There are two versions of the TCP/IP layers model. The original model has four layers whereas the new model has five layers. The new TCP/IP model breaks the physical link layer into two separate layers and renames the internet layer to the network layer.
The original TCP/IP layers model
The original TCP/IP model is described in RFC 1122. It describes how computers communicate in a network. It defines all standards, protocols, references, and specifications computers require to communicate. To define a standard or a protocol, it uses documents called Requests for Comments (RFC).
It does not define the standards or protocols that have been already defined by other vendor consortiums or standards bodies. If a protocol or a standard has already been defined, it provides a reference to that protocol to avoid repeating work. For example, it does not define Ethernet LANs. Because Ethernet LANs were already defined by IEEE. So, instead of defining them again in RFCs, it provides a reference to them.
The original TCP/IP model divides the communication process into four layers. These layers: application, transport, internet, and link. The application and transport layers focus on the applications that send and receive data. The internet layer focuses on delivering data over the entire path from the sending device to the receiving device. The link layer focuses on how to transmit data over physical links.
The modern TCP/IP layers model
The modern TCP/IP layers model is an updated version of the original TCP/IP model. In this model, the application and transport layers are identical to the application layer and transport layer of the old TCP/IP layer model. The internet layer's name is changed to the network layer. It breaks the link layer into two layers: the physical layer and the data link layer. It describes physical media and its standard in the physical layer and the protocols that convert data into signals in the data link layer.
Similarities between the old TCP/IP model and the new TCP/IP model
- Both models describe how computers communicate in a network.
- Both models break the communication process into layers.
- Both models use RFCs to define standards and protocols.
- Both models provide reference to other models for the protocols and standards defined by them.
- The application layer and transport layer are the same in both models.
Differences between the old TCP/IP model and the new TCP/IP model
- The old TCP/IP model uses four layers to define the standards and protocols for the communication process. The new TCP/IP model uses five layers for the same thing.
- The old model uses the single link layer to describe protocols that convert data into electric signals and radio waves and specifications for media that carry them.
- The new model uses the physical layer to describe specifications for the media that carry signals and the data link layer to describe the protocols that convert data into signals.
- There is also a naming difference between both models. The name of the internet layer is the network layer in the new model.
