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

[Maxim Konovalov]

Hello,

On 12/16/16 10:09 AM, 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?
> 
I would suggest to check any tcp 101c-like book for the explanation.

-- 
Maxim Konovalov