Go Back n protocol
The Go-Back- N protocol, also known as the sliding window protocol, was an automatic repeat request (ARQ) protocol. From the sender: - First, a transmission window of length N would be initialised. The sender can continuously send packets within the window and set a timer for the first packet in the window. - After sending the data packet, wait for confirmation from the receiver. If the acknowledgment is received before the timer is expired and there are still sent but unacknowledged packets in the window, the timer will be restarted; if all the sent packets in the window are acknowledged, the timer will be stopped. - If the sender does not receive an acknowledgment from the receiver before the timer expired, the sender will resend all the unacknowledged packets sent in the current window and restart the timer. At the receiving side, the method of cumulative confirmation was used. For example, the sender sends a packet of 43210, and the receiver receives a packet of 43210. The cumulative acknowledgment ack = 4 (it is the current acknowledgment packet number, not the next request packet number). When an error occurs, for example, the sender sends a packet of 543210, and the receiver receives 54310 (packet No. 2 is lost). The receiver's receiving window is stuck at packet No. 2, waiting for packet No. 2 to be confirmed. When packet No. 345 is received, the receiver will send three acknowledgement packets of ack = 1 to the sender (because three packets of 345 are received after packet No. 2, a packet of ack = 1 will be sent for every discarded packet). The GGN protocol used the sending window to limit the number of data packets that the sender could send consecutively, thus achieving reliable data transmission on the basis of pipeline transmission. "Choose" was equally exciting. Everyone was welcome to read it!
Go back, go back, go back, come back
The phrase "Go back, go back, go back, come back" was related to Tao Yuanming's Ci of Going Back and Coming. "Return to Xi Ci" expressed the author Tao Yuanming's yearning for rural life and his disgust for officialdom. In the article, there was a sentence: "Return to Xi, will the countryside not return?" Such famous sentences conveyed the feelings of returning to one's heart and leaving the secular world. In addition, the song was also used in modern songwriting. Different songs had different meanings, but most of them were related to emotions such as returning and searching for the heart. The novel " The Clouds Come and Go in the Sunset " is equally exciting. Everyone is welcome to click and read it!
Go back, come back
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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!
The difference between AH protocol and EP protocol
The difference between the gmn protocol and the sl protocol
Both GGN (Fallback N-frame protocol) and SSR (Random Repeat protocol) were sliding window protocol under the reliable data transmission protocol in computer networks. There were the following differences between the two: 1. ** Receiving window size ** - ** GGN protocol **: Receiving window <br>(W = 1 <br>), which means that the receiver can only receive the data packets that arrive correctly in order. If an error occurs in a data packet, it will cause the subsequent packets to be discarded because they cannot be received in order by the receiver, even if these packets are not error-free and out of order. - ** PR protocol **: If the receiving window size is greater than 1, the receiver can receive packets out of order. 2. ** Confirm Method ** - ** GGN protocol **: uses cumulative acknowledgment. The receiver acknowledges the last frame of a group of frames that arrive in order, indicating that all the frames before this frame have been received. For example, if the sender sends four frames 1, 2, 3, and 4, and the receiver acknowledges frame 4, it means that the four frames 1, 2, 3, and 4 have been received. The previous frames 1, 2, and 3 are no longer separately acknowledged. - ** PR protocol **: Each packet has a separate confirmation mechanism. The receiver can confirm each correctly received packet separately, and the sender can selectively re-transmit the incorrectly received packet according to the confirmation information of the receiver. 3. ** Retransmission mechanism ** - ** GGN protocol **: When the sender receives an acknowledgment for a frame, the sending window will be moved forward. If there is a packet loss or a long delay (such as a timer exceeding), the sender needs to resend all the packets that have been sent but have not been acknowledged. For example, if the sender sends six frames, frame 1, 2, 3, 4, 5, and 6, the receiver will confirm frame 3, and the sender will think that frame 1, 2, and 3 have been sent correctly. If there is a problem later, frame 4, 5, and 6 will need to be retransmitted. - ** PR protocol **: The sender only re-sends the packet that the receiver did not receive correctly, instead of re-transmitting all the sent frames after the acknowledgment frame like the GGN protocol. 4. ** Resource utilization and wastage ** - ** GGN protocol **: Due to the method of accumulating acknowledgement and returning N frames of retransmissions, the error of one packet may lead to the retransmissions of multiple packets, even if these packets themselves are error-free. This causes a waste of resources to a certain extent, especially when the window is large and the bit error rate is high. A large number of unnecessary packets may be frequently retransmitted. - ** SP protocol **: Compared to the GGN protocol, it is more resource-saving because it only reforwards the packets that the receiver did not receive correctly, avoiding unnecessary packet retransmissions and thus improving the channel utilization. However, there were some problems with the SSR protocol. For example, the receiver and sender windows were not synchronized, which could cause errors. "Choose" was equally exciting. Everyone was welcome to read it!
ARP protocol
The Address Resolution Protocol was a network layer protocol. It was between the data link layer and the network layer. It played a vital role in network communication, just like the address translator in the network. Its main function was to convert the IP address of the network layer to the data link layer's IP address. This was because in network communication, although the IP address was used to identify the host at the network layer, it was forwarded through the IP address at the data link layer (such as the ether network). The host or the layer 3 network device would maintain an ARP-table to store the IP address and the MAC-address map. The ARP-table entries included dynamic and static ARP-table entries. The working process was as follows: When host A needed to communicate with host B, it first determined the forwarded IP address according to the route table, and then checked the local ARP-buffer. If there was no matching address, it would broadcast an ARP-request frame in the network. All hosts in the same broadcast domain will receive this request. For example, after receiving the request, host C will find that the destination address is not its own, and then it will buffer the address of host A into its own ARP-table, and then discard the packet. After receiving the request, host B will find that the destination address is its own, and then it will buffer the address of host A and give a response. Then it will package its own address in the response ARP-packet and send it to host A. After receiving the response, host A will update its own ARP-buffer. There were two ways to obtain the ARPs: static and dynamic. The static acquisition was equivalent to manually configuration of the address map in the ARP-table. If the physical address changed, it would need to be manually changed, which was more troublesome. The dynamic acquisition was to obtain and update the address map by the host through the protocol, which was relatively convenient. In addition, there was also a free ARP-type message that was used to detect whether there was an IP address conflict. It would send a broadcast message with the same source and destination IP. Under normal circumstances, it was not expected to receive a response. If a response was received, it meant that there was an address conflict. In the Windows system, there were related ARP-commands. For example, ARP-a could check the ARP-buffer table, and ARP-d could delete the ARP-buffer table. However, due to network communication requirements, the buffer table might be regenerated immediately. In November 1982, the Internet Engineering Task Force (IetF) published the Internet Packet Packet Interface Problem (ARPG) 826. It was an indispensable protocol for the Internet Packet Interface Version 4, which was the most widely used version of the Internet protocol.(The Internet Packet Interface Version 6 was still in the early stages of deployment.) The role of the ARP-protocol in the car's ether network was the same as that of the traditional ether network. "Choose" was equally exciting. Everyone was welcome to read it!
protocol translation
The price quoted for contractual translation was usually affected by many factors: 1. ** Language pair **: Common ones such as Chinese-English translation may cost 200 - 400 yuan per 1,000 words; translation between minor languages and Chinese may cost 300 - 500 yuan per 1,000 words. 2. ** The complexity of the agreement **: For general agreements, the terms are relatively common and simple, and the fee is relatively low, about 200 - 300 yuan/1,000 words; for agreements involving complicated legal terms, professional terms, and strict format requirements, the fee may be 350 - 500 yuan/1,000 words. 3. ** Delivery Time **: During the normal delivery period, the above standard charges will be applied. If the customer requests urgent delivery, an additional fee may be added. 4. ** Translator's Quality Requirement **: Standard quality, able to accurately convey the content of the agreement, moderate fee; High quality, accurate language, compliance with legal documents, high fee. In general, the price of the contract translation was about 200 - 500 yuan per thousand words. The specific price still needed to be confirmed in detail. In addition, the word "protocol" has different meanings in different scenarios. In the Internet industry, it has the meaning of "protocol"(for example, the full name of the IP address is Internet Protocol Address). In the political context, it is inclined to reach a political consensus, rule, or speech technique (such as political protocol). In the diplomatic context, it means a set of rules or etiquette (such as diplomatic protocol). When translating the protocol, you need to accurately understand the meaning of these words in different context. "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!
Go back to 1980 and be a millionaire
There were many ways to become rich in the 1980s. First of all, they could take advantage of the market demand for some emerging things at that time. For example, the market demand for gifts and accessories was strong. They could cooperate with factories to mass produce gold and silver jewelry, watches, leather goods, and other gifts and accessories, and then use markets, shops, department stores, and other channels to sell them. Candies and pastries were loved by children, so they could engage in related production and sales. In terms of electrical and electronic products, many households at that time did not have household appliances such as televisions and washing machines. This was also a market that could be developed. With the improvement of people's living standards, the pursuit of fashion trends also brought business opportunities. There was also a market for photo processing shops, as home cameras were becoming more common. They could also engage in the business of selling goods, such as buying clothes and small electronic products in the south, and then setting up stalls in small cities to sell them. Or they could seize some special opportunities, such as discovering business opportunities at trade fair, or they could discover business opportunities while studying in Japan. They could also try to set up small township enterprises, acquire state-owned enterprises related to urban industries, or engage in bulk commodity trade and participate in the stock market in the early 1990s. In addition, some simple ways of starting a business, such as participating in product packaging to obtain subsidies when he was young, selling doll paper, and doing business with Nintendo's red and white machines, were also ways to make money at that time. Of course, these methods needed to be based on the actual situation at the time, with a keen market insight, courage to try and work hard, and many other factors to successfully become a rich man. The novel " Reborn in a Small Mountain Village in the Eighties " is equally exciting. Everyone is welcome to click and read it!
Go back to the West
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