Write a Memorandum That Explains What Type of Security Is Associated with Each Level of the Open Systems Interconnect (osi) Model.

Lucy Jebian

Network and Telecommunications II - NTC 410

Professor Jeffrey Edwards

Week 4 Memo - Security and the OSI Model

May 6, 2006

Write a memorandum that explains what type of security is associated with each level of the Open Systems Interconnect (OSI) Model.

The International Standards Organization (ISO) philosophy is that different standards and open "layers" of the architecture should be handled(passive voice) by the different telecommunications functions. The International Standards Organization (ISO) Open Systems Interconnect (OSI) Reference Model below classifies seven layers of communications types, and the interfaces among them. (See Figure 1.) Each layer depends on the services provided by the layer below it, all the way down to the physical network hardware, such as the computer's network interface card, and the wires that connect the cards together. Basically, OSI divides the functions of a protocol into seven layers. This makes the reasoning easy to follow and the system much more reliable. The implementation of several OSI layers is often referred to as a Stack or a TCP/IP Stack. The layers are often referenced in descending order because layer 7 is the first layer that an end user sees.

Figure 1: The ISO/OSI Reference Model:

To apply security measures, two distinctive approaches have progressed overtime. One is the networked coupled security and the second is the application-coupled security. The networked coupled security favors the use of securing the networks infrastructure and the application-coupled security builds security into the applications themselves.

In a Network(network should not be capitalized) coupled scheme the main concentration is to make the network a trusted and secure subsystem. The main benefit to this approach is so that the applications can presume the data being transmitted(passive voice) is safe and that it comes from authorized users. If this approach is taken the main advantage is that applications do not have to be security aware and can be moved into a secure environment without modification.

On the other hand the Application Coupled Security argues that the application knows best what kind of security is required for that application. As a result, the application layer is the layer where the security access is controlled.

The OSI Model's Physical Layer of security applies to all physical devices in a

communications system and their availability in mission-critical situations. The OSI Model's Data Link Layer provides the security level