OSI Physical Layer
Network Fundamentals – Chapter 8
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Objectives

Explain the role of Physical layer protocols and
services in supporting communication across data
networks.
- Describe the role of signals used to represent bits as a frame
as the frame is transported across the local media

Describe the purpose of Physical layer signaling and
encoding as they are used in networks

Identify the basic characteristics of copper, fiber and
wireless network media

Describe common uses of copper, fiber and wireless
network media
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Context Index
 8.1 The Physical Layer – Communication Signals
 8.2 Physical Signaling and Encoding: Representing Bits
 8.3 Physical Media – Connecting Communication
 8.4 Labs – Media Connectors
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8.1 The Physical Layer
– Communication Signals
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8.1.1 Physical Layer - Purpose
 The OSI Physical layer provides the means to transport
across the network media the bits that make up a Data
Link layer frame.
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8.1.1 Physical Layer - Purpose
 The purpose of the Physical layer is to create the
electrical, optical, or microwave signal that represents
the bits in each frame.
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8.1.2 Physical Layer - Operation

There are three basic forms of network media on
which data is represented:
－Copper cable
－Fiber
－Wireless
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8.1.3 Physical Layer - Standards
 Comparison of Physical layer standards and upper
layer standards
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8.1.3 Physical Layer - Standards
 Standards for the Physical layer specify signal,
connector, and cabling requirements.
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8.1.3 Physical Layer - Standards
 Standards for the Physical layer specify signal,
connector, and cabling requirements.
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8.1.3 Physical Layer - Standards
 Standards for the Physical layer specify signal,
connector, and cabling requirements.
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8.1.3 Physical Layer - Standards
 Standards for the Physical layer specify signal,
connector, and cabling requirements.
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8.1.4 Physical Layer Fundamental Principles
 The three fundamental functions of the Physical layer
are:
－The physical components
－Data encoding
－Signaling
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8.2 Physical Signaling and Encoding:
Representing Bits
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8.2.1 Signaling Bits for the Media
 All communication from the human network becomes
binary digits, which are transported individually across
the physical media.
 Bits are represented on the medium by changing one or
more of the following characteristics of a signal:
－Amplitude
－Frequency
－Phase
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8.2.1 Signaling Bits for the Media
 Method of signaling:
－Non Return to Zero (NRZ) Signaling
－Manchester Encoding
－4B/5B
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8.2.2 Encoding – Grouping Bits
 One way to provide frame detection is to begin each
frame with a pattern of signals representing bits.
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8.2.2 Encoding – Grouping Bits
 A code group is a consecutive sequence of code bits
that are interpreted and mapped as data bit patterns.
 Advantages using code groups include:
－Reducing bit level error
－Limiting energy transmitted
－Distinguish data from control
－Better media error detection
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8.2.3 Data carrying Capacity
 Data transfer can be measured in three ways:
－Bandwidth
－Throughput
－Goodput
 Bandwidth
Digital bandwidth measures the amount of information that
can flow from one place to another in a given amount of time.
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8.2.3 Data carrying Capacity
 Data Throughput and Goodput
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8.3 Physical Media –
Connecting Communication
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8.3.1 Types of Physical Media
 Several media characteristics defined by Physical layer
standards.
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8.3.1 Types of Physical Media
 Several media characteristics defined by Physical layer
standards.
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8.3.2 Copper Media
 The types of copper cabling include:
－Coaxial cable
－Twisted-pair cable
· Unshielded Twisted-pair
· Shielded Twisted-pair
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8.3.2 Copper Media
 External Signal Interference
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8.3.3 Unshielded Twisted Pair (UTP) Cable
 The basic characteristics of UTP cable
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8.3.3 Unshielded Twisted Pair (UTP) Cable
 UTP Cable Types
－Ethernet Straight-through
－Ethernet Crossover
－Rollover
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8.3.4 Other Copper Cable
 Coaxial cable
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8.3.4 Other Copper Cable
 Coaxial cable
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8.3.4 Other Copper Cable
 Shielded Twisted-Pair (STP) Cable
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8.3.5 Copper Media Safety
 Types of safety issues when working with copper
cabling
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8.3.6 Fiber Media
 Fiber Media Cable Construction
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8.3.6 Fiber Media
 Fiber Media Cable Construction
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8.3.6 Fiber Media
 Fiber provides full duplex communications with a cable
dedicated to each direction.
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8.3.6 Fiber Media
 Fiber optic cables can be broadly classified into two
types: single-mode and multimode.
i
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8.2.7 Wireless Media
 Wireless media carry electromagnetic signals at radio
and microwave frequencies that represent the binary
digits of data communications.
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8.3.7 Wireless Media
 Types of Wireless Networks
－Standard IEEE 802.11
－Standard IEEE 802.15
－Standard IEEE 802.16
－Global System for Mobile Communications (GSM)
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8.3.7 Wireless Media
 The Wireless LAN
In general, a wireless LAN requires the following
network devices:
－Wireless Access Point (AP)
－Wireless NIC adapters
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8.3.7 Wireless Media
 WLAN Ethernet-based standards include:
 IEEE 802.11a - Operates in the 5 GHz frequency band and
offers speeds of up to 54 Mbps.
 IEEE 802.11b - Operates in the 2.4 GHz frequency band and
offers speeds of up to 11 Mbps.
 IEEE 802.11g - Operates in the 2.4 GHz frequency band and
offers speeds of up to 54 Mbps.
 IEEE 802.11n - The proposed standard defines frequency of
2.4 GHz or 5 GHz. The typical expected data rates are 100 Mbps
to 210 Mbps with a distance range of up to 70 meters.
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8.3.8 Media Connectors
 Common Copper Media Connectors
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8.3.8 Media Connectors
 Correct Connector Termination
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8.3.8 Media Connectors
 Common Optical Fiber Connectors
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8.4 Labs – Media Connectors
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Category 5 UTP Cable Tests
 Lab 8.4.1: Media Connectors Lab Activity
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Summary
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