The Osi Model - D-Link DFL-1600 User Manual

Open System Interconnection (OSI) model defines a primary framework for
intercomputer communications, by categorizing different protocols for a
great variety of network applications into seven smaller, more manageable
layers. The model describes how data from an application in one computer
can be transferred through a network medium to an application in another
computer. The control of the data traffic is passed from one layer to the
next, starting at the application layer in one computer, proceeding to the
bottom layer, traversing over the medium to another computer and then
delivering up to the top of the hierarchy. Each layer handles a certain set of
protocols, so that the tasks for achieving an application can be distributed
to different layers to be implemented independently.
Table 2.1 shows the definition of the 7 layers. The basic functions and
common protocols involved in each layer are explained below.
Application Layer
– defines the user interface that supports applications directly.
Protocols: HTTP, FTP, DNS, SMTP, Telnet, SNMP, etc.
Presentation Layer
– translates the various applications to uniform network formats that
the rest of the layers can understand.
Session Layer
– establishes, maintains and terminates sessions across the network.
Protocols: NetBIOS, RPC, etc.
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The OSI Model

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