Irish Shark
Play Like A Champion Today
Premium,MVM
join:2000-07-29
Las Vegas, NV
| reply to Tradewind
Re: [OOL] (POLL) - What RWIN?
You are correct that there is not much of a difference.
When tweaking you want the lowest RWIN that gives you the best, most consistent speeds without errors.
I was working with a gent in the Tweaks Forum who was on a 100mb school line. His RWIN was 64240 and he was pulling 50+mb down. Higher RWINs did not help.
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2 edits | said by Irish Shark  :You are correct that there is not much of a difference. When tweaking you want the lowest RWIN that gives you the best, most consistent speeds without errors. I was working with a gent in the Tweaks Forum who was on a 100mb school line. His RWIN was 64240 and he was pulling 50+mb down. Higher RWINs did not help. Probably not true if he was downloading from a distant server.
The RWIN and ping times are related so that 64240 might get him max speed from a server with a 20ms ping, but not with a 100ms ping.
I'd have to dig up the formula, but it's over in the tweaks forum.
I think the optimum thing is to take your max speed, assume about a 75-100ms ping time (so that you can get top speed cross-country) and calculate your RWIN from that.
EDIT: Found it.
OOL standard max speed is 15mbps, let's assume you want max speed at up to 100ms latency.
RWIN=15,000,000bits/sec * .1sec = 1,500,000 bits = 187,500 bytes.
Since the theory is that it may help to make it a multiple of the MSS, the next multiple up would be 192,720.
As Irish Shark pointed out, you want the lowest RWIN that gives you max speed.
Anything over 192,720 is pretty much a waste at 15Mbps unless you download from servers with a higher than 100ms latency often. |
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Irish Shark
Play Like A Champion Today
Premium,MVM
join:2000-07-29
Las Vegas, NV
| Q: Is there an easier way to calculate my RWIN? (#6181)
A: Well, maybe.
It involves clicking the "more details" portion of the tweak test result, and looking down at the bottom right hand side for an entry saying "RTTavg".
Take this value and use it for latency in the formula.
(latency) x 1.5 x (advertised speed in kbps) divide by 8
Example: MSS is 1460, RTTavg is 125ms, and advertised download speed is 1500kbps.
125 x 1.5 = 187.5
187.5 x 1500kbps = 281250
281250 divide by 8 = 35156
35156 divide by 1460 (MSS) = 24.07
Round up to next even number = 26
26 x 1460 = 37960 (Optimal RWIN).
The problem with this is that you are chasing your tail. When you insert the "perfect RWIN" and run a new Tweak Test, the average RTT changes. So recompute and you will get a new "Perfect RWIN".
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"You can observe a lot by watching". Yogi Berra |
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