Presentation layer is also called the translation layer. The session layer is responsible for the establishment of connection, maintenance of sessions and authentication. The transport layer also provides the acknowledgement of the successful data transmission and re-transmits the data if an error is found. It is responsible for the end-to-end delivery of the complete message. The data in the transport layer is referred to as segments. The transport layer provides services to the application layer and takes services from the network layer. The datagram is also composed of a header and data field. The basic unit of transfer is a datagram that is wrapped (encapsulated) in a frame. The network layer ensures the data transfer between two hosts located in different networks. The data link layer is divided into two sub layers:
When a packet arrives in a network, it is the responsibility of the data link layer to transmit it to the host using its MAC address. The main function of this layer is to make sure data transfer is error-free from one node to another, over the physical layer. The data link layer is responsible for the node-to-node delivery of the message. Physical circuits are created on the physical layer.
To put it differently, the physical layer describes the electric or optical signals used for communicating between two computers. The physical layer is responsible for activating the physical circuit between the data terminal equipment and data circuit-terminating equipment, communicating through it and then deactivating it. The following section briefly discusses each layer in the OSI model. The OSI model breaks the various aspects of a computer network into seven distinct layers, each depending on one another. The International Standardization Office (ISO) has standardized a system of network protocols called ISO OSI. Many of them have become out of date, so only a handful of the first thousand RFCs are still used today. RFCs are numbered from 1 onwards, and there are more than 4,500 RFCs today. The standards that are used for the internet are called requests for comment (RFC). As protocol is a set of standards and rules that has to be followed in order to accomplish a certain task, in the same way network protocol is a set of standards and rules that defines how a network communication should be done.
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