On linux you can run ss -i dst and get the following:

Netid  State      Recv-Q Send-Q Local Address:Port                 Peer Address:Port
tcp    ESTAB      0      0      
         cubic wscale:8,4 rto:202 rtt:1.218/1.927 ato:54 mss:1448 rcvmss:1448 advmss:1448 cwnd:212 ssthresh:259 bytes_acked:2130715165
09 bytes_received:1613981362016 send 2016.3Mbps lastsnd:39 lastrcv:33 lastack:33 pacing_rate 4031.3Mbps retrans:0/4180 reordering:14 r
cv_rtt:18.875 rcv_space:1413168

This gives all of the currently used values of things like congestion window and slow start threshold for a given tcp session.

These values change dynamically over the life of the tcp session.

I have seen Get-NetTCPSetting which gives me information on what windows will use as the starting value for some of these properties but neither it nor Get-NetTCPConnection seem to be able to provide this information.

Is there any way to see this information for a currently active (Established) tcp connection on windows?

  • Run Wireshark, Microsoft Network Monitor, Microsoft Message Analyzer, or the capture program of your choice. – joeqwerty Nov 28 '18 at 19:21
  • @joeqwerty As an example, while you could try to infer the value of something like the slow start threshold at any given point in time from the graph of the data in wireshark you would still not actually know what value the OS is using for that at any given point in time and that is the same for other properties of the tcp session as well which is why I believe a packet analysis tool is insufficient unless I am missing something. – Chris Magnuson Nov 28 '18 at 19:28

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