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如何在 Linux 中测量 TCP 连接时间

tag-icon • tag-icon performance tcp
如何在 Linux 中测量 TCP 连接时间

我想测量创建 TCP 连接的开销。

我知道很多像hping和这样的工具netperf，但它们似乎侧重于测量延迟。

我想知道三次握手需要多长时间，分配缓冲区等，然后关闭它。所以我想打开一个真实、合法的 TCP 连接，然后关闭它。

是否有任何工具可以做到这一点并帮助我衡量绩效？

答案1

我认为您要问的是如何测量 TCP 连接上从第一个 SYN 数据包到第一个非零有效负载数据包所需的时间？

在这方面，Tcpdump 是一个很有用的工具，而 Theo Schlossnagle 则书面如何实现这一点。我已经使用了他描述的技术，效果很好。

答案2

对于简单的情况，curl使用该-w选项可以打印这些操作所花费的时间。

Curl 只会打印从一开始的累计时间，因此您必须自己减去这些数字。由于 tcp 连接仅在 dns 查找后启动（假设没有重定向），因此您必须计算time_connect - time_namelookup。我不确定 curl 在进行以下重定向时如何准确测量时间。请注意，这也适用于非 Web 服务，因为 curl 只会在建立 tcp 连接后才发现它不是 http。

示例命令：

$ curl -s -o /dev/null -w "dns:%{time_namelookup}, redir:%{time_redirect}, tcp:{time_connect}\n" poohl.de
dns:0.046345, redir:0.000000, tcp:0.067986

所以建立 tcp 连接的时间是0.067986s - 0.046345s = 0.021641s。

来自手册页：

time_appconnect
    The time, in seconds, it took from the start until the SSL/SSH/etc connect/handshake to the remote host was completed.
time_connect
    The time, in seconds, it took from the start until the TCP connect to the remote host (or proxy) was completed.
time_namelookup
    The time, in seconds, it took from the start until the name resolving was completed.
time_pretransfer
    The  time,  in seconds, it took from the start until the file transfer was just about to begin. This includes all pre-transfer commands and negotiations that are specific to the particular protocol(s) involved.
time_redirect
    The time, in seconds, it took for all redirection steps including name lookup, connect, pretransfer and transfer before the final transaction was  started. time_redirect shows the complete execution time for multiple redirections.
time_starttransfer
    The  time, in seconds, it took from the start until the first byte was just about to be transferred. This includes time_pretransfer and also the time the server needed to calculate the result.
time_total
    The total time, in seconds, that the full operation

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