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Before you go through this article, make sure that you have gone through the previous article on Stop and Wait Protocol.

stop and wait protocol

In this article, we will discuss practice problems based on stop and wait protocol. If the bandwidth of the line is 1. A channel has a bit rate of 4 Kbps and one way propagation delay of 20 msec.

The channel uses stop and wait protocol. The transmission time of the acknowledgement frame is negligible. What is the throughput achievable in stop and wait protocol by a maximum packet size of bytes and network span of 10 km. At what data rate does the round trip delay equals the transmission delay for a 1 KB packet? Host X sends a file of 50, bytes as one large message to host Y continuously.

Let the transmission and propagation delays be p milliseconds and q milliseconds respectively. Assume that there are no transmission errors.

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A sender uses the stop and wait ARQ protocol for reliable transmission of frames. Size of an acknowledgement is bytes and the transmission rate at the receiver is 8 Kbps.

stop and wait protocol

The one way propagation delay is msec. Using stop and wait protocol, sender wants to transmit 10 data packets to the receiver. Out of these 10 data packets, every 4th data packet is lost. How many packets sender will have to send in total? Get more notes and other study material of Computer Networks. Computer Networks. Stop and Wait Protocol Practice Problems. Practice Problems based on Stop and Wait Protocol.

Stop-and-wait ARQ

Stop and Wait Protocol is a flow control protocol where sender sends one data packet and then stops and waits for its acknowledgement. Akshay Singhal. Publisher Name. Liked this article? Share it with your friends and classmates now.Stop-and-wait protocol and Sliding window protocol are the methods evolved for handling the flow control of the network data transfers. These methods mainly differentiated by the techniques they follow such as stop-and-wait uses the concept of the acknowledging each data unit before sending another data unit.

Conversely, sliding window protocol allows the transition of the several data units before sending an acknowledgement. Among the two protocols, the sliding window protocol is more efficient than the stop-and-wait protocol. In a communication, if the speed of transmitting data at the sender end is very much higher than the speed of reception of data at the receiver end, how the network is going to deal with these kinds of cases?

stop and wait protocol

It requires the working speed of sender and receiver should be unvarying. The stop-and-wait protocol has emerged as a solution to this problem. In this protocol, the sender sends a frame then waits for the acknowledgement.

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When the receiver sends an acknowledgement to the sender, it proceeds further and sends another frame. The transmission mode of the protocol is half duplex, as the sender transmits data to the receiver at a time and receiver sends the acknowledgement when data is received.

The example of the stop-and-wait protocol is the RPC Remote Procedure Call because it works in the similar pattern where the subroutine calls are implemented from the program in one device to the library routines on another device.

As most programs are single-threaded, which make the sender wait for the reply before proceeding and sending other requests. Like stop-and-wait protocol, sliding window protocol is also a method to implement the flow control mechanism. It has eliminated the drawback of the stop-and-wait protocol where the restricted amount of data can be transmitted in one direction at a time. The performance of the sliding window protocol has improved by sending multiple frames bidirectionally at the same time i.

In this scheme, the sender sends sequentially numbered frames to the recipient in order to keep track of the frames, if the header size is n bit the sequence can range from 0 to 2 n The window here signifies a buffer utilised to store the data till the receiver does not read it, after reading the content the buffer is emptied.

It uses two types of windows, sending window and receiving window which can range up to 2 n The TCP protocol works as the sliding window protocol and uses a buffer placed in the kernel of the operating system.

Both of the protocols, stop-and-wait and sliding window protocol provides the mechanism for flow control.Flow control in computer networks is defined as the process of managing the rate of data transmission between two systems nodesthis mechanism ensures that the rate of data transmitted by the sender is within the receiving capacity of the receiver node.

After receiving the feedback, if the feedback is positive then the sender node sends the next data packet otherwise resends the damaged packet.

But this protocol has some issues, one such issue is the probability of occurrence of deadlockwhich is very high due to loss in a data packet or loss in feedback which can lead to infinite waiting, where the sender will keep on sending the data packet if the feedback is lost.

Networking: Unit 3 - The Transport Layer - Lesson 7, Stop and Wait

Note: If any sliding window protocol must work properly then, the available sequence numbers must be greater than or equal to the sum of sender window size and receiver window size.

For solving this problem, we use time out timer, after transmitting the data packet to the receiver through the communication channel, the sender starts the time out timer.

Now if the data packet's feedback is received by the sender before the timer expires, then the sender stops the timer and transmits the next data packet. And if the time out timer expires and the feedback is not received by the sender then, the sender retransmits the data packet. This prevents the occurrence of deadlock in the network. Assume that the feedback given by the receiver is lost, then the sender resends the same data packet after its timer expires. This prevents the occurrence of deadlock.

So, the sender sends a data packet and waits for the feedback, and it gets the feedback it sends another data packet. Made with by Abhishek Ahlawat. Ruby Servlet JSP. Operating System. Computer Architecture. Jenkins Maven. Apache Cordova Drools. We are Hiring! Sign in. Then, waits for the feedback of the transmitted packet.

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As soon as the receiver node receives a data packet it starts processing it. Then, the receiver node sends the feedback to the sender node about the received data packet.

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An illustration of the process is shown in the image below. Improving Efficiency In order to improve efficiency, we can increase the window size on both ends. Subscribe and receive amazing posts directly in your inbox. What is Studytonight? All rights reserved.While sending the data from the sender to the receiver the flow of data needs to be controlled. Suppose a situation where the sender is sending the data at a rate higher than the receiver is able to receive and process it, then the data will get lost.

Stop and Wait ARQ

The Flow-control methods will help in ensuring that the data doesn't get lost. The flow control method will keep a check that the senders send the data only at a rate that the receiver is able to receive and process. There are mainly two ways in which this can be achieved i. In this blog, we are going to learn about the Stop-and-wait protocol. It is the simplest flow control method. In this, the sender will send one frame at a time to the receiver.

The sender will stop and wait for the acknowledgment from the receiver. This time i. When the sender gets the acknowledgment ACKthen it will send the next data packet to the receiver and wait for the acknowledgment again and this process will continue as long as the sender has the data to send.

This can be understood by the diagram below:. The above diagram explains the normal operation in a stop-and-wait protocol. Now, we will see some situations where the data or acknowledgment is lost and how the stop-and-wait protocol responds to it. Suppose if any frame sent is not received by the receiver and is lost. So the receiver will not send any acknowledgment as it has not received any frame.

Also, the sender will not send the next frame as it will wait for the acknowledgment for the previous frame which it had sent. So a deadlock situation arises here. To avoid any such situation there is a time-out timer. The sender waits for this fixed amount of time for the acknowledgment and if the acknowledgment is not received then it will send the frame again.

Consider a situation where the receiver has received the data and sent the acknowledgment but the ACK is lost. So, again the sender might wait till infinite time if there is no system of time-out timer. So, in this case also, the time-out timer will be used and the sender will wait for a fixed amount of time for the acknowledgment and then send the frame again if the acknowledgement is not received.

There are two types of delays while sending these frames:. The propagation delay for sending the data frame and the acknowledgment frame is the same as distance and speed will remain the same for both frames. Hence, the total time required to send a frame is:. The sender is doing work only for Td time useful time and for the rest 2Tp time the sender is waiting for the acknowledgment. The number of bits that a receiver can accept in total time duration i.

It is also called effective bandwidth or bandwidth utilization. In Stop and Wait, in the total duration, the receiver can accept only one frame. One frame is of data size D i. D bits in one frame. This is how the flow of data is controlled using the stop-and-wait protocol.

Hope you learned something new today. Do share this blog with your friends to spread the knowledge.In the last tutorial, we have studied about the various delays in computer networks. In this tutorial, we will study about the first method of flow control i. Stop and wait ARQ. Sometimes, the speeds of the sender and the receiver might be different and thus to send data without any hindrance or data loss we need Flow control methods.

As the above image depicts, — Packets are sent one by one. After one packet is processed the receiver would send acknowledgement and request for next packet. If there is a match, data is accepted or else it is discarded. Assume using stop and wait protocol, we wish to send 10 packets from source to destination and every 4th packet is lost.

How many packets needs to be sent? Solution — Order in which packets are sent — 1 2 3 4 4 5 6 7 7 8 9 10 Assume a channel having error probability.

Solution — Total no. That was all about Stop and wait ARQ.

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In next tutorial, we will study about Go back N and selective repeat flow control methods. If you need, you may visit Android Tutorial for beginners page. You can also check Kotlin Tutorial for beginners. Also, if you are interested in content writing, you can mail us at tutorialwing gmail. Support Us If you like Tutorialwing and would like to contribute, you can email an article on any educational topic at tutorialwing gmail.

We would love to publish your article. See your article on Tutorialwing and help others with your knowledge. Related Posts.Next frame is transmitted only when the first frame is acknowledged. So there is no chance of frame being lost. It makes the transmission process slow. In this method single frame travels from source to destination and single acknowledgment travels from destination to source.

As a result each frame sent and received uses the entire time needed to traverse the link. Moreover, if two devices are distance apart, a lot of time is wasted waiting for ACKs that leads to increase in total transmission time. Dinesh authors the hugely popular Computer Notes blog.

Where he writes how-to guides around Computer fundamentalcomputer software, Computer programming, and web apps. For any type of query or something that you think is missing, please feel free to Contact us.

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Computer Networking. Related Articles Communication Network. About Dinesh Thakur. Related Articles. What is transmission media? Types of transmission media. Data Communication - What is Data Communication? What is Data Transmission? Types of Data Transmission.

What is Congestion Control? IEEE Characteristics of Analog Signal. Microwave Transmission — What is a Microwave Transmission? What is Fiber Optics Optical Fiber?Rule 1 Send one data packet at a time. Rule 2 Send next packet only after receiving acknowledgement for previous.

Rule 1 Send acknowledgement after receiving and consuming of data packet. Rule 2 After consuming packet acknowledgement need to be sent Flow Control. Time Out:. Sequence Number Data. Delayed Acknowledgement: This is resolved by introducing sequence number for acknowledgement also.

The Stop and Wait ARQ solves main three problems, but may cause big performance issues as sender always waits for acknowledgement even if it has next packet ready to send. Consider a situation where you have a high bandwidth connection and propagation delay is also high you are connected to some server in some other country though a high speed connection. To solve this problem, we can send more than one packet at a time with a larger sequence numbers. We will be discussing these protocols in next articles.

So Stop and Wait ARQ may work fine where propagation delay is very less for example LAN connections, but performs badly for distant connections like satellite connection.

This Article is contributed by G. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above. Writing code in comment?

Flow Control - STOP & WAIT and STOP & WAIT ARQ Protocol

Please use ide. Characteristics Used in Connection-oriented communication. Receiver: Rule 1 Send acknowledgement after receiving and consuming of data packet. Load Comments.