A network protocol is an established set of rules that determine how data is formatted, transmitted, and received between devices across networks. A network protocol is essentially a language that two devices can both understand in order to communicate with each other, regardless of internal process, infrastructure, or design disparities.
Network protocols are used for global communication, and neither local area networks (LAN) nor wide area networks (WAN) could function without using network protocols. Support for these protocols can be built into software, hardware, or both.
Network protocols break large-scale processes into small, specific tasks or functions across every level of the network. Each function must cooperate at each level in order to complete the large-scale process.
Network protocols are typically created according to an industry standard. Information technology organizations that have defined and published network protocols include:
While there are multiple protocols available, the majority of them are structurally based on the Open Systems Interconnection (OSI) model, known as the standard protocol model. The OSI model splits the communication process between two network devices and seven layers. A task or group of tasks is assigned to each layer. All layers are self contained, and tasks assigned to them are executed independently. From seven down to one, the OSI layers are as follows:
6. The presentation layer makes data understandable for the application layer and prepares it to be sent over the network.
5. The session layer manages sessions between clients and servers, initiating them and determining their duration.
4. The transport layer manages data packets as they are sent across a network and the correct amount of data so that the system is not overwhelmed.
3. The network layer properly directs data packet transmissions between routers and throughout the network.
The seven layers can be divided into two groups: upper layers (7,6, & 5) and lower layers (4,3,2, & 1). The upper layers deal with application issues, while the lower layers deal with data transport issues.
Common network protocols include: