Networking Explained, Second Edition
An in-depth explanation of all things networking.
TABLE OF CONTENTS Networking Explained, Second Edition
Chapter 4: Physical Layer Concepts
Overview
In this chapter we present an overview of the first layer of the OSI model, namely, the physical layer. This is the "touch-and-feel" layer. It provides for the physical transmission of data. As part of our presentation we discuss various transmission media, including twisted pair, coaxial, and fiber-optic cables. We also examine various forms of wireless and satellite communications. An outline of the major topics we discuss follows:
-
Physical Layer Issues (Questions 1 8)
-
Analog vs. Digital Communications (Questions 9 22)
-
Bandwidth vs. Throughput and Data Rate vs. Baud Rate (Questions 23 27)
-
Noise (Questions 28 30)
-
Shannon's Limit (Questions 31 38)
-
Multiplexers and Multiplexing Strategies (Questions 39 43)
-
Switching Strategies (Questions 44 45)
-
Physical and Electrical Characteristics of Wire (Questions 46 54)
-
UTP, STP, and IBM Cable (Questions 55 65)
-
Coaxial Cable (Questions 66 69)
-
Fiber-Optic Cable (Questions 70 81)
-
Wireless Media (Questions 82 96)
-
Satellite Communications (Questions 97 104)
Physical Layer Issues
-
What is the physical layer?
The physical layer is the lowest layer (layer 1) of the OSI Reference Model. The OSI model was discussed in Chapter 2.
-
What does the physical layer do?
Before sending data on the network, the physical layer on the local node must process the data stream, translating frames received from the data link layer (layer 2) into electrical, optical, or electromagnetic signals representing 0 and 1 values, or bits. Frames, which are discussed in more detail in Chapter 5, are specially formatted bit sequences that incorporate both data and control information. The local physical layer is responsible for transmitting these bit sequences...
Copyright Butterworth-Heinemann 2002 under license agreement with Books24x7
