The Osi and Tcp/ip Models:

Today I am going to compare and explain each of the layers in both the OSI and TCP/IP models. First I will be talking about the OSI model. The OSI (Open systems interconnection model) model has 7 layers from the Physical layer to the Application layer. The first layer the physical layer involves the movement of data though a network. This layer will also allow hardware to send and receive data via a network carrier (e.g. three, EE). A Device that will connect to this layer will be a hub. The second layer the Data link layer is to create links across the network, this action is done my gathering information and sending data in the form of frames. Devise on this layer would include bridges and switches. Layer three is the Network layer, this layer is used for creating the addresses and the route for the data to travel in. this then ensures that the data gets sent to the right place. An example of this layer would be IP addresses. On this layer the device that will be connected is the Router.

The next layer the transport layer is designed to manage the packets of data being sent and then make sure they get delivered to the correct location. This layer will also check for any damaged data, which have may occur during transport. The fifth layer, which is the session layer, has the job of handing conversations. This will involve the set and ending of conversations. This also includes connecting and even reconnecting after the connection was lost or interrupted. The sixth layer the presentation layer is most often part of the operating system. Its job is to convert the incoming and outgoing data on the network into a readable format. The last layer of the OSI model is the Application layer this layer is used to identify partners and this allows the data that is sent to be open and displayed to the user. The devices that would connect to this layer would be PCs, servers, and phones and also hosts.

The TCP/IP (Transmission control protocol/internet protocols) model only has 4 layers from the Network access to the Applications layer. The TCP/IP model is built into every computer and its needed to be able to access the Internet. The bottom layer, which is the network access layer, is where the details of how the information is sent though the network. For example, how the data bits are sent, this layer also deals with the hardware devices such as the fibre optic or Ethernet wires. The next layer is the IP layer, this layer is used to convert the data being sent into IP datagrams, and this will then allow the data to be sent on across the network. The next layer up is the TCP layer this layer has the purpose of allowing devices to connect and host conversations and share data through the network. The last layer, the application layer is at the top of the model and this layer is designed to define the TCP/IP protocols and is also determine how each program running on the network are being hosted. An example of this could be the DNS (domain naming system).

Next I am going to talk about the differences between each model and I will explain why some layers are missing from the TCP/IP layer. First I will talk about the missing layers on the TCP/IP model. The missing layers are not missing but they are combined into one layer, the presentation layer and the session layer of the OSI model have been combined together to create the application layer. This is also the case for the data link and physical layer, which are located in the network access layer on the TCP/IP model. This removing of layers makes the TCP/IP model looks less complicated but in reality, both models have the same number of layers.

In conclusion, both of the models are important and without them data wouldn’t be able to be sent over a network or the Internet. Both the models also have many similarities and differences, For example one similarity between them is that of there structure, they are both layered and both contain a application layer. The application layer has the same job on both models, however each model uses different services depending on what model is being used. Another similar feature that both models have is that they both have similar transport and network layers; this will mean that any function performed though one of these layers will have the same effect on both models. My final similarity I will talk about is both models will assume that each packet sent will be switched or mixed up. This meaning that both layers will have extra information that will be sent with each packet to allow the data to be assembled correctly.

Both models also have many differences. For example the first difference I will talk about is the fact that the OSI model has 7 layers while the TCP/IP only has 4. However, this is because the TCP/IP model combines some layers together into one layer to make it shorter. Thus making it less complicated to understand. Another difference I will talk about is the fact that the TCP/IP model is considered more reliable. This is because the protocols are the standards to which the World Wide Web was built. But the OSI layer is only a guideline to help models be built around.