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jgraback

join:2011-07-25
Portland, ME

[Tweak Test] RWIN tweak results for GWI.net ADSL (7 Mbps connect

Last night I ran a series of DSL tweak tests (from this site) at different RWIN settings, after getting a free speed upgrade from 3 Mbps to 7 Mbps from my ISP, Great Works Internet, in Portland, Maine. My objective was to see how much the data throughput really did vary with changes in the RWIN setting in the Windows registry, and to find the optimum RWIN setting for my particular 7 Mbps broadband connection, which is via a 10 Mbps Ethernet connection to the simple Westell WireSpeed ADSL modem that my ISP supplied about 5 years ago. I'm about a mile up the street from the Telco's big downtown switching center.

An Excel table and chart of the results, as well as a copy of the optimum results I got at an RWIN setting of 67500, is attached, for general info. The bottom line is that I was able to nearly double my data throughput rate by adjusting RWIN from my Win 2K default value of 17160 up to 65700. (The blip in the curve between the RWIN settings of 65535 and 67500 [which was given as my minimum recommended setting in the tweak test results I got, BTW] probably has to do with "Window Scaling" coming into play at values above 65535). I also ran several speed tests (using the java applet) at various RWIN settings, using the connection to Speakeasy.net in New York City (linked on this site); the results were almost all right around 6.15 Mbps download and 0.61 Mbps upload (a little slower at the very lowest RWIN settings). And I ran a line test on my phone line, which showed 0% line loss and 63.7 ms latency. I'm not requesting any assistance here, so hopefully that's enough relevant info.

For these tests I used my old Dell Dimension 4100 Pentium III 1.0 GHz computer (w/512 MB of RAM) running Windows 2000 Pro SP4 w/MSIE 6 SP1 - since at first I wasn't really sure what I was doing and I didn't want to risk messing up my "real" computer, a Dell Precision WS 390 Core 2 Duo (w/2 GB of RAM) running Windows XP Pro SP3 w/MSIE 8 - but I assume the results I got will generally apply to my current computer also (although the actual throughput speeds I get may be somewhat different).

Hope some people find this of interest!

jgraback

join:2011-07-25
Portland, ME

Re: [Tweak Test] RWIN tweak results for GWI.net ADSL (7 Mbps con

Just an update from the original poster: I'm getting similar or slightly slower throughput results after setting RWIN=65700 in Windows XP Pro SP3 on my much faster Dell Precision WS 390 computer (see the next-to-last last paragraph of my above post for specs). I'm assuming this RWIN value is optimum for this computer also - but it might not be. I haven't done a complete series of tests with this machine like I did before.

The original series of tests I ran were quite time-consuming, as you have to reboot and then re-test every time you change the RWIN value. Anyway, I consider the throughputs I'm getting (see attached Tweak test result) to be fast enough. I can download a 1 MB file in a little less than 2 seconds!

jgraback

join:2011-07-25
Portland, ME
reply to jgraback

I just noticed that I transposed some digits in my original post: My optimum RWIN setting is 65700, not 67500 (occurs twice in the 2nd paragraph). Sorry about that!

The correct RWIN value of 65700 is shown in the attached test results.



Irish Shark
Play Like A Champion Today
Premium,MVM
join:2000-07-29
Las Vegas, NV
kudos:4
reply to jgraback

Your initial RWIN of 17160 is close to the default RWIN for that OS. It is too low for a 7mb line, but may be OK for a 3mb line.

For a 7mb line I would suggest an RWIN of 63888. You want the lowest RWIN that gives you the most consistent speed without errors.

The difference between 65700 and 67500 is not significant. Your speed should be about the same. One speed test will not prove or disprove what RWIN is "better". Run 10 speed tests to the same sight for each RWIN and see what you get.

Try this and see what you get:

Download DrTcp

Set Tcp Receive Window to 63888

Set Windows Scaling, Time Stamping, Selective Acks, Path MTU Discovery, Black Hole Detection to Default.

Leave Max Duplicate Acks and TTL Blank

Using the drop-down menu in The Doctor set your NIC’s (Ethernet adapter’s) MTU to 1492.

Save/Exit DrTcp

Reboot

Rerun the Tweak Test

Run Two Speed Tests from the two DIFFERENT cities nearest to you that are listed here: Speakeasy POPs

Also, test here »ftp://ftp1.optonline.net/test512

Note your transfer rate after about 30 seconds. Then cancel the download.

Post the URL for the New Tweak Test. For the TWO Speakeasy Tests, Copy and Paste the speed results from those tests and note the speed from the FTP download test.
--
"You can observe a lot by watching". Yogi Berra



Irish Shark
Play Like A Champion Today
Premium,MVM
join:2000-07-29
Las Vegas, NV
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reply to jgraback

Max packet sent (MTU): 1500
Max packet recd (MTU): 1470

From your Tweak Test, there is a MTU mismatch between the registry (your Box) and your router.
--
"You can observe a lot by watching". Yogi Berra


jgraback

join:2011-07-25
Portland, ME
reply to Irish Shark

downloadDSL Tweak Re···.mht.zip 67,733 bytes
Baseline test
downloadDSL Tweak Re···.mht.zip 30,618 bytes
New test
Irish, I'm sorry I haven't responded to your reply to my original post more quickly; I've just been busy and haven't had time to run more tests. Thanks for the input!

But early this evening I did reset my RWIN in Windows XP Pro SP3 to 63888, and made the other changes you suggested above, then rebooted and re-ran the Tweak Test. A copy of the results are attached, along with a copy of a baseline test I ran first, with my old settings. As you can see by comparing the two test results, I did get a small increase in throughput when I lowered RWIN from 65700 to 63888.

I also set MTU to 1492 for my Ethernet controller, as you suggested, but I'm still seeing the same mismatch between my actual sent and received MTU's in the test results, just as before. I don't know of any way to change the MTU setting (or any other settings) on my basic ISP-supplied Westell WireSpeed ADSL modem, if that's what you were implying in your second reply post.

If you still need the URL for the original copy of the re-test that's on your server, it's:
»/tweakr/block:···a=normal

Also, I did run the two speed tests on www.speakeasy.net that you suggested, with the following results:
To New York, NY:
Download Speed: 5861 kbps (732.6 KB/sec transfer rate)
Upload Speed: 676 kbps (84.5 KB/sec transfer rate)
To Washington, D.C.:
Download Speed: 5734 kbps (716.8 KB/sec transfer rate)
Upload Speed: 676 kbps (84.5 KB/sec transfer rate)
I also ran a second set of speed tests, with pretty similar results.

Finally, I performed the download test that you suggested; after about 30 seconds, the file download speed was 714KB/Sec., and seemed pretty stable. That's a pretty impressive file download speed, I think! Probably not too many servers can keep up with that kind of throughput.

So let me know what you think of these results. I'm quite pleased, especially since the speed upgrade I recently got from GWI didn't cost me anything! They're a good ISP, and they also bundle a nice land-line phone service package in with broadband internet service (unlimited LD dialing, etc.), all for about $70 a month!

Great Works Internet was awarded a major federal stimulus grant last year, to help pay for constructing a new fiber-optic network backbone (called the "Three Ring Binder") throughout most of Maine, to enable the delivery of HS internet service (up to 20 Mbps!) to both urban and rural areas of the state. Now they've just partnered with Sidera Networks to link Maine's new Three Ring Binder network directly with Sidera's major HS nodes in Boston and New York, which in effect ties this rather remote, mostly rural state directly into the national HS network backbone. There's more info on all this stuff on GWI's website at: »www.gwi.net/policy/news/ - if anyone's interested.


Irish Shark
Play Like A Champion Today
Premium,MVM
join:2000-07-29
Las Vegas, NV
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1 edit

• What is the model number of your MODEM?

• Do have a Router?

• Are you using PPPoE or PPPoA?

• Let's see if we can determine your ISP's MTU:

The value you should use for your MTU setting is dependant on the MTU value for your ISP since all packets (data) will be travelling through their servers.

To determine the maximum MTU value for your ISP, open a DOS/Command Prompt window and type :

ping -f -l [packet size] [your www.isp's url or IP address]

(Start with a packet size of 1472. Use 98.129.229.182 or www.gwi.net for your isp entry.

Where [packet size] is the amount of data you want to send (range is 0 - 1500) and [www.your isp url] is the url of your ISP.

Your ISP's MTU is determined from the largest packet size value that does not return the error "Packet needs to be fragmented but DF set"

Then reduce 1472 by 10 until you no longer get the "packet needs to be fragmented" error message. Then increase by 1 until you are 1 less away from getting the "packet need to be fragmented" message again.

Add 28 more to this (since you specified ping packet size, not including IP/ICMP header of 28 bytes), and this is your MaxMTU.

If you can ping through with the number at 1472, you are done! Stop right there. Add 28 and your MaxMTU is 1500.

• Once we can determine what your MTU is then we can set the MTU in the registry and in your MODEM or Router.
--
"You can observe a lot by watching". Yogi Berra



Irish Shark
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reply to jgraback

Click for full size
Is this your MODEM?

jgraback

join:2011-07-25
Portland, ME
reply to Irish Shark

Irish, the actual Model Number of my ISP-supplied Westell WireSpeed ADSL Modem is C90-36R516-01, Rev. H. It was manufactured in January 2002. Yesterday I found the User Guide for it online, and downloaded it; the cover is the same as the one you show in your latest reply post. I noted in the description that the maximum design download speed for this modem is 8 Mbps, and the max. upload speed is 800 Kbps - so I'm getting pretty close to maxing out this modem with the speeds I have now.

I do NOT have a router - yet (I do have a simple D-Link Model DSS-8 Ethernet switch, but normally I don't use it). I may purchase a combination ADSL modem and router, with built-in firewall, at some point. I'm planning on getting an HD TV and/or Blue-Ray Player with an Internet connection later this fall or winter, so at that point I will really need the ADSL modem/router with built-in firewall. Currently, I just have the on-board Ethernet controller in my PC directly connected to the Westell WireSpeed ADSL modem, via a short Cat 5 Ethernet cable. And I'm using the software firewall built into Windows XP SP3.

I asked GWI technical support about my Point-to-Point Protocol. They said that GWI doesn't use PPP at all; instead they use DHCP, like a cable modem would normally use (and in the "Status" window for the Ethernet connection to my ADSL modem, on the "Support" tab, I notice it says "Address Type: Assigned by DHCP"). They also said that I cannot change any settings to the ADSL modem that they supplied. They use an MTU setting of 1472, so they indicated that optimally I should use that MTU setting in Windows, to match the modem setting (that's what it's set at now, but we're still seeing the small Max Packet MTU mismatch between upload and download results in your Tweak Test).

But before I talked to GWI, I ran the Ping test at 1472 as you requested, and got no "packet needs to be fragmented" error message - so I guess that just confirms that GWI is using 1472 as their MTU setting, right? Anyway, here are the actual results of the Ping test, as copied right from my DOS window:

"Pinging 98.129.229.182 with 1472 bytes of data:

Reply from 98.129.229.182: bytes=1472 time=77ms TTL=50
Reply from 98.129.229.182: bytes=1472 time=78ms TTL=50
Reply from 98.129.229.182: bytes=1472 time=77ms TTL=50
Reply from 98.129.229.182: bytes=1472 time=78ms TTL=50

Ping statistics for 98.129.229.182:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 77ms, Maximum = 78ms, Average = 77ms"

So I guess the only question remaining is: Should my actual MTU setting in Windows be 1472 or 1500 (in other words, should the setting include the 28 bytes for the header, or not)? It probably doesn't make that much difference, but we might as well get the optimum setting.

BTW, when I talked to GWI Tech Support, we also discussed my existing line status, which they can and do monitor. They said that I'm actually only about 3800 ft. (round trip, which is how they measure it) from the nearest neighborhood switching station here in downtown Portland - not a mile or so (one way), as I previously thought. But I'm in a 40-year-old high-rise apartment building, which undoubtedly still has its original telephone system wiring. And who knows how old the copper telephone wire is out on the utility poles? Anyway, they said that my line noise currently limits my practical maximum download speed to about 6.1 Mbps, which is about what I'm getting now (they said my theoretical maximum is about 6.7 Mpbs). So even if I tried to upgrade to their more expensive 20 Mpbs service (which I don't need anyway), I probably wouldn't see any significant real-world speed increase.

Hope you find all of this of interest. Let me know if you have any other feedback for me. If you tell me to tweak my Windows MTU setting again, I'll run a final pair of Tweak tests (baseline and re-test, with the new setting). Thanks for all of your input!

Jon



Irish Shark
Play Like A Champion Today
Premium,MVM
join:2000-07-29
Las Vegas, NV
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Yes, some ADSL/others provides DHCP connection. This is what cable ISPs use and Verizon FIOS (not sure this is all areas yet).

The MTU is 1500.

I am not sure if the GWI rep gave you the MTU with out the overhead of 28 bytes. With your ping tests, the 1472 is 1472 + 24 = 1500 MTU. That should be correct.

One why to find out is to ping 1473 and see if you get the frag message.

The MODEM is old, and yes, it will hamper your speeds. However, with you connection, the noise most likely cannot be fixed. You might want to ask the supper if GWI can run you some new wires.

Have you looked at any cable ISP?
--
"You can observe a lot by watching". Yogi Berra