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What does changing the number of packets sent during the initial congestion window to 10 have on LAN connections?

Via:

ip route change default via GATEWAY dev INTERFACE initcwnd 10 initrwnd 10

Is this advisable / inadvisable for high speed (1gbit) LAN connections?

Does this even have any affect for high speed LAN based connections?

What I mean by LAN connections is LAN Box <-> LAN Box. Communication that never sees 'the internet'.

Thanks!

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Since this is an optimization for high bandwidth, high latency connections, not much. –  Michael Hampton Mar 22 '13 at 8:34

1 Answer 1

IW10 would always speed-up TCP connections during their slow-start phase (initially) but whether that would be noticeable in the context of how much data will be transmitted overall is another question.

IW10 is especially useful for short-lived TCP connections such as those opened by web browsers to load a web page. There are negligible benefits for long-lived connections transmitting a lot of data, such as transferring a big file using HTTP or FTP.

In your case the bandwidth is not a factor to consider. It's the latency that's important. Do a ping and check your round-trip time for the link, it would probably be 1ms or less. If so - there won't be any noticeable benefit.

In general it depends on what you would use those TCP connections for. If you are trying to achieve some form of "real-time" communication between the two hosts and you will be sending more than a couple kilobytes of data (even though the connection enjoys high bandwidth and low latency) - a couple of milliseconds may count.

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