CertiGuide to A+ (A+ 4 Real)  9  Chapter 13: Basic Networking Terminology       9  OSI Reference Model and Networking Protocols and Technologies

OSI Reference Model and Networking Protocols and Technologies 1 Layer 2 - Data Link Layer

The physical layer deals with the transfer of bits on physical components, such, as a coaxial cable, a twisted pair cable, or an optical fiber cable. The characteristics of the physical medium, such as attenuation¹⁷⁴ crosstalk, impedance ¹⁷⁵, etc., relate to this layer. To remember Layer 1 in as few words as possible, think of information transmission speeds and media types. One of the major characteristics of the communication channel is bandwidth¹⁷⁶.

Bandwidth is the measure of how much data can flow from one computer to another in a given amount of time. The unit of measurement is bits per second (bps) and is equal to 1 bit per one second.

Throughput is the actual measured bandwidth at a specific period. The throughput is often less then the maximum possible bandwidth of the medium that is being used.

OSI Reference Model and Networking Protocols and Technologies 1 Layer 2 - Data Link Layer