Windows 2008 Server and OSI Model of Networking

The OSI Model Of Networking

Windows Server 2008 Review and Guide

NOTE The OSI model is useful for describing networking and for relating its various components. It

does not necessarily represent Windows Server 2008 or any other networking implementation, but it

is a widely known and accepted reference.

 

Physical layer Defines the physical specifications, such as voltages

and timing, to make the network interface function as intended. These

specifications are implemented in networking hardware.

 

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Data Link layer Defines the addressing of frames and the sending and

receiving of frames between two linked computers. After passing a frame to the is not received, the Data Link layer resends the first frame. The Data Link layer

provides point-to-point linkage between itself and the receiving computer

by using physical addresses. The physical address at the Data Link layer is

called the media access control (MAC) address. The Data Link specifications are

implemented in a combination of hardware and dedicated networking software.

 

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Network layer Defines the packaging of packets into frames and the logical

addressing (as opposed to the physical addressing used in the Data Link

layer) necessary to provide internetwork routing through multiple, connected

networks. Packets, which may be larger or smaller than frames, are broken up

or combined to create a frame in the sending computer, and are reassembled

or disassembled in the receiving computer to reproduce the original packets.

The Network layer's internetworking commonly uses the Internet Protocol

(IP) addressing to identify where frames should be sent. The Network layer

specifications are implemented in dedicated networking software.

 

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Transport layer Defines the division of a message into packets, the

identification of the packets, and the control of the packet transmission to know

whether the packets are being sent and received correctly, and if not, to pause

and resend a transmission. The Transport layer creates, regulates, and terminates

a flow of packets by using a virtual circuit between the sending and receiving

computers (the flow is still down through the other layers, across the connection,

and up the other side, but it occurs as if the two Transport layers were directly

talking to each other). The Transport layer commonly uses the Transmission

Control Protocol (TCP) to start, regulate, and terminate the flow of packets. The

Transport layer specifications are implemented in networking-related operating

system (OS) software, such as Windows Server 2008, using networking protocols.

 

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Session layer Defines the dialog between computers so that they know both

when to start and stop transmission, creating a session, and when to repeat a

session if it is not correctly received. The Session layer also handles security-related

issues and has its roots in the mainframe/terminal timesharing environment. The

Session layer specifications are implemented in network-related OS software.

 

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Presentation layer Defines the encoding of information so that it is easily

and securely transmitted and read by the receiving computer. This includes the

conversion of character, graphic, audio, and video information into common

data representation, the encryption and compression of information, and the

return of the information to its native form upon receipt. The Presentation layer

specifications are implemented in OS software.

 

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Application layer Defines the mechanism by which applications access the

network to send and receive information. This includes the two-way handling

of information, as well as the identifying, locating, and determining of the

availability of the partner for an information exchange. The Application layer

specifications are implemented in OS and application software.