The application layer is at the top of the Five Layer Internet Architecture. It is responsible for handling high-level protocols and allows the user to interact with the application. The application layer protocols are serviced by the transport layer upon which it is built.
The transport layer is responsible for sending data end-to-end across a network while ensuring reliability, flow control, and correction of data. It acts as the middleman between the application layer and the transport layer, connecting the applications on different hosts. It uses TCP for reliable connections with mechanisms to ensure packets of data arrive in order and without corruption. On the other hand, UDP provides unreliable transport but faster communication with less overhead. The transport layer also keeps track of the processes running in the applications above it by assigning a port number to them and using the Network Layer to access the TCP/IP network.
The network layer is responsible for creating the packet that moves across the network. With the help of the IP address, the network layer identifies the source and destination of each packet. It adds a header, including the source and destination IP Address, to generate the packet. The packet is routed across the different networks to the correct destination via the network layer. Once at the required network, the packet is serviced by the link layer.
The link layer is responsible for creating the frames that move across the network. These frames encapsulate the packets and use MAC Addresses to identify the source and destination. The link layer adds a header containing the MAC Addresses information to create a frame. The frame is then sent to physical layer to transmit the bits.
The physical layer is on the bottom of the network architecture. It is used to send bits from one computer to another. The physical layer converts the data in electronic pulses. This data is then represented in binary form and sent to wireless or wired devices.
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