思科网络技术学院理事会 . http://www.catc.edu.cn 1
OSI Physical Layer
Network Fundamentals – Chapter 8
2思科网络技术学院理事会 . http://www.catc.edu.cn
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
3思科网络技术学院理事会 . http://www.catc.edu.cn
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
思科网络技术学院理事会 . http://www.catc.edu.cn 4
8.1 The Physical Layer – Communication Signals
5思科网络技术学院理事会 . http://www.catc.edu.cn
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.
6思科网络技术学院理事会 . http://www.catc.edu.cn
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.
7思科网络技术学院理事会 . http://www.catc.edu.cn
8.1.2 Physical Layer - Operation There are three basic forms of network media on
which data is represented:
- Copper cable
- Fiber
- Wireless
8思科网络技术学院理事会 . http://www.catc.edu.cn
8.1.3 Physical Layer - Standards Comparison of Physical layer standards and upper
layer standards
9思科网络技术学院理事会 . http://www.catc.edu.cn
8.1.3 Physical Layer - Standards
Standards for the Physical layer specify signal, connector, and cabling requirements.
10思科网络技术学院理事会 . http://www.catc.edu.cn
8.1.3 Physical Layer - Standards
Standards for the Physical layer specify signal, connector, and cabling requirements.
11思科网络技术学院理事会 . http://www.catc.edu.cn
8.1.3 Physical Layer - Standards
Standards for the Physical layer specify signal, connector, and cabling requirements.
12思科网络技术学院理事会 . http://www.catc.edu.cn
8.1.3 Physical Layer - Standards
Standards for the Physical layer specify signal, connector, and cabling requirements.
13思科网络技术学院理事会 . http://www.catc.edu.cn
8.1.4 Physical Layer Fundamental Principles The three fundamental functions of the Physical layer
are:
- The physical components
- Data encoding
- Signaling
思科网络技术学院理事会 . http://www.catc.edu.cn 14
8.2 Physical Signaling and
Encoding:
Representing Bits
15思科网络技术学院理事会 . http://www.catc.edu.cn
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
16思科网络技术学院理事会 . http://www.catc.edu.cn
8.2.1 Signaling Bits for the Media
Method of signaling:
- Non Return to Zero (NRZ) Signaling
- Manchester Encoding
- 4B/5B
17思科网络技术学院理事会 . http://www.catc.edu.cn
8.2.2 Encoding – Grouping Bits
One way to provide frame detection is to begin each frame with a pattern of signals representing bits.
18思科网络技术学院理事会 . http://www.catc.edu.cn
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
19思科网络技术学院理事会 . http://www.catc.edu.cn
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.
20思科网络技术学院理事会 . http://www.catc.edu.cn
8.2.3 Data carrying Capacity
Data Throughput and Goodput
思科网络技术学院理事会 . http://www.catc.edu.cn 21
8.3 Physical Media –
Connecting Communication
22思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.1 Types of Physical Media Several media characteristics defined by Physical layer
standards.
23思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.1 Types of Physical Media Several media characteristics defined by Physical layer
standards.
24思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.2 Copper Media
The types of copper cabling include:
- Coaxial cable
- Twisted-pair cable
· Unshielded Twisted-pair
· Shielded Twisted-pair
25思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.2 Copper Media External Signal Interference
26思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.3 Unshielded Twisted Pair (UTP) Cable The basic characteristics of UTP cable
27思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.3 Unshielded Twisted Pair (UTP) Cable
UTP Cable Types
- Ethernet Straight-through
- Ethernet Crossover
- Rollover
28思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.4 Other Copper Cable Coaxial cable
29思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.4 Other Copper Cable Coaxial cable
30思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.4 Other Copper Cable
Shielded Twisted-Pair (STP) Cable
31思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.5 Copper Media Safety Types of safety issues when working with copper
cabling
32思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.6 Fiber Media
Fiber Media Cable Construction
33思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.6 Fiber Media
Fiber Media Cable Construction
34思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.6 Fiber Media
Fiber provides full duplex communications with a cable dedicated to each direction.
35思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.6 Fiber Media Fiber optic cables can be broadly classified into two
types: single-mode and multimode.
i
36思科网络技术学院理事会 . http://www.catc.edu.cn
8.2.7 Wireless Media Wireless media carry electromagnetic signals at radio
and microwave frequencies that represent the binary digits of data communications.
37思科网络技术学院理事会 . http://www.catc.edu.cn
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)
38思科网络技术学院理事会 . http://www.catc.edu.cn
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
39思科网络技术学院理事会 . http://www.catc.edu.cn
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.
40思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.8 Media Connectors Common Copper Media Connectors
41思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.8 Media Connectors
Correct Connector Termination
42思科网络技术学院理事会 . http://www.catc.edu.cn
8.3.8 Media Connectors
Common Optical Fiber Connectors
44思科网络技术学院理事会 . http://www.catc.edu.cn
Category 5 UTP Cable Tests
Lab 8.4.1: Media Connectors Lab Activity
46思科网络技术学院理事会 . http://www.catc.edu.cn