Moduel B Assignment #4

OSI means Open Systems Interconnection. It is a definition of network framing in seven layers. OSI control is passed from layer to layer. It starts at the applcation layer (layer 7) and works its way down to the physical layer (layer 1). After going from one layer to the other OSI starts going from channel to channel and then back up the layers.

Layer 7 is known as the application layer. It supports the application and the end-user processes. All the things in this layer are application-specific. This layer provides application services used in the transferring on files, e-mails, and other things the network software used. user authentication and privacy are considered for this particular layer. Another part of this layer are the tiered application architectures.

Layer 6 is known as the presentaion layer also known as the syntax layer. It provides independence from the differences in the data representation. This happens by translating from application to the network format, and the other way around. Also this particular layer formats data to be sent across networks, which provides freedom from compatibility problems that could arise.

Layer 5 is known as the session layer. It establishes, manages, and terminates the connections between applications. This layer sets-up, corrdinates, and terminates any conversation, exchanges and dialogues that might have happened between the applications. Also in this layer session and connection corrdination are delt with.

Layer 4 is known as the transport layer. In this layer the transparent layer or data between the systems are provided. This layer makes sure there is a complete data transfer between the systems.

Layer 3 is known as the network layer. In this layer there is the switching and routing of technologies. It creates logical paths that allows transmittion of data from node to node. Other functions of this layer are the routing and forwarding, addressing, internetworking, error handleing, and congestion control/ packet sequencing.

Layer 2 is known as the data link layer. All the data packets that have been sent to a system are encoded and decoded into bits. It is divided into two different sublayers: The Media Access Control- the sublayer that controls how a computer will gain access to a network's data and how is can get permission to tansmit that data. The Logical Link Layer- the sublayer that controls the flow control and error checking of a system's network.

The final layer is layer 1 which is known as the physical layer. In this layer there is the conveying of the bit stream (electrical impules, light/radio signals). This happens through the network at a electrical or mechanical level. This layer provides the hardware of sending and recieving of data by use of a carrier. Some examples of protocols with the physical layer compenents are: Fast Ethernet, RS232 and ATM.

Ethernet is relevent to OSI by how it defines a number of wiring/ signaling standards from the physical layer(Layer1). This happens by the means of a network access at the MAC/ Data Link Layers (Layer 2), also through a common address format.


Bibliography

http://en.wikipedia.org/Ethernet
http://en.wikipedia.org/wiki/Open_Systems_Interconnection
http://www.webopedia.com/quick_ref/OSI_Layers.asp