The lower layer encapsulates the higher layers data between a header. Like with the tcpip layers, each osi layer asks for services from the next lower layer. The data is encapsulated with protocol information at each osi reference model layer when a host transmits data to another device across a network. Encapsulation and decapsulation are two terms related to passing data through each layer. In our case the application needs to add encryption to that data.
Osi layers when osi was in active development in the 1980s and 1990s, in some cases. Access points are bridges that bridge traffic between mobile stations and other devices on the. Although it is the older model, we still use the osi layers to reference our networks in todays. The key difference between encapsulation and decapsulation is that, in encapsulation, the data moves from upper layer to the lower layer, and each layer. In other cases, the osi committees did not create new. We currently have a asa5516 firewall and our core switch is a cisco 4500x. The computer in the above picture needs to send some data to another computer. Data encapsulation in the osi model ccna geek university. Osi reference model the open systems interconnection osi model was developed by the international organization for standardization iso, and formalized in 1984. Each layer communicates with its neighbor layer on. Data goes through the layers of data communication.
Data encapsulation in the osi model utilize windows. The osi network architecture model is the older of the two models. For the sake of clarity, we will be using the tcpip model to demonstrate encapsulation, as compared to the osi model. The data is encapsulated with protocol information at each osi reference model layer. The open systems interconnection osi model was developed by the international organization for standardization iso, and formalized in 1984. The picture below is an example of a simple data transfer between 2 computers and shows how the data is encapsulated and decapsulated. Segments layer 4 transport layer encapsulation which encapsulates application layer and data into a segment header, and uses source and destination port numbers for tcp or udp protocols. When we discuss data encapsulation with the tcp ip model, we use what are called segments, packets and frames. Data flow occurs when two devices are connected in a network with some kind of shared transmission medium. If you are still struggling with grasping concepts of the tcpip model you may wish to view the previous section once more. Data encapsulation in the osi model in the previous lesson we have learned that the term encapsulation describes the process of putting headers and sometimes trailers around some data. Tcpip is the new network model that is a replacement for osi model. It provided the first framework governing how information should be sent across a network. It tells the computer what its supposed to do when data needs to be sent or when data is received.
It divides the communications processes into seven layers. You must keep in mind that the osi model is a guideline. Understanding data encapsulation the sending and receiving of data from a source device to the destination device is possible with the help of networking protocols when data encapsulation is used. The osi model is just a reference model, so manufacturers have been free to create protocols and products that combine functions of one or more layers. The 4500x is doing all our internal routing between vlans and has a default gateway pointing to the asa for outgoing traffic. Encapsulation starts from the uppermost layer a lowest layer decapsulation star. An application running on the source device creates some kind of data.
In networking model, the terms encapsulation and deencapsulation refer to a process in which protocol information is added to the data and removed from the data when it passes through the layers. Weve also already seen that using osi terminology, lower layers are said to provide services to the layers immediately above them. This article is an introduction to the osi model for networking students. Difference between encapsulation and decapsulation. The osi model describes an idealized network communications protocol family. Each layer both performs specific functions to support the layers above it and offers services to the layers below it. In order to make it easier for most, there is a movie file available which will show your exactly what we are about to analyse.