tcp实验

抓包: 两台服务器，一台启动python http服务，上面有一个2G的文件。另一台下载。怎么抓包，在那台机器上抓包，是不是指定来源ip就可以了？是指定抓n个包，还是说指定ip，从开始下载到结束？抓完包后怎么分析，需要分析哪些内容？arp协议？地址询问？http三次握手？三次挥手？怎么调整内核，又要重新抓包？内核调整时，服务器有什么变化，用top命令能看出来么？ rt，丢包率，curl速度怎么查看？使用–help，需要谷歌协助么？执行curl就出问题了

服务端

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server:172.19.5.43
python -m SimpleHTTPServer 8089

ll -h
-rw-r--r--. 1 root root 1.9G Mar 25 11:37 zookeeper.out

客户端

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client:172.19.9.147
tcpdump -i eth0 tcp port 8089 and host 172.19.5.43 -w tcpdump-$(date +%Y-%m-%d-%H-%M-%S).cap
[root@172.19.9.147 ~]# wget http://172.19.5.43:8089/zookeeper.out
--2023-03-26 00:49:47--  http://172.19.5.43:8089/zookeeper.out
Connecting to 172.19.5.43:8089... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1972256747 (1.8G) [application/octet-stream]
Saving to: ‘zookeeper.out’

100%[==========================================================================================================================================>] 1,972,256,747 53.2MB/s   in 25s    

2023-03-26 00:50:11 (76.3 MB/s) - ‘zookeeper.out’ saved [1972256747/1972256747]

[root@172.19.9.147 ~]# curl http://172.19.5.43:8089/zookeeper.out --output zookeeper.out.file
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 1880M  100 1880M    0     0  77.0M      0  0:00:24  0:00:24 --:--:-- 54.3M

curl 控制速度

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[root@172.19.9.147 ~]# curl http://172.19.5.43:8089/zookeeper.out --output zookeeper.out.file --limit-rate 1M
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
 33 1880M   33  625M    0     0  1023k      0  0:31:21  0:10:25  0:20:56  996k

tc命令介绍

BDP和buffer、RT的关系搜这个问题发现别人早就看过任总的文章了，还写了笔记。https://blog.csdn.net/fdsafwagdagadg6576/article/details/121011575

相关概念

BDP: (Bandwidth-Delay Product) 带宽时延积
Buffer: 指的是sysctl中的 rmem或者wmem
rt: tcp的timestamps->time since previous frame in this tcp stream(我猜就是响应时间的一种)

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[root@172.19.5.43 ~]# sysctl -a | grep 'net.ipv4.tcp_wmem'
sysctl: reading key "net.ipv6.conf.all.stable_secret"
net.ipv4.tcp_wmem = 4096        16384   4194304
sysctl: reading key "net.ipv6.conf.default.stable_secret"
sysctl: reading key "net.ipv6.conf.docker0.stable_secret"
sysctl: reading key "net.ipv6.conf.eth0.stable_secret"
sysctl: reading key "net.ipv6.conf.lo.stable_secret"
sysctl: reading key "net.ipv6.conf.veth59705c1.stable_secret"
sysctl: reading key "net.ipv6.conf.veth6cbfe80.stable_secret"
[root@172.19.5.43 ~]# sysctl -a | grep 'net.ipv4.tcp_wmem'
sysctl: reading key "net.ipv6.conf.all.stable_secret"
net.ipv4.tcp_wmem = 4096        4096    4096
sysctl: reading key "net.ipv6.conf.default.stable_secret"
sysctl: reading key "net.ipv6.conf.docker0.stable_secret"
sysctl: reading key "net.ipv6.conf.eth0.stable_secret"
sysctl: reading key "net.ipv6.conf.lo.stable_secret"
sysctl: reading key "net.ipv6.conf.veth59705c1.stable_secret"
sysctl: reading key "net.ipv6.conf.veth6cbfe80.stable_secret"

参数相关

更新了配置后，直接服务也启动失败，wget也异常了。