The TCP/IP protocol uses four distinct layers: the network access layer, the datalink layer, the transport layer, and the internet/application layer. Each layer has its own data structure and terminology. These layers perform different functions and are ordered from application layer to network access layer. Let’s look at each of them in turn. The Internet layer manages and controls the flow of data. The Transport Layer provides a reliable data connection between two devices. It divides data into packets and acknowledges packets from the other device.
The Internet Layer is the second layer in the TCP/IP model. This layer is located between the Transport Layer and Network Access Layer. IP datagrams are packets that contain source and destination addresses. The Internet Layer forwards data between hosts and across networks. The Internet layer also routes messages. The Internet layer is responsible for the routing of IP datagrams. While each layer has its own unique role in the TCP/IP model, each layer performs a different function.
The Data Link Layer (DL) is responsible for delivering data packets across the physical network. TCP/IP rarely creates protocols for the Data Link Layer, and most RFCs related to this layer discuss how IP utilizes existing data link protocols. The Physical Layer is concerned with defining the characteristics of the hardware that must carry the transmission signal. The Physical Layer also defines the standards for local area network wiring. TCP/IP does not define any of these physical standards.
TCP also performs end-to-end communication. It does this by breaking the data into packets, each with a header. Every segment must be inspected and verified by the source end before the transmission can take place. Next, TCP forwards data to the Internet layer. There, data packets are translated into IP addresses and sent to the destination network. Once the data packets arrive, the process of data transfer begins.
The Application Layer (AL) combines the functionality of the other three layers. It serves as the interface between the application and the network. It is responsible for presenting data to the user. These protocols include HTTP, FTP, and HTTPS. When properly configured, these layers are essential to internet connectivity. When the data is on the network, it is transferred from the server to the client. A good example of an Application Layer protocol is HTTPS.
The IP layer is the highest layer of the Internet. It is composed of IPv4 and IPv6. IPv4 is the most common version of IP and IPv6 is an enhanced version of IP. IPv6 is an IP standard with greatly expanded addressing capacity and a different address structure. Neither is fully interoperable with IPv4 and is not widely used in operational commercial networks.
The Transport Layer is the third layer of the TCP/IP model. It is situated between the Internet layer and Application layer. The Transport Layer permits conversation between hosts. It also determines the level of service and status of the connection. The two main protocols used at this layer are the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).