What are Data Link Protocols in Computer Network?

Protocols define a collection of rules or conventions for executing a definite function. It is a collection of the requirements that can manage the data link layer. The fundamental goals of computer broadcasting in a system environment are to transmit a limitless huge message from the source hub to the destination hub.

The major service of the Data Link Layer is to send the datagram across a single connection. In Data Link Layer, the datagram can be managed by various link layer protocols on multiple connections in a path. For example, the datagram is managed by Ethernet on the primary link, PPP on the second link.

Simplex Stop and Wait

An error-free transmission medium is considered. The source node recovers a packet from the network layer and encloses it into a frame to send. After sending, the source node stays for an acceptance from the destination node. After getting the exposure, the loop opens over repeatedly.

At the destination node, the device waits for a frame from the source destination. Then receiving a frame, it transfers the frame to the network layer and shares an affirmation for the frame to the source node. It then loops back to wait for the next frame, and the procedure continues till the end of the File frame is arrived.

It contains only one single frame at a time. Therefore, no sequence numbers are needed. The acceptance of the destination node address back to the source device is a null frame.

It is a data-link layer protocol that can be sending the data over noiseless channels. It supports unidirectional data transmission which represents that either sending or receiving of data will take place at a time. It supports a flow-control mechanism but does not support some error control structure.

The major drawback of this approach is that it is ineffective. It creates the transmission process moderately. In this approach a single frame carries from source to destination and a single acknowledgment carries from destination to source.

As a result, each frame transmitted and received uses the whole time required to traverse the connection. Further, if two devices are a distance apart, several times is wasted waiting for ACKs that generate an increase in total transmission time.

Positive Acknowledgement with Retransmission Protocol (PAR)

It is an advancement on the Stop and Waits protocol. The source device recovers a packet from the network layer. It can enclose it into a frame with a sequence number to share with the destination node. After communication, the source device tries to recover an acceptance from the physical layer.

Once an acceptance appears with the right sequence number, the following packet to transmit from the network layer is recovered. The sequence number to share the next packet is upgraded. In this case, the loop begins over.

If no frame is retrieved from the physical inside the particular time, the physical layer times out, or an acceptance with an inappropriate sequence number appears. In this method, the final frame address is retransmitted, and thus, the loop begins over.