It 244 Network Security

Network Security

J. Adam Underwood

Intro to IT Security/IT 244

August 12, 2010

Network Security

In the early 1980’s the International Standards Organization (ISO) developed the Open System Interconnection (OSI) Reference Model for network communications [ (Merkow & Breithaupt, 2006) ]. The OSI reference model was designed to promote interoperability of network devices. The ISO wanted to make sure that parts from different manufacturers would be able to communicate with other parts from other manufacturers. Out of this the ISO came up with the seven layers of the OSI reference model that each manufacturer would have to adhere to.

The seven layers that they came up with are in a top-down format and include: application, presentation, session, transport, network, data link, and physical layers. To explain these in more detail we shall start with the top layer, the application layer, and work down to the final layer which is the physical layer.

The application layer is most directly related to computer use. This layer provides the services such as file transfer, resource allocation, and the verification and identification of computer availability. E-mail, the internet, and discussion groups are all programs that are used by this layer of the OSI model.

Layer six is the presentation layer. This layer is responsible for translating and presenting information to the application layer. When viewing a photo, video, and/or listening to music this is the layer that is doing the work. The presentation layer is also responsible for data encryption and decryption.

Layer five is known as the session layer. The session layer makes contact with hosts computers, establishes communication links, and recovers and restarts the system. This layer also uses formatting routines when using drop down boxes on various web pages.

Layer four contains the transport layer of the OSI model. This level ensures that the information is coming and going from the location that...