The TCP/IP protocol suite is named for two of its most important protocols Transmission control protocol (TCP) and Internet protocol (IP). The TCP/IP protocol suite establishes the technical foundation of the Internet. The Department of Defense (DoD) developed TCP/IP to ensure and preserve date integrity. TCP/IP model contains a large number of protocols, which helps one computer to communicate with another. Description of each of these protocols is documented by Request for comments (RFC) and it is approved by Internet Engineering Task force (IETF). This model is a condensed version of the OSI model and contains only four layers. They are Application layer, Host-to-Host layer, Internet layer and Network access layer. Each of these layrerwill be discussed in detail in this lesson.
Like other networking models, TCP/IP divides the functions of communication protocols into different layers. Most description of TCP/IP defines three to five levels in the protocol architecture. The four level model is based on the three layers(Application, Transport and Network Access) as defined in the DOD protocol model with the addition of Internet layer. The protocols at the internet and transport later: Internet protocol (IP), Transmission control protocol (TCP) and User Datagram Protocol (UDP) is usually called as “core” of the suite which supports to perform a variety of functions at each of the TCP/IP model layer. The layers in TCP/IP Architectural Model are shown in figure.
The DoD model is basically a condensed version of the OSI model- it’s composed of four, instead of seven, layers:
Figure shows a comparison of the DoD model ( TCP/IP Mode ) and the OSI reference model. As you can see, the two are similar in concept, but each has a different number of layers with different names.
TCP/IP Model and OSI model are quite similar in nature. Data is passed down the stack when it is being sent to the network and up the stack when it is received from the network. Every layer uses control information to keep addressing and other information that is needed by the protocol to deliver the data. These control information is called as header or trailer. Each layer upon receiving the data from the previous layer adds its own header in front of the information. This process of adding control information is known as Data encapsulation. When the data is received from the network, opposite procedure happens. At each layer the headers are the headers are stripped off and discarded before passing it to next layer. The process of removing header or trailer from the data is known as Decapsulation.
Each layer in TCP/IP model has its own data structure, but a layer will not know the data structure used by the layer below and above it.
TCP/IP protocol Architecture
Like other networking models, TCP/IP divides the functions of communication protocols into different layers. Most description of TCP/IP defines three to five levels in the protocol architecture. The four level model is based on the three layers(Application, Transport and Network Access) as defined in the DOD protocol model with the addition of Internet layer. The protocols at the internet and transport later: Internet protocol (IP), Transmission control protocol (TCP) and User Datagram Protocol (UDP) is usually called as “core” of the suite which supports to perform a variety of functions at each of the TCP/IP model layer. The layers in TCP/IP Architectural Model are shown in figure.
TCP/IP and the DoD Model
The DoD model is basically a condensed version of the OSI model- it’s composed of four, instead of seven, layers:
- Process/Application layer
- Host-to-Host layer
- Internet layer
- Network Access
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| OSI-TCP/IP Model |
Figure shows a comparison of the DoD model ( TCP/IP Mode ) and the OSI reference model. As you can see, the two are similar in concept, but each has a different number of layers with different names.
How protocol stack works
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| Two Internet hosts connected via two routers and the corresponding layers used at each hop. |
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| Encapsulation of application data descending through the TCP/IP layers |
Each layer in TCP/IP model has its own data structure, but a layer will not know the data structure used by the layer below and above it.
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