Communication Protocol is a method so that a computer can connect with other computers. In the past, vendors had different protocol systems or communication between computers, so communication between computers of different vendors was difficult. Therefore, ISO (International Organization for Standardizaton) sets a standard for communicating between computers, so that communication between different vendors can be done.
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OSI layer
In 1977, ISO realized the urgent need for a method to equalize the connection method between computers and so decided to form a new subcommittee (SC16). The first SC16 meeting was held in March 1978. After 18 months of discussion, an ISO architectural model known as the OSI Reference Model was created [4]. The OSI layer is made up of more than 100 experts from several countries and international organizations.
OSI Layer Image
Referring to the picture above, the OSI reference model has 7 layers. Each layer has its own function. The layer closest to the user is the application layer. The OSI layer can be divided into 2 parts, namely the upper case and lower case. The application, presentation, and session layers are the upper case, while the rest are the lower case. This division is based on because when the data packet is in the upper case there are no additions or changes to the data packet. Changes and additions to data packets start when the data is in the transport layer. The following is an explanation of the function of each layer:
1. Physical layer
The physical layer is the lowest layer of the OSI layer. This layer is combined into parts that combine the physical components of a computer. This layer functions to transmit data in the form of electro-magnetic signals. In addition, it functions to connect one computer to another.
2. The Data Layer
The data layer is responsible for turning the data bits sent from the network layer into frames and controlling errors sent by the physical layer.
3. Network layer
The delivery of data from source to destination is the responsibility of the network layer. If a connection uses the same address, usually there is no need for the network layer, on the other hand, if the address is different, the network layer has an important role in sending it to its destination, starting with IP addressing and routing.
4. Transport layer
Computers sometimes undergo several applications at one time, for that the transport layer is in charge of sharing data into several sequential segments so that when the packet is received it can be arranged according to the order of the segments that have been given.
5. The Session layer
Synchronization between connections is a function of the session layer.
6. Presentation Layers
Before the data is transmitted to the network, a data packet will be translated so that the data packet is compatible with the format in the application layer. This layer is also in charge of encrypting data so that the data becomes private and is not easily seen by other users.
7. Application Layer
As an interface between the user and the computer so that the user can send the desired data packet to the destination and process the data.
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TCP / IP layer (Transmisson Control Protocol / Internet Protocol)
TCP / IP is a communication protocol that is responsible for communicating between two host computers. TCP / IP was first developed by Darpa, and is the most popular protocol to date. The simplicity that TCP / IP has is the broad standardization of the protocol and is a hot topic in the RFC (Request for Comment).
TCP / IP Layer Image
Compared to the OSI layer which has 7 layers, TCP / IP only has 4 layers. Even though it only has 4 layers, TCP / IP is compatible with OSI. TCP / IP has protocols that have their respective duties.
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