Fallback n frame protocol value range

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!

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!

In the fallback N-frame protocol, the transmission window Max <= the size of the serial number space- 1. For example, if the serial number is identified by a 3-digit system (0 - 7), and the serial number space is 8, then the transmission window must be less than or equal to 7. This limitation was mainly to avoid confusion during the process of sending and receiving confirmation, causing the sender to be unable to accurately determine which group of data frames the confirmation frame was for. "Choose" was equally exciting. Everyone was welcome to read it!

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!

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: <U>=<frac{L}>{(2T +<frac{L}{R})R}>. In the GGN protocol, the larger the transmission window, the more data frames allowed to be transmitted, and the higher the channel utilization rate. However, the transmission window could not be infinitely large. When using n bits to code, the maximum transmission window is <<2> n>-<1>. However, if there was an error and the transmission needed to be repeated, the GGN protocol's transmission mechanism would affect the channel utilization. Since GGN uses a cumulative acknowledgment method, the sender will move the sending window forward after receiving the acknowledgment. If the sender does not receive the acknowledgment or receives a negative acknowledgment (NAC), it needs to retreat N frames and resend all the sent frames after the acknowledgment frame. When an error occurs, the frame that has been transmitted correctly will also be retransmitted, thus reducing the channel utilization to a certain extent. "Choose" was equally exciting. Everyone was welcome to read it!

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!

Generally speaking, the newborn's transcutaneous-Bilirubin value (TCG) was considered normal for full-term infants <12.9 and preterm infants <15. From the perspective of plasma Bilirubin value, it was normal for full-term infants to be lower than 221 micromole/L (12.9) and preterm infants to be lower than 255 micromole/L (15). However, different laboratories and testing methods may cause differences in the normal values of TCG in newborns. The normal values may also be within the range of 0 - 1 milligram per liter or micromole units. In addition, the newborn's serum level was affected by many factors, such as the physical condition at birth, breast-feeding and diet. In the diagnosis and treatment, the newborn's age, age, weight, and whether there are any high-risk factors should be considered. It could not be judged based on the results of a single examination. "The Island of Life" is also a wonderful novel. Everyone is welcome to read it!

If n bits are used to number the frames, in order to prevent the new receive window from overlapping with the old receive window after the receiver moves the window forward, the maximum size of the transmit window should not exceed half of the range of the sequence number, that is, WT< 2n-1. When the transmit window is the maximum, it is the same as the receive window. In most cases, the transmit window is equal to the receive window and is equal to 2n-1, because the maximum efficiency can be achieved in this case. Here, n represents the number of digits of the frame number, and the setting of the frame number range is related to this n, and must satisfy the above restrictions on avoiding window overlap. " Choose " was equally exciting. Everyone was welcome to read it!

Among Canon's full-frame single-lens reflex cameras, the Canon 5D3 was the recommended model for mid-range single-lens reflex cameras. It had 22.3 million pixel-sized full-frame and cost about 4500 yuan. It had a 61-point focus, digic5 +, and dual slots of TF +SD. The quality was good, and it was enough for personal amateur photography. The price-performance ratio was relatively high. The Canon 5D4 was also a good full-frame single-lens reflex camera. It had 30.4 million resolution and cost 14999 yuan. Not only did it have outstanding still photo quality, but it was also good at recording 4K videos. <a href="/?from=ask_words" style="color:red" target="_blank">Read more exciting novels for free</a>

The following are the normal ranges for all indicators of newborns: 1. ** Weight **: The normal range is 2500 - 4000 grams. A baby boy will be slightly heavier than a baby girl. The standard birth weight of a baby boy is 3.3 kilograms, and the standard birth weight of a baby girl is 3.2 kilograms. Generally speaking, the normal birth weight of a full-term newborn is 5 to 8 kilograms, and many newborns are about 3.5 kilograms. 2. [** height **: The normal range is 46.5 - 53cm. Male babies will be slightly taller than female babies.] 3. ** Head circumference **: The normal range is between 32 - 36cm, with an average of 33 - 35 cm, and the average is about 34CM at birth. 4. ** Chest circumference **: The normal range is between 30 - 32cm, with an average of 32.4 cm. Generally, it is 1 - 2 cm smaller than the head circumference. 5. ** Skin **: Generally, it begins to turn yellow after 2 - 3 days of birth. The peak period is 4 - 5 days after birth. It will gradually disappear after a week (physiological yellowness), but it is normal for some babies to have yellow skin after birth. 6. ** Breathing **: Mainly abdominal breathing. Breathing is shallow and fast, about 40 - 50 times per minute. 7. ** Heartbeat **: 90 - 100 beats per minute when asleep, 120 - 140 beats per minute when active, and even up to 160 - 180 beats per minute when crying. 8. ** Body temperature **: Normal body temperature is 36 - 37.5 ° C. 9. ** Limbs **: The tips of the fingers and toes may be slightly purple. 10. ** Dwelling and defecation **: Dark green feces will be discharged in the first 1 - 2 days after birth, and then it will turn golden yellow. Most newborns urinate 6 hours after birth, but the amount of urine and the frequency of urinating are small. After about a week, the amount of urine increases significantly. If there is no stool or urine for more than 24 hours, you need to see a doctor. 11. ** Vision **: When you are born, your vision is very low, but you have a sense of light. When strong light hits your eyes, your pupils will shrink. 12. ** Hearing **: After one week of birth, your hearing will gradually increase and there will be a physiological reaction. "The Island of Life" is also a wonderful novel. Everyone is welcome to read it!