To understand networking is to understand the language of firewalls.A firewall is
used to segment resources and limit access between networks.Before we can really
focus on what a firewall does for us,we need to understand how networking works.
Today in most environments and on the Internet,the protocol suite TCP/IP
(Transmission Control Protocol/Internet Protocol) is used to transport data from
here to there.We will begin this chapter by looking at networking as a whole with a
focus on the Open System Interconnection (OSI) model.
The OSI Model
The OSI model was originally developed as a framework to build networking pro-
tocols ...
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