July 2004
Beginner
408 pages
7h 31m
English
The upper layers of the Open System Interconnection (OSI) model, where user data is found, need the lower layers, like a train needs tracks to get from point A to B. It is these lower layers—physical, data link, and network—that provide the “railroad tracks” for the user data. They allow the data to ride across the network, such as when sending an e-mail or surfing the Internet.
The physical layer moves the bit stream (signal) from one point to another across a carrier, such as a network cable, originating from the transmitter (device sending the signal) and terminating at the receiver (device receiving the signal). For example, when you have a telephone ...
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