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Tune high-speed networks for faster transfers
Authored by: regulus on Jun 20, '06 05:41:51AM

I liked this hint and reading the tutorial, thanks. With my set-up it won't help me though. Here's why.

From reading the tutorial it says that you need to calculate the BDP (bandwidth delay product). I have a gigabit ethernet network in my home. The bottleneck on my network would seem to be the firewire 400 connections for my numerous external hard drives connected to my server. All the other connections are faster than the firewire connection i.e. the hard drives, the gige network cards, the gige switch, the cat 6 wiring are all faster than the firewire connection which has a max throughput of 400 Mb/s (ideally). So to calculate the BDP you ping your server (which gives the the RTT) and multiply that by the bottleneck. Pinging my server yielded a time of .264 milli seconds. Therefore my calculation is as follows:

400,000,000 bits/s * 1 Byte/ 8 bit * .264/1000 s = 13,200 Bytes or 13.2 KB

As such the default send/receive window size is more than adequate. The tutorial even states "If the BDP is small either because the link is slow or because the RTT is small (in a LAN, for example), the default configuration is usually adequate."

Testing my speed at the default configuration I get between 22 to 32 megabytes/s from my various 10 external hard drives. Since the ideal firewire speed is 400 Mb/s which yields and ideal speed of 50 MB/s, and knowing that nothing is ideal in the real world, I think I'm OK.

Just to make sure I tested it by adjusting my parameters as suggested and saw no change in my transfer speed on my LAN. As far as my internet connection, I already get around my rated speed from my ISP as tested at broadbandreports.com. Therefore I can only conclude that this hint won't help me.

I'm always looking to tweak my speed, so if anyone sees any fault in my logic please let me know.



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