Channel utilization of backward n-frame protocol
The N-frame Backoff (GGN) protocol allows the sender to send multiple data frames in succession to improve channel utilization. In the stop-and-wait protocol, the sender could only send one frame at a time, and the channel utilization rate was low. However, GGN adopted the sliding window method, and the sender maintained a set of sending windows, which could send multiple data frames at a time.
The calculation of channel utilization is related to many factors, such as data transmission rate, one-way transmission delay, data frame length, etc. Suppose the data transmission rate is R (bit per second), the one-way transmission delay is T (s), and the data frame length is L (bit). In an ideal situation, the sender can continue to send data frames without considering errors and retransmissions during transmission. At this time, the channel utilization can be approximately expressed as: =
Channel utilization calculation of backward n frame protocol
1. ** sender's angle ** - Let the time to send a frame be <T_f>, the transmission delay be <T_p>, and the size of the sending window be <W>. - In the stop-and-wait protocol (transmit window <<W = 1>>), the channel utilization rate <U>=<frac>{T_f}{T_f +2T_p}>. - For the backward frame protocol (GGN), the sender can send a continuous number of frames. The total time it takes for the sender to send the W frames is W, and the total time from the start of the transmission to the time it receives the first acknowledgment frame (assuming it is received correctly) is W. - Therefore, the channel utilization rate is <U>=<frac>{WTf>}{WTf +2Tp>}. 2. ** Receiving angle ** - The receiver used the cumulative confirmation method. - Assuming that the sender sent a number of frames, the receiver will discard all the frames after the number of frames. - The sender needs to re-transmit all the frames starting from the <k> th frame, which will affect the channel utilization. In the ideal case (error-free transmission), the channel utilization rate is calculated as before. In the case of errors, the channel utilization rate will be reduced due to retransmissions. The specific degree of reduction depends on the frequency and location of errors. 3. ** Overall consideration ** - The channel utilization is also related to the number of digits in the frame number, because the transmit window size, W, has a maximum limit, W'leqslant2 ^n- 1. When W is close to this maximum value, the channel utilization rate can be improved without error, but it also increases the risk of frame number confusion (like the example of the 2-bit number mentioned earlier). Once the error is retransmitted, the channel utilization rate will be greatly affected. "Choose" was equally exciting. Everyone was welcome to read it!
Backward n frame protocol and selective repeat protocol
Go-back- N (GGN): - In the stop-and-wait protocol, the sender can only send one frame at a time, and the channel utilization rate is low. However, the backward N-frame protocol uses a sliding window method, and the sender maintains a set of sending windows, and can send multiple data frames at a time. The receiver uses the method of cumulative confirmation, and the sender moves the sending window forward after receiving the confirmation. When there was a problem (such as frame loss or long delay), the sender used the method of retreating N frames to re-transmit. The timer here was used to recover data frames or confirm the loss of frames, similar to the timer in the pause protocol. Choosing the Repeat protocol: - Different from the N-frame backward protocol, when the receiver receives an out-of-order frame, it will not discard all subsequent frames like the N-frame backward protocol. Instead, it will buffer the correctly received out-of-order frame. When the sender found that a frame was lost, it only retransmitted the lost frame, instead of retransmitting the subsequent N frames from the lost frame like the backward N frames protocol. This could avoid unnecessary data retransmissions and improve transmission efficiency, especially in a poor network environment with a high packet loss rate. Both of these two types of protocol were designed to deal with the loss of frames and the disorder of order during data transmission to improve the reliability and efficiency of data transmission. However, the specific ways in which they dealt with the problem were different. "Choose" was equally exciting. Everyone was welcome to read it!
How to calculate the channel utilization rate of the selected replay protocol?
Let the transmission delay + the round-trip delay + the reception delay be the transmission period of one frame, and the continuous period is the ARQ. The channel utilization rate of (including the selection of the re-transmission protocol) is more than that of the stop-and-wait protocol by (n)(window size). The channel utilization rate of the stop-and-wait protocol is (<<<frac><br>><<br>></>>)(where <<br> is the transmission delay,<<<Ta>> is the reception delay, and <<<br> is the round-trip delay). Therefore, the calculation formula for the channel utilization rate of the chosen replay protocol <<br> is <<frac>{n <times><>></>><). At the same time, the number of bits in the frame sequence number is set to <<k>>, and the transmission window of the <<PR>> protocol is usually <<<leq2 ^{k}-1>>. In the case where both <<T>> and <<T>> are determined, the larger the <<N>>, the greater the channel utilization. "Choose" was equally exciting. Everyone was welcome to read it!
Fallback N-frame protocol
The Fallback N-frame protocol (GGN) was a continuous ARQ protocol. It was based on the pipeline transmission and used the transmission window to limit the number of packets that the sender could continuously send. Both the sender and the receiver use a certain number of bits to number the packets and use them repeatedly. The sender has a sending window, and the data packets whose sequence number falls within this window can be sent continuously without waiting for a reply. The size of the sending window is recorded as Wt, and the size of the receiving window is recorded as Wr. For the fallback N-frame protocol, Wr is usually taken as 1. Packets with sequence numbers falling within the receiving window can be received. Every time a packet is received, the receiving window will slide back and send a confirmation packet (using the cumulative confirmation method). The advantage of this kind of cumulative acknowledgment is that even if the acknowledgment packet is lost, the sender may not need to re-transmit, thereby reducing the overhead of the receiver and the occupation of network resources. When there is an error or interference, the receiver will discard the packet and the subsequent packets, and send an acknowledgment of the most recently received packet. Once the time-out timer is expired, these packets will all be retransmitted (that is, the N frames that have been sent out will be retransmitted from the error). However, if Wt exceeds the upper limit of its value (if the frame sequence number is numbered with n bits, then Wt <2-1), it may cause serious errors. For example, the receiver may not be able to distinguish between old and new packets, resulting in repeated packets. Moreover, the channel utilization rate may not be higher than that of the stop-and-wait protocol. "Choose" was equally exciting. Everyone was welcome to read it!
Fallback n frame protocol sending window size
The size of the sending window of the fallback N-frame protocol is greater than 1, and multiple data packets can be sent consecutively. " Choose " was equally exciting. Everyone was welcome to read it!
Food scraps utilization
The following are some ways to use food scraps: - ** Fruits ** - ** Banana peel **: It can be chopped and cooked first, then packaged in a frozen package. When you want to eat it, you can directly take it out and heat it up to fry it. However, banana peels contained more impurities, so the flavor would be slightly astringent. - ** Orange peel **: It is rich in oil and has a strong fragrance after being heated. It can be made into snacks or drinks. For example, the dry orange peel was cut open, the flesh was scraped out, and then processed according to the method of apple preserved fruit processing. The dry orange peel could also be heated with tea to extract the fragrance and drink it. - ** Orange peel **: Also known as orange peel, it can be soaked in water to drink. People who have motion sickness can smell fresh orange peel to relieve motion sickness. It can also be used to make orange peel sauce, shredded orange peel, orange peel soup, and other delicacies. - ** Meat and internal organs ** - ** Beef jerky scraps (beef jerky feathers)**: Beef jerky scraps that are more expensive in supermarkets. After heating them in an air frying pan, they are very fragrant. Some of them have tendons and can be added to noodles. - ** Tripe shreds **: 30 yuan can buy 5 catties. It has already been cleaned. A simple rinse can make an entire pot. - ** Vegetables ** - Celery leaf: It has a special fragrance and is rich in calcium, iron, potassium, and vitamins A and C. It can be used to make celery leaf mixed with fungus, celery leaf dumplings, celery leaf bread, etc. - ** Radish Tassels **: The nutritional value is higher than the radish root in many aspects. Eating it often is good for the eyes. It has a high level of diet fiber and can be used to make dishes. - Watermelon rind: Also known as Watermelon Cuiyi. It can be used to make watermelon rind salad, watermelon rind egg soup, watermelon rind fried meat, etc. It can also be used to make soup, such as watermelon rind, poria cocos and licorice soup. - ** Grains ** - ** Remaining Dough **: Can be used to make simple pastries such as dough pieces and dough lumps. Roll the dough into thin slices, cut it into small pieces, and cook it. - [The remaining rice grains can be used to make porridge or ground into vermicelli.] After washing the rice grains, he added an appropriate amount of water and boiled them into porridge or ground them into powder to make rice noodles. - ** Others ** - [Fish Scale: Rich in nutrients. Can be used to make fried fish scales, fish scale jelly, and other delicacies.] When using kitchen scraps, pay attention to hygiene and wash them to ensure the safety of the ingredients. For perishable ingredients, such as vegetables and meat, they should be properly preserved to prevent deterioration. They can be placed in sealed bags and stored in the refrigerator. At the same time, they should give full play to creativity to turn scraps into treasures. The novel "Ledge" is equally exciting. Everyone is welcome to click and read it!
Waste utilization of cloth scraps
There were many ways to make use of cloth scraps. It could be recycled and made into cotton, which could increase the profits of the company and conform to the concept of circular economy. The waste cloth could also be made into pellet fuel, which had a high heat value and cost about 300 - 400 yuan. It could be used in cement plants, biological power plants, and large enterprises. In daily life, cloth scraps were also widely used. It could be used to make all kinds of household items, such as pillows, all kinds of cushions, quilts, storage baskets, storage bags, key bags, storage baskets, cloth dolls, etc. He could also make decorations, such as making YOYO flowers to sew table mats, embellishing bags, or combining them with old cardboard to make photo frames. It could also be used to make handmade cloth baskets or baby undergarments. In addition, he could also combine the pieces of cloth to make some creative items, such as using pieces of cloth, single tape lining, cotton, base cloth, lining cloth, sewing thread, zipper and other materials to make unique items. The novel "Ledge" is equally exciting. Everyone is welcome to click and read it!
Waste utilization manual work
The following are some examples of manual waste recycling: ** 1. Kitchen Items ** 1. ** Self-made chopping board and knife rack ** - [Material: A bottle of dishwashing liquid.] - Steps: Cut off the top of the dishwashing liquid bottle along the line, leaving only a part. The two sides were lined vertically and cut in a symmetrical manner. It could be used to place kitchen chopping boards and kitchen knives for convenient ventilation and to prevent the chopping board from moldy and growing hair. 2. ** Self-made seasoning bottle ** - [Material: Bottle cap] - Steps: Bake the bottle cap with fire, use a toothpick to top it, and then cut off the top. You can make a seasoning bottle that can control the amount of seasoning. 3. ** Washing pad draining rack ** - [Material: A bottle of dishwashing liquid.] - Steps: Cut the bottle according to a specific line, pierce a hole in the circle, and make a drainage hole at the bottom side by side. Hang it with a rope and use it to drain the scouring pad. ** 2. bathroom supplies ** 1. ** Water-proof toilet paper cover ** - [Material: Empty oil barrel] - Steps: Cut open the empty oil barrel, drill holes on both sides, cover it on the roll of paper, and put on a chopstick. Hang it in the bathroom to prevent the toilet paper from getting wet. 2. ** Self-made trash can ** - [Material: Oil control bottle] - Steps: Cut the oil control bottle in a specific way and wrap the edge to make a convenient trash can. ** 3. Other daily necessities ** 1. ** The divine tool for taking cups ** - [Materials: Empty bottle, disposable cup.] - Steps: Put the disposable cup on the head of the bottle, cut off the excess part of the bottle along the cup, cut it into a tassel shape, and then cut the bottom of the cup until it was not cut off. Make a hole on the side, find a place to hang it, and put the cup in to make the cup artifact. 2. ** Automatic watering artifact ** - [Materials: Bottle of water, cotton swabs, chopsticks.] - Steps: Make a small hole in the bottle cap, put the cotton swab in, fix the chopsticks on the bottle, wrap them with tape, and then insert them into the flower pot. 3. ** Watering pot ** - [Material: Empty bottle of used laundry soap.] - Steps: Burn some small holes on the bottle cap and one above the handle. It can be used as a watering can and can also control the flow of water. ** 4. Decorations and Originality ** 1. ** plastic flowerpot (like bunny plastic flowerpot)** - [Materials: Two plastic beverage bottles, animal head template, paint, scissors.] - Steps: Cut the plastic bottle into 10cm high and leave it at the bottom. He stuck the animal template on the plastic bottle and cut out the shape. After cutting it, he painted a layer of paint on the plastic bottle, then painted a layer of bright-colored paint on the animal's body, head, and facial features. Finally, he placed a small potted plant or directly filled it with soil and small plants. 2. ** plastic bottle bird feed ** - Materials: plastic bottle, paint, scissors, hot melt glue, paintbrush, rope, and other auxiliary tools. - Steps: Coat it with brown paint and stick a layer of tree bark to make it more realistic. 3. ** plastic bottle owl ** - Materials: plastic bottle, paint, pen, scissors. - Steps: First, roughly measure the bottle and cut it to a suitable length. 4. ** A plastic pen holder (can be used for storage and can be used for mischief, such as putting a small light bulb to scare a friend at night, white plastic bottle is required)** - [Material: plastic bottle] - [Steps: Directly use plastic bottles to make it.] 5. ** Storage rack for plastic bottles (made from discarded medicine bottles)** - [Materials: A piece of wood, scissors, nails, sandpaper, hammer, hand-drawn template, and several discarded cylindrical plastic bottles.] - [Steps: Follow certain steps to combine these materials.] 6. ** plastic bottle pine tree ** - Materials: 1.5L and 2L plastic bottles, A4 paper. - Steps: Cut the flat part in the middle of the 2L bottle into a 1cm wide strip. He used A4 paper to roll the trunk of a big tree and stuck it on the base of the big tree made of the plastic bottle. Then, he stuck the cut plastic strips on the trunk of the big tree with transparent tape. Pay attention to the length of the plastic strips from the bottom to the top, making layers. 7. ** A plastic bottle doll or doll ** - [Material: A plastic bottle for drinking water.] - Steps: According to the different shapes of the bottles, use creativity to decorate the bottles. 8. ** Small fan (suitable for kindergarten craftsmanship or parent-child craftsmanship)** - [Material: A finished beverage bottle.] - [Steps: Make a small fan according to a specific method.] While watching the Olympics, you can also read the wonderful novels related to the Olympics!
Continuous arq protocol and sliding window protocol
In the continuous ARQ protocol, the sender maintained a sending window of a certain size, and the packets within the window could be sent continuously without waiting for the other party's acknowledgment. The sender would slide the sending window forward by one packet every time it received an acknowledgment. The receiver usually uses the method of accumulating acknowledgement, that is, after receiving several packets, it sends an acknowledgement to the last packet that arrives in order, indicating that all the packets up to this packet have been received correctly. However, this method has shortcomings. For example, when the middle packet is lost, the sender cannot know the situation of the subsequent packets, and may need to re-transmit more packets. The sliding window protocol involves a sending window and a receiving window. The transmit window is the range of sequence numbers of the frames that have been sent but have not been acknowledged, and the receive window is the range of sequence numbers of the frames that are expected to be received. When the default window size is 1, you can operate according to the specific sending process. The sliding window protocol could improve the channel utilization and was a reliable transmission mechanism for data communication. The continuous ARQ protocol can be seen as a specific application form of the sliding window protocol under certain conditions (such as the cumulative acknowledgment method). They are all protocol mechanisms that exist to achieve effective and reliable data transmission in the network. "Choose" was equally exciting. Everyone was welcome to read it!