What are the Protocols? 


What are the Protocols? 

What are the protocols? In this article, every question about the Protocols will be answered. Also, you will learn its important functions.

The definition of the Protocols

The entities of the network that want to exchange information must shake hands, negotiate some procedures, rules, etc, together we must "speak the same language". The conversational rule set is called protocols. The main components of a protocol include:

  • Syntax: data format, encryption method and signal levels.
  • Semantics: control information, flow control and errors handling.

Information exchange between two entities can be direct or indirect. In two point-to-point connection systems, entities can exchange information directly without the intervention of intermediate entities. In the broadcast structure, two entities exchanging data must be through intermediate entities. It is more complicated when entities that do not share on the same switching network are connected indirectly across multiple subnets.

Protocols’ functions


In the information exchange process, data packets are added to some control information including source and destination address, errors detection code, protocol control, etc. Information addition to data packets is called encapsulation. The receiver will do the reverse, control information will be removed when the packet is transferred from the lower floor to the upper layer.

Split and merge

The communication network only accepts the default data packets sizes. The protocols in the lower level need to break data into specific sizes. This process is called split. In contrast to the split in the transmitting is the merge of the receiving. Data split ensuring the order to the destination is important. Data packets exchanged between two entities is known as PDU protocol (Protocol Data Link).

Connection control

Information exchange between two entities can be performed under two methods: Connection-Oriented and Connectionless. Connectionless doesn’t require high reliability,  service qualities, and confirmation. In contract, Connection-Oriented requires high reliability, service qualities, and confirmation. Before two entities exchange information, a connection is established and after the exchange, the connection is released.


PDU packets can independently travel between different paths when arriving at the destination may not be in the same order as when transmitted. In the Connection-Oriented, packets must have the monitor requirement. Each PDU has a unique set code and is resigned sequentially. The receiving entities will restore the order of the packets as the order of transmitting.

Flow control

Flow control refers to the receiving entity's ability to receive packets and the amount or speed of data transmitted by the transmitting entity so that the receiving is not overwhelmed, ensuring the highest speed. A simple form of flow control is the Stop-and Wait procedure, in which each transmitted PDU needs to be confirmed before transmitting the next packet. Highly reliable when transmitting a certain amount of data without confirmation. The sliding window technique is an example of this mechanism. Flow control is an important function that must be performed in some protocols.

Error control

Error control is the necessary technique to protect data from loss and damage in the information exchange process. Detection and fix include errors detection on a frame basic check and retransmitting PDU in the event of errors. If an acknowledgement entity PDU fails, the packet will normally have to be replayed.


The protocol entities have parameters for the state variables and definition of the state, which are the window size parameters, associated parameters, and a time value. Two communication entities in a protocol need to be in the same state at the same time. For example, the same initialization, checkpoint and cancel state, is called synchronization. Synchronization is difficult if one entity can only determine the state of the other when it receives packets. The packets do not arrive immediately but take a while to travel from source to destination, and PDU packets can also be lost during transmission.


Two entities that can communicate with each other, need to be identifiable. In the broadcast network, the entities must identify their identifier in the packet. In switched networks, the network needs to identify the target entity to route the data before establishing a connection.

In conclusion, a network protocol (protocol) is a protocol or convention of a computer. Since then the exchange of information will be simpler and follow certain principles. We hope through this article you will understand more about the concept of a protocol.

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