Nt1310 Unit 7 Layers Analysis

The 7 layers can be split logically into two subgroups. Layers 7 thru 4 focus on the end to end communication of data source and destinations. Layers 3 thru 1 are provide consistent communication between the network devices. An easier way of looking at the OSI model is dividing the upper layers (7, 6, 5) from the lower layers (4, 3, 2, 1). The upper layers deal with application issues and are implemented only in software. The highest layer, the application layer, is the closest to the end user. The lower layers are responsible for the transportation of the data. The physical layer and the data link layer are implemented in hardware and software. The lowest layer, the physical layer, is closest to the physical network medium (the wires, for example) and is responsible for placing data on the medium.
The following is a top-down
At the destination this layer is responsible for combining the packets into their original state. This layer also checks to see if the layers are in the right order when received and not in duplicated form. If there is an error in one of the packets there is a request for that packet's retransmission. There are two protocols that sit at this layer. First, the TCP protocol connects the sender and the receiver using a socket which is determined by the IP address and port number. TCP keeps track of the packet delivery order and which ones need to be resent. UDP on the other hand is a connectionless communication and does not guarantee packet delivery between sender and receiver. Because it is connectionless the sender sends the data into the network with an IP address of the receiver and hopes it makes it to its destination. Since there is not a way of asking the sender to retransmit because of an error there is little error protection if