# Removal of: net.inet.tcp.slowstart_flightsize



## Melvyn (Apr 27, 2014)

Hello,

Reading some guides on network latency to determine the initial payload that FreeBSD can send in the first round-trip and to my surprise net.inet.tcp.slowstart_flightsize is not available on my 9.2-p3. Is this tunable removed or do I need a specific option? I've already tried `sysctl net |grep slow` to see if it was relocated.


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## trh411 (Apr 28, 2014)

This was removed in FreeBSD 9.2. It appears that net.inet.tcp.experimental.initcwnd10 is intended as a replacement, but I cannot find that explicitly stated anywhere. See r242266 - head/sys/netinet for a little background and reference to the IETF TCPM draft letter Increasing TCP's Initial Window. There is also a more recent draft letter on that same site.


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## Melvyn (May 3, 2014)

Thanks. So that would mean, that we also have an initial payload of ~14kB in which we should send the above the fold content for mobile sites (which is what I was researching).


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## trh411 (May 5, 2014)

I read an article recently, on a site I cannot now cite due to memory constraints, that specified 15kB as the "ideal" initial payload size for above the fold content for mobile sites, so your 14kB payload would work well I should think.


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