RcWin behind a router

J-F · Post by **J-F** » Tue Feb 26, 2002 1:43 pm

ADSL PPPoE
Router RT314 with MTU of 1492 (I've programmed it in)
PCs connected to the router have their MTU at 1500 (Per Bob Carrick's recommendation)

Now the stupid question : Does the RcWin have to be a multiple of 1452 or 1460 ??

Thanks ...

Lobo · Post by **Lobo** » Tue Feb 26, 2002 2:44 pm

Yes RWIN is always supposed to be multiple of MSS

If both puters are PPPoE then I would use MTU of 1492 for both so router works.

J-F · Post by **J-F** » Tue Feb 26, 2002 6:17 pm

Lobo, I was not clear enough, sorry

>Yes RWIN is always supposed to be multiple of MSS

Yes, I know that ...

>If both puters are PPPoE then I would use MTU of 1492 for both >so router works.

The router has its own MTU to 1492 but behind the router, the PCs have their MTU to 1500 as this is a Lan ...
The question is: do I have to put the RcWin of the PCs at (1492-40) x X or (1500-40) x X

Lobo · Post by **Lobo** » Tue Feb 26, 2002 6:20 pm

Does your router have lastest firmware upgrade from web site, I never heard of a PPPoE connection with MTU of 150:)

J-F · Post by **J-F** » Tue Feb 26, 2002 6:27 pm

> Does your router have lastest firmware upgrade from web site, I never heard of a PPPoE connection with MTU of 1500

Hmmmm,
My Netgeat RT314 has the latest firmware 3.25 with a MTU of 1492 .... BUT, again, based on B. Carrick's recommendation, the MTU of the puters behind the router has been set up at 1500

Lobo · Post by **Lobo** » Tue Feb 26, 2002 6:28 pm

If you select your connection type at top, it should set MTU to 1492, put this on both puters, then try recieve windows of 31944 or 63888

Download SG Optimizer to your desktop, select connection type at top, select optimal settings at bottom, Select adapter you are using, click on apply changes at very bottom,and REBOOT .
If you wish to enter custom TCP recieve window select custom settings at bottom, enter what you wish, click on apply changes at bottom and REBOOT.
If using Cablenuts adjuster too, you must first bring up adjuster, click on delete Cablenut Tweaks at bottom and reboot, then download and install optimizer.

Optimizer in my signature

Do your speed tests here after you turn off all running programs http://www.speakeasy.net/main.php?page=sup_pops , select site nearest to you, turn everything off thats running, Check Taskbar, 1 browser, clear cache, If you are from over seas select from here: http://www.testmyspeed.com/internationalspeedtests.htm

Even though it is not the nearest the Dallas test is pretty quick

BEFORE SPEEDTEST
1.) Make sure defrag has been run, defragmented files slow you down.
2. At top of IE, click on Tools, internet options, click on delete files and click on offline files (It's safe), click on clear history, yes
3.) Go to Start button, programs, accessories, system tools, disk cleanup, Click OK (Safe)
4.) Run scandisk (Short version)
5.) Scandisk on XP?
Click on My Computer, select Drive that XP is on, RIGHT click on BLANK place, select properties, then tools at top tab, click check now, check box automattically fix system errors, click start,
then test. Turn all running programs off. Reboot computer so you have all your RAM

J-F · Post by **J-F** » Wed Feb 27, 2002 10:24 am

Thks Lobo
But that was not my question
Nevermind

earthmofo · Post by **earthmofo** » Wed Feb 27, 2002 11:34 am

J-F, take the TCP Analyzer test located at the top of this forum. It should show what your current RWIN is as well as the routers MTU. If the RWIN is not a multipule of MSS then make it so.

J-F · Post by **J-F** » Wed Feb 27, 2002 11:51 am

Well, this is not easy when english is not your native language

I know all what you're saying
Once again, the router has its MTU set to 1492
Puters behind the router have their own MTU set to 1500 (per Bob Carrick's recommendation)

Allright ?

The simple question : in such a configuration do I put on the puters an RcWin that will be a multiple of 1492-40 or a multiple of 1500-40

Please tell me yoo see what I mean

earthmofo · Post by **earthmofo** » Wed Feb 27, 2002 12:00 pm

Take this test: http://forums.speedguide.net:8117/

Copy and paste the results here in a reply to this thread. Please X out your IP address. With this information I can tell you what it should be set to.

J-F · Post by **J-F** » Wed Feb 27, 2002 12:09 pm

TCP options string = 020405ac0103030201010402

MTU = 1492
MTU seems to be optimized for PPPoE... If you are not on a PPPoE connection, consider increasing your MTU to 1500 for optimal throughput.

MSS = 1452
Maximum useful data in each packet = 1452, which is equal to MSS.
MSS is optimized for PPPoE. If you are not on a PPPoE connection, consider increasing your MTU value.

Default Receive Window (RWIN) = 255552
RWIN Scaling (RFC1323) = 2 bits
Unscaled Receive Window = 63888
RWIN is a multiple of MSS
Other values for RWIN that might work well with your current MTU/MSS:
511104 (MSS x 44 * scale factor of 8)
127776 (MSS x 44 * scale factor of 2)
63888 (MSS x 44)

bandwidth * delay product:
Your RcvWindow limits you to: 10222.08 kbps (1277.76 KBytes/s) @ 200ms
Your RcvWindow limits you to: 4088.832 kbps (511.104 KBytes/s) @ 500ms

MTU Discovery (RFC1191) = ON

Time to live left = 44 hops
TTL value is ok.

Timestamps (RFC1323) = OFF

Selective Acknowledgements (RFC2018) = ON

IP type of service field (RFC1349)= 00000000

J-F · Post by **J-F** » Wed Feb 27, 2002 12:11 pm

ADSL / PPPoE 512/128
PII-450 384 Mb Ram
Win2000

earthmofo · Post by **earthmofo** » Wed Feb 27, 2002 12:25 pm

Originally posted by J-F
TCP options string = 020405ac0103030201010402

MTU = 1492
MTU seems to be optimized for PPPoE... If you are not on a PPPoE connection, consider increasing your MTU to 1500 for optimal throughput.

MSS = 1452
Maximum useful data in each packet = 1452, which is equal to MSS.
MSS is optimized for PPPoE. If you are not on a PPPoE connection, consider increasing your MTU value.

Default Receive Window (RWIN) = 255552
RWIN Scaling (RFC1323) = 2 bits
Unscaled Receive Window = 63888
RWIN is a multiple of MSS
Other values for RWIN that might work well with your current MTU/MSS:
511104 (MSS x 44 * scale factor of 8)
127776 (MSS x 44 * scale factor of 2)
63888 (MSS x 44)

MTU is reported as your router's value of 1492. RWIN is reported as a multipule of MSS.

Is the RWIN value being reported (255552) the one you have currently on your computer?

J-F · Post by **J-F** » Wed Feb 27, 2002 12:28 pm

> Is the RWIN value being reported (255552) the one you have currently on your computer?

Yes (I've used Optimizer and Cablenut)
Should I lower it or maintain it as it is ?

Thank you by the way

Lobo · Post by **Lobo** » Wed Feb 27, 2002 12:31 pm

31944 or 63888

J-F · Post by **J-F** » Wed Feb 27, 2002 12:36 pm

OK Lobo and Earthmofo, thank you
I'll give both values a try and will stick to the one that will give me the best D/L speed
Sorry again for my bad english

earthmofo · Post by **earthmofo** » Wed Feb 27, 2002 12:38 pm

How are your current speeds compaired to your service caps? IF you're getting 90% of your capped speed then I wouldn't change a thing.

Lobo · Post by **Lobo** » Wed Feb 27, 2002 12:39 pm

Test at site nearest to you from here:

http://www.testmyspeed.com/internationalspeedtests.htm

J-F · Post by **J-F** » Wed Feb 27, 2002 1:27 pm

>How are your current speeds compaired to your service caps? IF you're getting 90% of your capped speed then I wouldn't change a thing.

I'm at the max almost all the time (well, 512 Kb/s is not that much

)

Kirby Smith · Post by **Kirby Smith** » Wed Feb 27, 2002 5:43 pm

If I understand the conclusions of the Nexland router flail we had here recently, then the following is true. If your PCs are at 1500 and your router is at 1492, then, for most low-cost routers, you will get fragmentation on uploaded WAN data. LAN data rate will be maximized, and downloaded WAN data will just not completely fill the packet limit of the PCs. Unless you are uploading data a lot, your original MTU sizes should be OK. If you want to avoid all fragmentation, then all MTUs should be 1492.

kirby