How many layers does the internet have

DoD layer model

In computer and network technology, layer models have become established to break down complex processes into individual steps. Each step or each task is represented as a layer in a layer model on top of one another.

The DoD layer model is the layer model on which the Internet is based. Since the Internet is a development of the American Department of Defense, the name of the layer model was derived from the English name Department-of-Defense (DoD).
A total of 4 layers are defined in the DoD layer model, which can be compared with the OSI layer model (ISO standard). One can say that the DoD layer model is a simplified variant of the OSI layer model.

DoD layer modelOSI layer model
4.Application layer
Application layer
Application layer7.
Presentation layer6.
Communication layer5.
3.Transport layer
Transport Layer
Transport layer4.
2.Internet layer
Internet Layer
Network layer3.
1.Network access layer
Network Access Layer
Data link layer2.
Physical layer1.

4. Application layer

The applications and protocols that communicate with each other over the Internet are defined in the application layer. These include HTTP, FTP, SMTP, NNTP and many more.

3. Transport Layer - Transport Layer

The transport layer serves as the control protocol for the data flow between the application and the Internet layer. The protocols TCP and UDP work here.

2. Internet Layer - Internet Layer

On the Internet layer, the individual data packets are given an address and their size is adapted to the transmission system (fragmentation). The data packets are usually transmitted with IP. Several control protocols that are closely linked to IP are active on this layer.

1. Network Access Layer

This layer is the lowest layer of the DoD layer model and represents the access to the network. In local networks this is, for example, Ethernet or WLAN.

DoD vs. OSI

When it comes to the description of protocols in the Internet and network technology, the DoD and OSI layer models are optionally used. Although the Internet and thus all networks are based on the DoD layer model, reference is regularly made to the OSI layer model.
The OSI layer model was only developed a few years after the DoD layer model. However, it is based on this to be backwards compatible. The direct comparison shows a certain similarity. The OSI layer model is, however, much more finely structured and more flexible. The OSI layer model allows individual layers to be combined or removed.
In the case of Ethernet and other network access layers, two or even more layers are often required for their description. In the DoD layer model, the protocols are firmly linked to the layers and therefore do not allow any adaptation. The network protocols TCP / IP are firmly anchored in the DoD layer model and cannot be replaced. There are hardly any alternatives in the usual network structures. Only the applications and transmission media on DoD layers 1 and 4 can be exchanged as required.

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