[Windows] half-open connections

Introduction

At least three years ago, many download software, including thunder, provided the "Modify (crack) Operating System 'tcp half-open connection' quantity limit (" half-open connections "for short ") ", but some users do not understand it correctly.

What are "TCP semi-open connection" and "restrictions "?

The so-called "half-open TCP connection" is simply to say that a TCP connection request is initiated, but the connection is still in the established stage, and the two sides cannot communicate with each other.

The "limit on the number of TCP half-open connections" refers to the limit on the maximum number of TCP half-open connections that can exist at the same time by the connection initiator.

In Windows XP SP2, Microsoft introduced the limit on the number of half-open connections for the first time. The limit is 10. Restrictions include subsequent XP SP3, Windows 2003, Windows Vista, and vista sp1.

[However, Microsoft does not enable semi-open connection in Windows 7, Vista SP2, and Windows 2008]

Why modify the "TCP half-open connection" restriction?

I. Reduced the efficiency of connecting multiple resources

If we compare the above "connection phase" to a customer who is cooking in a canteen, it is much easier to understand.

1. the TCP half-open connection is limited to 10, which means that the canteen has 10 windows for simultaneous meals.

2. The system has a large number of requests with more than 10 TCP connections. This is equivalent to a large number of customers in this canteen, but they have to wait in line to wait for the first 10 customers to cook.

Obviously, the limit on the number of TCP half-open connections reduces the efficiency of establishing a TCP connection. Apply to the download tool. Because thunder may have a large number of candidate resources that need to be downloaded over TCP connection, the efficiency of connecting multiple resources is reduced.

2. When a program occupies 10 half-open connections in the full zone, other applications will be affected to initiate TCP connection requests.

Assume that all the connection requests are initiated by the same program (such as "Thunder"). In this case, the connection requests initiated by other programs (such as "browsers") must be queued due to the time consumption in the queue. When thunder is used for download, the website cannot be opened or the WebSite becomes slower.

Why does Microsoft limit the number of "half-open TCP connections?

According to Irvin, the reason for limiting the number of "half-open TCP connections" is that Microsoft wants to prevent the outbreak of a similar "Shock Wave virus. Infected machines initiate hundreds of thousands of connections and attack other computers.

However,Microsoft does not enable semi-open connection in Windows 7, Vista SP2, and Windows 2008.", But the restriction mechanism is retained. It may be because Microsoft decides that there is no need to limit the number of semi-open connections under normal circumstances. When the situation changes (such as a virus outbreak), Microsoft may re-enable the limit on the number of semi-open connections.

 

 

 

Get rid of the misunderstanding of the limit on XP half-open connections!

 

Recently I have seen some posts saying that "XP SP3 only allows 10 people to connect to your { Tagshow (Event) } "> Misleading comments such as computers deeply feel that" the more the layman teaches the layman, the more the layman "...... The correct statement is that XP SP3 only allows 10 TCP semi-open connections at the same time. 1. What is a TCP semi-open connection? The so-called half-open TCP connection simply sends a TCP connection request but has not yet received the response from the other party (in fact, it is more complicated), that is, the connection has not yet been fully established, the two parties cannot communicate with each other. 2. Does XP limit the number of TCP connections? XP SP3 does not limit the number of TCP connections. 3. limit on the number of semi-open connections ,{ Tagshow (Event) } "> Is there any effect on the download speed? Almost no impact. At best, the limit on the number of half-open connections only introduces a certain latency (from several milliseconds to several hundred milliseconds) during connection. Data interaction is transmitted over established TCP connections, and the transmission rate is independent of the number of semi-open connections. What's more, P2P protocols also have queues and request data. The latency introduced by these mechanisms is far greater than the latency caused by semi-open connection restrictions (for example, you have connected hundreds of peer ends, however, only dozens of data are transmitted, most of which are waiting or idle ). Therefore, the limit on the number of half-open connections has almost no effect on the upload and download speeds. 4. Number of TCP semi-open connections { Tagshow (Event) } "> How many settings are appropriate? It is recommended that the value not exceed 50. You do not need to set it too large. Because every half-open connection will { Tagshow (Event) } "> System (including vro, firewall ,{ Tagshow (Event) } "> Operating system, etc.) introduces additional overhead. Too many half-open connections can only cause system resources to be tight, unstable, or even crash, but cannot substantially increase the transmission rate. For example, in P2P { Tagshow (Event) } "> In the network, a hacker can guide a large number of clients to try to establish a connection with an attacker in a short time by spreading false resource information. If the number of half-open connections is too large, it will cause system crash (such as router infarction, firewall paralysis, or operating system crash ). There are many other DDoS attacks. Limit the number of TCP half-open connections to effectively prevent DDoS attacks. 5. How do I know the current transmission rate? Use the network tab of the task manager or the firewall to view the actual amount of data transmitted by the network adapter. Download { Tagshow (Event) } "> The value displayed by the software may be false. Finally, I hope you will not be superstitious about the rumors that the number of TCP semi-open connections will significantly increase the transmission rate. Actual transmission rate = number of simultaneous connections × percentage of valid connections (source) x average upload rate of the Peer upload channel x average transmission time; duration of Connection. , PM Taught Maybeonly2007-8-20, PM Well, the typical example is to upload Just like the previous QoS I used to move the so-called { Tagshow (Event) } "> Cracked ====== I am afraid the real reason is that, after rumors are spread, whose software does not have this { Tagshow (Event) } "> Functional people think that your software is not very good ~ Cough. I love rena2007-8-21, AM Well, I learned. Aurora_Boreas2007-8-21, 08:07 AM At present, it is mainly bandwidth { Tagshow (Event) } "> Problem. If you use lan... Zhongyb2007-8-21, AM Correct. I don't need to crack my computer again! 201710000000000002007-8-21, AM Learned In addition, the region name exceeds 200 pixels. Turbidity clear spring Pair Wong5202007-8-22, AM The pipe is thick! Lxshan2007-8-22, AM It seems that the original 500 is about to be changed to 50. Vanilla layer snow-8-23, AM Looks like and { Checkurl (this. href); Return false; } "Href =" http://bbs.verycd.com/topics/334324/ "target =" _ blank "> http://bbs.verycd.com/topics/334324/this inner conflicts Nagisa-Kaoru2007-8-23, AM I only know that, without unlocking concurrent connections, there will be very few seeds and sources for BT and donkey. Fuzzier2007-8-24, AM 11 floor: I posted a post to crack rumors. Floor 12: You are talking nonsense! The psychological effect is too serious. Kagami_sama2007-8-24, AM There is basically no difference between my k ADSL, which may be related to network conditions. Uralhan2007-8-24, AM Yes! I used neo in the intranet and found that the modification of the maximum number of semi-open connections was not affected. It is too common to spread rumors on the Internet. The key is that people who really know about the rumor may be dismissive, and few will be more authentic. Therefore, the rumor spread more widely. Gaver2007-8-24, AM I have heard that the number of connections will change back to the default value after the online upgrade. I haven't changed it for a long time. Happy weekend! YJeson2007-8-24, AM Very questionable !!! Most of the current books BT P2P include network TV ,{ Tagshow (Event) } "> The installation is accompanied by a reminder to lift the limit on the number of links. Are the developers of these software all cainiao and will do everything without verification !!! Very questionable !!! Zhang Hao I used to open 500. After reading this post, I changed it to 10. The speed of the result has not changed much. Therefore, I agree with LZ's remarks that the influence of half-open connections on speed is very small, the key lies in your bandwidth. I am an 8 m ADSL. Fuzzier2007-8-24, PM Reference (yjeson @, PM) Nowadays, most books, BT P2P, including network TVs, are installed with reminders to lift the limit on the number of links. Do the people who develop these software be cainiao and do everything without verification !!! Software development is not necessarily a cainiao. Instead, it gives users a cool to chew-the taste is true, but it is not that heavy. What level of people are most involved in software development in China? What is the mode? You can visit. And software development { Tagshow (Event) } "> Technology and network technology are two different things. Let's take a look at the foreign countries. There is no eMule mod or other download software that provides the function of modifying the XP semi-open connection restriction. The old ones are not so happy yet ^. RadishLi2007-8-24, PM I used to open 256. After reading this post, I changed it to 50. The result speed has not changed much. I am an 8 m ADSL high ID, and the speed of upstream and downstream traffic changes little. Pengfei Lyu2007-8-24, PM I have never used these so-called patches, and the download speed is basically full. I always thought I had a good RP, haha Keelort2007-8-24, PM Reference (radishli) I used to open 256. After reading this post, I changed it to 50. The result speed has not changed much. I am an 8 m ADSL high ID, and the speed of upstream and downstream traffic changes little. The upstream bandwidth of your ADSL is only 640kb/s. This is a theoretical value and cannot be reached. Therefore, ADSL cannot prove anything. Comrade Xiao Yang Currently, various download software have a small number of semi-open connections { Tagshow (Event) } "> The author of the tool can see the cloud BS software author Trotters in battlefield I understand that it is faster to find the source when the number of half-open connections is large. Fuzzier2007-8-25, AM Reference (battlefield trotters) I understand that it is faster to find the source when the number of half-open connections is large. No. There are only two ways to find the source: One is through P2P { Tagshow (Event) } "> Server Query (whether eMule, BT or { Tagshow (Event) } "> Thunder server), another is through distributed User Switching (eMule's Kad and BT's DHT ). A semi-open connection initiates a connection to the source after the source is found, but the connection has not yet been fully established. There is no relation between the number of sources and the number of semi-open connections. Fuzzier2007-8-25, AM Reference (keelort) The upstream bandwidth of your ADSL is only 640kb/s. This is a theoretical value and cannot be reached. Therefore, ADSL cannot prove anything. This brother, data interaction is performed on a fully established connection, and the half-open connection is inherently unrelated to the transmission rate. Your network speed is fast. If you want to change it back to 10, will it affect your transmission rate. -- This is the most important thing! For other reasons, the bandwidth of users in Europe and America is generally wider than that in China, but it is rare for them to talk about cracking half-open connections; Domestic cracking on half-open connections { Tagshow (Event) } "> The tutorials are mostly from spam software { Tagshow (Event) } "> Advertisements teach users how to use the built-in cracking options of those software. Finally, Microsoft has been engaged in the software and network fields for decades and has countless research institutes, this common sense is impossible for users to make mistakes. If the operating system performance is low, users are lost, and profits are reduced, it is impossible, but domestic users are too easy to get cheated. Hisenko2007-8-26, PM The landlord is right, especially under Vista. Recently, Vista has installed a patch to crack the number of TCP/IP connections. However, if you open a half-open connection to more than 50 connections, the program will become stuck, after a long time, the device crashes. After verification, you still need to modify it That is ,{ Tagshow (Event) } "> We recommend that you set it to 9 and patch the number of TCP/IP connections to be cracked ~~~ After I tried it, the program will still be stuck in the 50 range. It is better to set it up. If you leave it empty, it may have unexpected results ~ In the same building, if you really want to change it and crack it again, set it to 30, but as you said downstairs, you may not be able to stand it at 25. The most annoying HTTP or other P2P software is that it cannot be set up. It will take a while, so we have to pack the patch back ~ It doesn't matter if you set another 999999. It's just an eye addiction. Foreverbelmont2007-8-26, PM Generally, you do not need to change this type. In XP, if you have to change your hand itch, it should be within 100. P.s .... KitBoy2007-8-26, PM As long as IE is used, there is no need to change it. But if you want to use thunder, BT and other software, you must change it. The number of connections does not matter. Half-Open should be for the entire { Tagshow (Event) } "> For windows, I have observed that As long as you start BT, the BT program will keep occupying your 10 half-open At this time, if you use IE to open the website, it will not be displayed because you cannot get half open and cannot connect to it. Hisenko2007-8-26, PM So it is appropriate to set the number to 9. We encourage you to set the number to 9. Zzm168fafafa2007-8-26, PM Bittegenie is much faster to download. Mingyue drunk, PM Change to 1 to see if there is any change ??? If you do not change the value, the "Maximum number of concurrent connections" message is frequently displayed in the "Event Viewer" It is hard to say how fast the change will take place after the change, because the speed is affected by many factors, However, in my personal experience, when SP2 is set to 10 by default, BT is set to basically { Tagshow (Event) } "> The web page cannot be opened. If it is changed to 200, it is basically not affected. Fuzzier2007-8-28, PM Reference (Moon drunk @, PM) Change to 1 to see if there is any change ??? If you do not change the value, the "Maximum number of concurrent connections" message is frequently displayed in the "Event Viewer" It is hard to say how fast the change will take place after the change, because the speed is affected by many factors, However, in my personal experience, when the default number of SP2 is 10, the basic web page cannot be opened when bt is down. If it is changed to 200, the basic web page will not be affected. This dude prefers to go to extremes. EMule and other software are supported by corresponding setting options. You can set the limit to 8 or 9 and then see how? What you call cannot be opened is because of your setup problems. You are too greedy = you cannot get anything. If your software does not support semi-open connection restrictions, contact the developer. P2P software will indeed receive a large number of sources at the beginning of the task, which will occupy all the configured semi-open connections. However, this situation can only be maintained for a few minutes, and then it will rarely obtain new sources, either the maximum number of connections is reached (per task or global), and the number of half-open connections is not used. If the number is not used, it is left { Tagshow (Event) } "> After the browser and other programs, what you call" change to 1 "is that you have nothing to do. As I have said before, limiting the number of half-open connections can effectively prevent DDoS attacks, but it does not lose the transmission rate, so it is not necessary to set it so high. Fuzzier2007-8-28, PM Reference (kitboy @, PM) As long as IE is used, there is no need to change it. But if you want to use thunder, BT and other software, you must change it. The number of connections does not matter. Half-Open should be for the whole windows. I have observed that As long as you start BT, the BT program will keep occupying your 10 half-open At this time, if you use IE to open the website, it will not be displayed because you cannot get half open and cannot connect to it. BT cannot keep occupying 10 half-open limits! Why do you keep occupying resources? Isn't it because you have been getting a large number of new sources during the download? I also need to draft a little bit about bragging. Unless you do not set the half-open limit correctly. UTorrent and bitcomet all have corresponding options. You 'd better take a look. A large number of requests for semi-open connections can only take place in the first few minutes, and there will be no new sources. Poetry and liquor drifting-8-28, PM I don't know. It's almost the same as how much it is set. The key is bandwidth. KitBoy2007-8-29, PM Reference (fuzzier @, PM) Reference (kitboy @, PM) As long as IE is used, there is no need to change it. But if you want to use thunder, BT and other software, you must change it. The number of connections does not matter. Half-Open should be for the whole windows. I have observed that As long as you start BT, the BT program will keep occupying your 10 half-open At this time, if you use IE to open the website, it will not be displayed because you cannot get half open and cannot connect to it. BT cannot keep occupying 10 half-open limits! Why do you keep occupying resources? Isn't it because you have been getting a large number of new sources during the download? I also need to draft a little bit about bragging. Unless you do not set the half-open limit correctly. UTorrent and bitcomet all have corresponding options. You 'd better take a look. A large number of requests for semi-open connections can only take place in the first few minutes, and there will be no new sources. Do you think that thunder and Bt are waiting in the queue as soon as they are in the queue ???? Can be connected and connected. Of course, the software can also set the maximum uTorrent to 8 There are also cats. My maximum is 75. Maybe China Telecom has a limit of 10, which is not enough. Fuzzier2007-8-30, PM Reference (kitboy @, PM) Do you think that thunder and Bt are waiting in the queue as soon as they are in the queue ???? Can be connected and connected. Of course, the software can also set the maximum uTorrent to 8 There are also cats. My maximum is 75. Maybe China Telecom has a limit of 10, which is not enough. How long can you queue? That is, just a few minutes before the task starts. What do you think the new source appears anytime and anywhere. Foreign users seldom say that they are not enough. You don't feel enough, and your mind is very helpful. Thunder was originally a waste, basically the same as domestic software. It was a pity that some people believed in the incorrect concept. RadishLi2007-8-30, PM Which of the following is the most important thing? What is the bandwidth, and the number of semi-open/fully-open configurations? >_< Day ......... Che GUEVARA2007-8-30, PM Not very useful. Ohyes2007-8-30, PM Half-open connections = concurrent connections? Is it a concept for different translations? Thank you! KitBoy2007-8-30, PM Reference (fuzzier @, PM) Reference (kitboy @, PM) Do you think that thunder and Bt are waiting in the queue as soon as they are in the queue ???? Can be connected and connected. Of course, the software can also set the maximum uTorrent to 8 There are also cats. My maximum is 75. Maybe China Telecom has a limit of 10, which is not enough. How long can you queue? That is, just a few minutes before the task starts. What do you think the new source appears anytime and anywhere. Foreign users seldom say that they are not enough. You don't feel enough, and your mind is very helpful. Thunder was originally a waste, basically the same as domestic software. It was a pity that some people believed in the incorrect concept. You can reach the speed limit in just a few minutes. You don't have to look at the webpage or anything. How do you know that foreign countries are not enough? It seems that the half-open attack has also started abroad. In addition to understanding English, what language do you know? It's not up to you to decide whether thunder is spam or not. Moreover, the express train is also learning thunder. Of course, after the purchase RadishLi2007-8-30, PM Reference (kitboy @, PM) As long as IE is used, there is no need to change it. But if you want to use thunder, BT and other software, you must change it. The number of connections does not matter. Half-Open should be for the whole windows. I have observed that As long as you start BT, the BT program will keep occupying your 10 half-open At this time, if you use IE to open the website, it will not be displayed because you cannot get half open and cannot connect to it. Yes, I thought for a moment, it seems like my mom said. In the past, I had to first use the BT downstream sources to divert traffic and then use the Ed upstream { Tagshow (Event) } "> Share So it was at that time that I changed the semi-open data value, or I have never changed any settings when I was using it. Even if I don't have a valid server, every time I open BT, my website will be extended. So I had to modify the semi-open 256... and then I used 256 semi-open data... However, I didn't care about the changes because I didn't seem to have any reference to the changes. Fuzzier2007-8-31, AM Reference (kitboy @, PM) You don't have to look at the webpage or anything. How do you know that foreign countries are not enough? It seems that the half-open attack has also started abroad. In addition to understanding English, what language do you know? It's not up to you to decide whether thunder is spam or not. Moreover, the express train is also learning thunder. Of course, after the purchase Speed limit? Dude, is it good to see my post? This saves you the trouble of opening a yellow box. Can I reach the maximum rate in a few minutes? I am talking about getting a large number of new sources in a few minutes, and there will not be many new sources in the future. After the connection is half open, it will naturally be blank. P2P originally had a queue, and it was only possible to reach the maximum rate in a few minutes. You have never used eMule or Bt in foreign countries. The foreigners seldom talk about half-open cracking, and the downloaded software does not provide any cracking. In other words, some websites that provide optimization guidance are just mentioned. As for the blood-sucking donkeys of thunder and express trains, create one to block and kill one! Spam! I will repeat it again: for Web browsing problems, set the limit { Tagshow (Event) } "> After the problem is solved, your problem is not a problem at all. You are greedy. For upstairs shunting, it is enough to change the XP half-open limit to 50. Baofengzf2007-8-31, PM Now it's a habit Reinstalled systems must be cracked. It was unnecessary. RadishLi2007-8-31, PM Reference (fuzzier @ 2007-8-31, 10: 02 am) Reference (kitboy @, PM) You don't have to look at the webpage or anything. How do you know that foreign countries are not enough? It seems that the half-open attack has also started abroad. In addition to understanding English, what language do you know? It's not up to you to decide whether thunder is spam or not. Moreover, the express train is also learning thunder. Of course, after the purchase Speed limit? Dude, is it good to see my post? This saves you the trouble of opening a yellow box. Can I reach the maximum rate in a few minutes? I am talking about getting a large number of new sources in a few minutes, and there will not be many new sources in the future. After the connection is half open, it will naturally be blank. P2P originally had a queue, and it was only possible to reach the maximum rate in a few minutes. You have never used eMule or Bt in foreign countries. The foreigners seldom talk about half-open cracking, and the downloaded software does not provide any cracking. In other words, some websites that provide optimization guidance are just mentioned. As for the blood-sucking donkeys of thunder and express trains, create one to block and kill one! Spam! I will repeat it again: the problem of browsing the Web page is solved by setting a half-open limit. Your problem is not a problem at all, but you are too greedy. For upstairs shunting, it is enough to change the XP half-open limit to 50. 50 Then I will change it, and I will give a friendly reminder. Round eulb2007-8-31, PM Reference (fuzzier @, am) Reference (keelort) The upstream bandwidth of your ADSL is only 640kb/s. This is a theoretical value and cannot be reached. Therefore, ADSL cannot prove anything. This brother, data interaction is performed on a fully established connection, and the half-open connection is inherently unrelated to the transmission rate. Your network speed is fast. If you want to change it back to 10, will it affect your transmission rate. -- This is the most important thing! For other reasons, the bandwidth of users in Europe and America is generally wider than that in China, but it is rare for them to talk about cracking half-open connections. Domestic tutorials on cracking half-open connections, most of them come from spam software and advertise themselves to teach users how to use the built-in cracking options of those software. Finally, Microsoft has been engaged in numerous research institutes in the software and network circles for decades, this common sense is impossible for users to make mistakes. If the operating system performance is low, users are lost, and profits are reduced, it is impossible, but domestic users are too easy to get cheated. I just went to the Microsoft homepage and turned it over. My original understanding/"Restrictions on concurrent connections/" is misleading It should be/"limited number of simultaneous incomplete outbound TCP connection attempts /" Ref: { Checkurl (this. href); Return false; } "Href =" http://technet.microsoft.com/en-us/library...57156.aspx#EHAA "target =" _ blank "> http://technet.microsoft.com/en-us/library...57156.aspx#EHAA Thank you for your questions. PS. In fact, eMule has built the patch { Checkurl (this. href); Return false; } "Href =" http://bbs.verycd.com/topics/334324/ "target =" _ blank "> http://bbs.VeryCD.com/topics/334324/ Keelort2007-9-8, PM It is better to change the number of half-open connections. If I open a scanner, the default thread is 100. I don't want to check the web page at the beginning. If I change the number of half-open connections, there will be no problem.