Sliding Window And Stop - Wait Protocol For Flow Control In Data Link Layer? The 20 Detailed Answer

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Flow Control || Stop and Wait Protocol || Sliding Window Protocol || Data Link Layer Design Issues

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Flow Control || Stop and Wait Protocol || Sliding Window Protocol || Data Link Layer Design Issues

Images related to the topicFlow Control || Stop and Wait Protocol || Sliding Window Protocol || Data Link Layer Design Issues

Flow control is one of the most important aspects of the data link layer (DLL). It essentially determines the rate at which the sender must send packets before receiving an acknowledgment. Flow control refers to a set of techniques used to limit the amount of data a sender can send before waiting for an acknowledgment (ACK). The transmit rate of the transmitter may differ from the receive rate of the receiver. In this case, the data traffic must not increase compared to the sender (to avo further data traffic and congestion). Each receiving device has a limited speed at which incoming data can be processed and a limited amount of memory that must store incoming data. Therefore, flow control mainly helps to maintain the data transfer rate between sender and receiver. Each receiving device has a block of memory called a buffer that stores incoming data until it is processed. It is a set of programs that tell the sender how much data can be transferred before having to wait for the receiver to confirm (otherwise a data overflow will occur). To sum up, we can say that there should be a feedback mechanism to avo data overflow. Now let’s look at some of the methods implemented in the DLL for flow control:.

Stop-and-Wait Protocol in flow control of DLL

When data frames (arrival rate) arrive at the receiving site faster than they can handle, those frames must be stored until they are used. Often, sinks run out of disk space, especially when receiving data from multiple sources at the same time. This can eventually lead to dropped frames or denial of service. To avo the receiver being overwhelmed with frames, we need to somehow tell the sender to slow down. Here comes the feedback mechanism. This protocol is called a stop-wait protocol because the sender sends a frame, stops and waits until it gets an acknowledgment from the receiver (no problem moving forward), and then sends the next frame. The implementation of this scheme depends on the noise level of the channel. Let’s assume that the communication channel is noisy and may introduce errors into the data flowing through it. Channel noise can corrupt frames or lose them entirely. Let’s understand this in simple steps: the sender first sends a frame, then stops the transmission and waits for an acknowledgment from the receiver. If a positive acknowledgment is received (i.e. the receiver is ready to receive the next frame), go to step 1 above. If a negative acknowledgment (NACK) is received (the receiver is not ready to receive the next frame), wait for a positive acknowledgment (ACK) from the receiver. With this protocol, the sender waits for a positive acknowledgment before continuing with the next piece of data. When a frame is sent, a timer is set at the sender. If the sender times out, it resends the same frame. Hence, it is called a PAR (Positive Acknowledgment with Retransmission) or Automatic Repeat Request (ARQ) type of protocol. If a frame is severely damaged or lost, the sender will retransmit it. Since ACK (acknowledgement) frames can also be corrupted and lost, it also requires redundant bits and sequence numbers. ACK frames for this protocol usually have a sequence number field. Using this protocol, the sender simply discards any corrupted ACK frames or ignores out-of-order frames. The receiver can check the sequence number of each incoming frame for possible duplicate frames. If a frame is duplicated, the receiver will discard it.

Piggybacking in flow control of DLL

In full-duplex transmission, there is birectional communication of frames between sender and receiver. Frames can be transmitted in both directions using separate channels (forward and reverse), both channels having the same capacity. When a data frame arrives, the receiver waits and does not return a control frame (acknowledgement) immediately. The receiver then waits for its network layer to input the next packet. An acknowledgment is then appended to that outgoing data frame. Therefore, the acknowledgment is propagated with the next data frame. This technique of temporarily delaying outgoing acknowledgments is called piggybacking. The

Sling Window Protocols (continuous flow control) in DLL

sling window is basically an imaginary box for the transmitter and receiver. This window holds sender and receiver frames and proves an upper limit on the number of frames that can be transmitted before an acknowledgment is received. The area that affects the sender is called the sending sling window, and the area that affects the receiver is called the receiving sling window. One of the important features of all sling window protocols is that each outgoing frame contains a sequence number from 0 to some maximum value. The maximum value is usually the same (2 increases to “n” – 1). where “n” is any number. Those frames that are allowed to be sent are within the send window. The receiver also maintains a receiver window. It corresponds to the set of frames that the receiver is allowed to accept. The sender and receiver windows can have different sizes. A positive or negative acknowledgment (ACK or NAK) should be used after each frame. This means that the sender sends the frame, waits for an acknowledgment and sends the next frame or retransmits the original frame (depending on a positive or negative ACK). When an acknowledgment arrives from the other end, the send window can move one or more slots to the right, and the receive window ensures that the correct data frame is subsequently received and the correct acknowledgment is sent. The size of the receive window is always 1. The receiving window is an abstract concept used to define an imaginary box of size 1 with a single variable Rn. When the correct frame arrives, the window then sles, and the sle is slot by slot.

Resending of Frame

When the timer expires, the sender resends any pending frames. Suppose the sender has sent frame 6, but the timer for frame 4 has timed out. This means that frame 4 is not acknowledged; the sender goes back and retransmits frames 4, 5, and 6. Hence, the protocol is called Go-Back-N ARQ. Both sender and receiver maintain their own sling windows. The sender sends as many frames as its own sling window size allows, and then waits for confirmation from the receiver. The receiver sends an acknowledgment with the number of the next frame the sender should send. Finally we have reached the end of this article. Stay tuned for more great content in this series. report this ad

What is the role of sliding window in flow control at data link layer?

Sliding Window

The sender sends multiple frames in a sequence, without waiting for acknowledgment. When its sending window is filled, it waits for acknowledgment. On receiving acknowledgment, it advances the window and transmits the next frames, according to the number of acknowledgments received.

What is flow control explain the function of stop and wait and sliding window protocol?

Stop-and-Wait Protocol. Sliding Window Protocol. 1. In Stop-and-Wait Protocol, sender sends one frame and wait for acknowledgment from receiver side. In sliding window protocol, sender sends more than one frame to the receiver side and re-transmits the frame(s) which is/are damaged or suspected.

Is stop and wait sliding window protocol?

No. In Stop and Wait protocol, sender sends single frame and waits for acknowledgment from the receiver. In Sliding window protocol, sender sends multiple frames at a time and retransmits the damamged frames. Stop and Wait protocol is less efficient.

What is stop and wait protocol in data link layer?

Stop – and – Wait protocol is data link layer protocol for transmission of frames over noiseless channels. It provides unidirectional data transmission with flow control facilities but without error control facilities. This protocol takes into account the fact that the receiver has a finite processing speed.

How sliding window protocol are used for flow control?

Sliding window protocol is a flow control protocol. It allows the sender to send multiple frames before needing the acknowledgements. Sender slides its window on receiving the acknowledgements for the sent frames. This allows the sender to send more frames.

What is sliding window protocol with example?

It is a data link layer protocol that helps a sliding window method. In this, if any frame is manipulated or lost, all subsequent frames have to be sent again. For example, in GO- Back –N, the N is the sender’s window size; if it is GO-Back-5, the sender will send frame 1 to 5 before receiving the knowledge of frame 1.

What is the advantage of sliding window flow control compared to stop and wait flow control?

1 – What is the advantage of sliding-window flow control compared to stop-and- wait flow control? The stop-and-wait approach requires acknowledgements after each frame. The sliding-window flow control technique can send multiple frames before waiting for an acknowledgement.

What is advantage of sliding window protocol?

The sliding window provides several benefits:

It controls the speed of transmission so that no fast sender can overwhelm the slower receiver;
It allows for orderly delivery, as we will show;
It allows for retransmission of lost frames, specific retransmission policy depends on the specific implementations.

How does stop and wait protocol work?

What is Stop and Wait protocol? Here stop and wait means, whatever the data that sender wants to send, he sends the data to the receiver. After sending the data, he stops and waits until he receives the acknowledgment from the receiver.

What is flow control protocol?

Definition. Flow control is a synchronization protocol for transmitting and receiving units of information. It determines the advance of information between a sender and a receiver, enabling and disabling the transmission of information.

Where is stop and wait protocol used?

It is used in Connection-oriented communication. It offers error and flows control. It can be used in data Link and transport Layers. Stop and Wait ARQ executes Sliding Window Protocol with Window Size 1.

How sliding window protocol can be used to increase the efficiency of stop and wait protocol?

Efficiency Improvement-

The efficiency of stop and wait ARQ can be improved by increasing the window size.
This allows the sender to keep more than one unacknowledged frame in its window.
Thus, sender can send frames in the waiting time too.

What is stop-and-wait flow control with example?

Stop-and-wait flow control is the simplest form of flow control. In this method the message is broken into multiple frames, and the receiver indicates its readiness to receive a frame of data. The sender waits for a receipt acknowledgement (ACK) after every frame for a specified time (called a time out).

What are the protocols in data link layer?

The Data Link Layer protocols are Ethernet, token ring, FDDI and PPP. An important characteristic of a Data Link Layer is that datagram can be handled by different link layer protocols on different links in a path.

What is the difference between stop-and-wait and stop-and-wait ARQ *?

Working of Stop & Wait ARQ is almost like Stop & Wait protocol, the only difference is that it includes some additional components, which are: Time out timer. Sequence numbers for data packets. Sequence numbers for feedbacks.

See some more details on the topic Sliding Window and Stop – Wait protocol for Flow Control in data link layer here:

Data-link Control & Protocols – Tutorialspoint

This flow control mechanism forces the sender after transmitting a data frame to stop and wait until the acknowledgement of the data-frame sent is received.

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Stop and Wait Protocol – Javatpoint

The stop and wait protocol is a flow control protocol where flow control is one of the services of the data link layer. It is a data-link layer protocol …

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