What's the meaning of Nginx variables of "$tcpinfo_rtt, $tcpinfo_rttvar, $tcpinfo_snd_cwnd, $tcpinfo_rcv_space"

[yanqun sun]

Hi,  I will read this article and get understand what tcpinfo_rtt is.
Thank you very much!

2016-12-16 16:15 GMT+08:00 Ruslan Ermilov <ru at nginx.com>:

> On Fri, Dec 16, 2016 at 03:09:14PM +0800, yanqun sun wrote:
> > Hi, all:
> >   I want to get the network latency between the users and my Nginx
> servers
> > on tcp layer. I searched about this and found several Nginx variables
> > bellow:
> >
> > $tcpinfo_rtt, $tcpinfo_rttvar, $tcpinfo_snd_cwnd, $tcpinfo_rcv_space
> > information about the client TCP connection; available on systems that
> > support the TCP_INFO socket option
> >
> >
> >   So does anybody can make an explanation for those variables?
> >   I think *$tcpinfo_rtt* probably means the round trip time from the
> client
> > to the server on tcp layer.
> >   and what about the rttvar, snd_cwnd and rcv_space?
>
> http://linuxgazette.net/136/pfeiffer.html
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