other and any outside EMI and RFI signals.

Varying the number of twists per wire pair

Each colored pair is twisted a different number of times.

• Cable Types and Lengths
• Connectors
• Cable Termination
• Testing Methods

Standards for UTP are established by the TIA/EIA.
TIA/EIA-568 standardizes elements like:

• Category 3
• Category 5 and 5e
• Category 6

Electrical standards for copper cabling are established by the IEEE, which rates cable according to its performance. Examples include:

RJ-45 Connector

Poorly terminated UTP Cable

RJ-45 Socket

Properly Terminated UTP cable

Straight-through cable

between devices at different layers

Crossover cable

between devices at similar layers.

Rollover cable

for console connection to a router/switch port

Ethernet Straight-through

Host to Switch/Hub Switch to Router

Ethernet Crossover

Host to Host, Switch to Switch, Router to Router, Host to Router

Rollover

Host serial port to Router/Switch Console Port

Both ends T568A or T568B

What is the standard for the Ethernet Straight-through

One end T568A, other end T568B

What is the standard for the Ethernet Crossover

Cisco Proprietary

What is the standard for the rollover

• Very small core
• Uses expensive lasers
• Long-distance applications

Single-Mode Fiber

• Larger core
• Uses less expensive LEDs
• LEDs transmit at different angles
• Up to 10 Gbps over 550 meters

Multimode Fiber

greater

MMF has _____ dispersion than SMF

Enterprise Networks, Fiber-to-the-home (FTTH), Long-Haul Networks, Submarine Cable Networks

Fiber-optic cabling is now being used in four types of industry

Enterprise Networks

Used for backbone cabling applications and interconnecting infrastructure devices

Fiber-to-the-Home (FTTH)

Used to provide always-on broadband services to homes and small businesses

Long-Haul Networks

Used by service providers to connect countries and cities

Submarine Cable Networks

Used to provide reliable high-speed, high-capacity solutions capable of surviving in harsh undersea environments at up to transoceanic distances.

Straight-Tip(ST) Connectors

Lucent Connector(LC) Simplex Connectors

Subscriber Connector (SC)

Duplex Multimode LC Connectors

SC-SC MM Patch Cord

LC-LC SM Patch Cord

ST-LC MM Patch Cord

ST-SC SM Patch Cord

yellow jacket

A ___________ is for single-mode fiber cables and orange (or aqua) for multimode fiber cables

Wireless Media

It carries electromagnetic signals representing binary digits using radio or microwave frequencies. This provides the greatest mobility option.

Coverage area, Interference, Security, Shared medium

What are the limitations of wireless:

Coverage area

Effective coverage can be significantly impacted by the physical characteristics of the deployment location

Interference

Wireless is susceptible to interference and can be disrupted by many common devices

Security

Wireless communication coverage requires no access to a physical transmission media, so anyone can gain access to the transmission.

Shared medium

WLANs operate in half-duplex, which means only one device can send or receive at a time. Many users accessing the WLAN simultaneously results in reduced bandwidth for each user.

Wi-Fi

Wireless LAN (WLAN) technology

Bluetooth

Wireless Personal Area network (WPAN) standard

WiMAX

Uses a point-to-multipoint topology to provide broadband wireless access

Zigbee

Low data-rate, low power-consumption communications, primarily for Internet of Things (IoT) applications