TCP TIME_WAIT问题 [英] TCP TIME_WAIT problem

问题描述

我已经阅读了TCP和套接字编程书。我有一个问题，

I have read a TCP and socket programming book. I have a question,

本书说，TCP的TIME_WAIT状态应保持2MSL时间段为
。但是如何像应用程序
这样的互联网探索没有这个问题？

The TIME_WAIT state of the TCP should remain 2MSL time period as the book said. But how then a internet explore like application does not have this problem?

根据文档，它是4分钟，但在Internet探索
我不需要等待10秒才能刷新网页？

According to the documentation, it's 4 minutes , but in Internet explore I don't have to wait even 10 seconds to refresh a web page?

这是如何运作的？我很困惑请解释。

How this works? I'm confused please explain.

推荐答案

有几种可能性，其中一些我在下面列出。

There are a few possibilities, some of which I've listed below.

首先，并非所有会话都通过 TIME_WAIT 状态。如果另一方关闭连接，则本地转换为 ESTABLISHED ， CLOSE_WAIT ， LAST_ACK 和 CLOSED ，因此没有涉及 TIME_WAIT 。

The first is that not all sessions move through the TIME_WAIT state at all. If the other side closes the connection, the local transitions are ESTABLISHED, CLOSE_WAIT, LAST_ACK and CLOSED, so there's no TIME_WAIT involved.

其次， TIME_WAIT 状态适用于会话，这是一个5元组 {协议，source-ip，source-port，dest-ip，dest-port} 。

Secondly, the TIME_WAIT state applies to a session, which is a 5-tuple {protocol,source-ip,source-port,dest-ip,dest-port}.

如果任何这些值会在下一个会话（通常是源端口）中发生变化，不受前一个会话的影响。

If any of those values change for the next session (usually source-port), that's unaffected by the previous session.

最后，浏览器没有在每个请求后关闭会话。为了重新使用它们，更有可能（为了提高效率）维护一个开放会话池，例如当你想要下载一个包含50个图像（一个会话而不是五十个）的页面时。

Lastly, the browser doesn't have to shut down the session after each request. It's more likely (for efficiency) to maintain a pool of open sessions in order to re-use them, such as when you want to download a page with fifty images (one session rather than fifty one).

它甚至可以在页面完全加载后打开这些会话，因为你有可能访问该服务器上的其他内容。

It can even leave such sessions open after a page is fully loaded, on the off-chance you'll access something else on that server.

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