Help with Optimal RWIN for me!

[sixdog]

Hi all,

This is my first post here and I am very new to this broadband thing, so bear with me if I ask some stupid question.

- I am on ADSL with PacBell in Los Angeles.
- They cap me at 768/128 kbps.
- EnterNet 300 v.1.41
-Westell WireSpeed external (non-USB) modem with a Kingston NIC.

OK, My default MTU setting is 1454 and the default RWIN is 65535.

Now my speed is normally about 630/100 kbps. This is about roughly 80% of my capped speed. Which is quite good. But paying $40 a month for it I would like to squeeze out every last drop of it. :D :D

My questions are:

#1) Am I right to assume that raising the MTU from 1454 to 1494 will only give me very little if any boost?

#2) My understanding of RWIN is that the higher the better up to a point and after that it will become a hindrance. Is it correct?
Well, I used the Tweak Test at DSL Reports.com. It suggest me to lower my RWIN to 19796. It seems very low to me. But it does seems to me that pages do load up faster after I change it. But the speed test remain pretty much the same.
Now, if I don't get re-transmission and packet loss, will keeping the 65535 be helping or actually hurting the speed?

#3) The TCP/IP Analyser here said that my RWIN limits me to 791.84 kbps @ 200ms. What does that "@ 200ms" mean? Is it referring to the latency?

BTW, here is the Tweak Test done at this site with the 19796 RWIN:
MainCable ModemsDiscussionWindows 9xReviewsEditorialsInformationTweaks & PatchesSG TCP/IP AnalyzerSetting up a LANSecurityBits and BytesInteresting StoriesAutologin with RRCable/DSL FAQTerms & DefinitionsCable / DSL LinksGeneral ForumComputer HardwareComputer SoftwareProgramming ForumSpeedGuide TeamsSG ContestsClassifiedUser Feedback
Mon Jun 25 22:31:42 2001.



SpeedGuide.net TCP/IP Analyzer

Browser/OS = Mozilla/4.0 (compatible; MSIE 5.5; Windows 98; Win 9x 4.90)

TCP options string = 0204058601010402

MTU = 1454
MTU is not fully optimized for broadband. Consider increasing your MTU to 1500 for better throughput.

MSS = 1414
Maximum useful data in each packet = 1414, which is equal to MSS.
MSS is not fully optimized for broadband (although it might work well for slower connections). Consider increasing your MTU value.

Default Receive Window (RWIN) = 19796
RWIN Scaling (RFC1323) = 0 bits
Unscaled Receive Window = 19796
RWIN is a multiple of MSS
Other values for RWIN that might work well with your current MTU/MSS:
520352 (MSS x 46 * scale factor of 8)
260176 (MSS x 46 * scale factor of 4)
130088 (MSS x 46 * scale factor of 2)
65044 (MSS x 46)

bandwidth * delay product:
Your RcvWindow limits you to: 791.84 kbps (98.98 KBytes/s) @ 200ms
Your RcvWindow limits you to: 316.736 kbps (39.592 KBytes/s) @ 500ms
Consider increasing your RWIN value to optimize TCP/IP for broadband.

MTU Discovery (RFC1191) = ON

Time to live left = 113 hops
TTL value is ok.

Timestamps (RFC1323) = OFF

Selective Acknowledgements (RFC2018) = ON

IP type of service field (RFC1349)= 00000000




292 connections tested since 03.10.2001.
Analyzer version: Beta 0.99

[EvilAjax]

Search the forum for "MaxFrameSize" and you'll learn how to change your MTU to 1492.

[sixdog]

Thanks for the reply.

I knew how to change the MTU, I'm just wondering does such a small change (from 1454 default to 1492 max) will really help or not.
More importantly, I wanna know about the optimal RWIN for me.

[BigAmp]

yes it dose the computer dails with 1492 part of info at one time now , about the old 1454 at a time.

[Lobo]

In help page below in signature, click on DSL in middle of 1st page, then pay attention to MaxFrameSize, the download does not work so you have to dude :) :) :)

[sixdog]

Thanks guys.

Will start tweaking.
Will post back is I have more question. :)