openssh with HPN patches over a high BDP link

Chris Stankevitz chrisstankevitz at
Mon Aug 24 22:09:32 UTC 2015

I use ssh over a high-BDP WAN link (BDP=1MByte).  tcpdump shows I am
TCP window limited with a max bytes-in-flight of ~64 KBytes (too
small).  I am using the command "# cat /dev/urandom | ssh root at host
'cat > /dev/null'"

Q: Is it true that FreeBSD's base openssh is built with the HPN ssh
patches? (I believe it is true given changelogs and references in

Q: If HPN is indeed enabled, can anyone explain my abysmally small TCP window?

Over the same link with iperf the window opens at ~30 KBytes/sec until
it reaches ~500 KBytes

Thank you,


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