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TCP/IP Layering Model

5 Layers of TCP/IP

Layer 5. Application Layer
    Application layer is where applications requiring network communications live. Examples of these applications include email clients and web browsers. These applications use the Transport Layer to send requests to connect to remote hosts.

Layer 4. Transport Layer
    Transport layer establishes the connection between applications running on different hosts. It uses TCP for reliable connections and UDP for fast connections. It keeps track of the processes running in the applications above it by assigning port numbers to them and uses the Network layer to access the TCP/IP network.

Layer 3. Network Layer
    Network layer is responsible for creating the packets that move across the network. It uses IP addresses to identify the packet’s source and destination.

Layer 2. Data Link layer
    Data Link layer uses a Media Access Controller (MAC) to generate the frames that will be transmitted. As the name suggests, the MAC controls the physical transmission media. The wireless transmission media used for Wi-Fi® or 802.11 has different requirements from the wired transmission media used for Ethernet or 802.3, and therefore needs a different MAC and PHY. Note the upper layer software is not aware of or affected by the physical interface.

Layer 1. Physical layer
    It sends and receives signals on the physical wire or antenna to transmit the bits found in frames. At the end of any network interface, there is a PHY.

Comparing the TCP/IP model with the OSI model

The first thing we're going to take a look at are the similarities between these two models which are:

  1. Architecture
    Both the TCP/IP and OSI reference models have relatively similar looking architectures which are composed of multiple layers.

  2. Standards
    Both of these layers have defined and clear standards of networking, and they also provide the framework used for implementing the standards and devices. The clearness is due to the fact that these standards are already pre defined and these models are only referencing them when needed.

  3. Compatibility
    Both models are designed in a way that is aplicable to devices and components by other companies/manufacturers. There isnt a need to completely overhaul a design of a machine because of the already very compatible way the networks are set up.

  4. Layers
    Both models share a common layer known as the 'Application Layer'. However, the details and functions might be different for each layer, this of course is dependent on each models specific needs. Also many of the layers described in both models can very well be compared to each other because of how similar/comparible some of their functions might be. Both models also adopt a general idea that each layer has its own distinct functionality from the rest of the layers, what that means is that each layer has a job that most likely is unique to itself and within the structure of said model.

  5. Data
    Data in both models are simplified and divided into packets so that each specific piece of data in that packet can take its own individual route from its original source to wherever it needs to go.

  6. Troubleshooting
    Both TCP/IP models and OSI models have the same idea in regards to trouble shooting. That idea consists of breaking down and simplifying complex functions into relatively easier to understand components.

Next up are the very important key differences between the two seperate models which are:

  1. As we know, both models have a Architecture based solely on layers, the main difference is in the number of them for each model. The OSI model has 7 layers meanwhile the TCP/IP model only has 4 layers.

  2. The TCP/IP follows a vertical approach which means that each layer is traversed during the travelling of data and thus accesing all of their functionalities, only after passing all of these layers is the message sent, hence it is called the vertical approach. Meanwhile, the OSI model applies a horizontal approach which just means that there are no intermediate layers between the transport layers and above. This means that layers communicate directly with each other which is why its considered the horizontal approach

  3. OSI model is developed by ISO (International Standard Organization), whereas TCP Model is developed by ARPANET (Advanced Research Project Agency Network).

  4. TCP/IP is more of a standard set of protocols that are used to help the process of connecting various hosts over a network. It lays out the standards on which the internet was built/developed. OSI on the other hand is mostly a generic protocol independent standard that has the main purpose of creating a gateway in which communication between the end user and network can be established. TCP/IP is basically a somewhat simplified version of an OSI model.

  5. The OSI model was developed before the development of its protocols. On the other hand, TCPI/IP developed the protocols first and only after it was completed did they develop the model.

  6. OSI model has a clear definition of all the services, interfaces and protocols and makes clear distinction between them. It is protocol independent. In TCP/IP, services, interfaces and protocols are not clearly separated. It is also protocol dependent.

  7. Because of the dependence on them, protocols when needed to be replaced in TCP/IP cannot be done very easily at all. Meanwhile, an OSI model has protocols that are much better covered and far easier to replace thus it can handle change/evolution in technology much better than the TCP/IP model can.

  8. The network layer in TCP/IP is considered Connection less, meanwhile the network layer in OSI is considered both Connection oriented and Connection less.

  9. Delivery of data packets is only guaranteed in the OSI models. Even though the transport layer in TCP/IP is still a very much reliable and trustworthy model, it 100% does not provide the same security and guarantee when it comes to the delivery of packets.

References:

https://www.javatpoint.com/osi-vs-tcp-ip
https://www.studytonight.com/computer-networks/comparison-osi-tcp-model
https://www.omnisecu.com/tcpip/comparison-between-tcpip-and-osi-models.php
https://www.360training.com/blog/comparing-osi-tcpip-models
https://www.tutorialspoint.com/OSI-vs-TCP-IP-Reference-Model#:~:text=TCP%2FIP%20does%20not%20have,is%20a%20more%20practical%20model.
https://www.guru99.com/difference-tcp-ip-vs-osi-model.html#:~:text=OSI%20refers%20to%20Open%20Systems,both%20connection%2Doriented%20and%20connectionless.
https://microchipdeveloper.com/tcpip:tcp-ip-data-link-layer-layer-2
https://microchipdeveloper.com/tcpip:tcp-ip-physical-layer-layer-1