Resetting MTU for ICS clients on PPPoE DSL

pellizzeri · Post by **pellizzeri** » Tue Jun 26, 2001 5:13 pm

We've been experiencing a problem loading specific web pages (and graphics on some web pages, like E-bay) on our 2 client PCs. These are web pages that load fine on the host and used to load on the clients. I just found this article in MS knowlegebase (http://support.microsoft.com/support/kb ... &SPR=MSALL) and think it addresses my problem, which started about a month ago when I was running some DSL tweaks on all 3 PCs. At that time, I used the analyzer on both of the clients and remember them having an MTU of 1500. My question is, should I follow the directions MS gives for adjusting the MTU on the clients by pinging the host from a DOS prompt, starting with an MTU of 1454 and working my way down (by what increment?), or does someone have a better/simpler method to suggest? Thanks in advance for your help. -kp

Lobo · Post by **Lobo** » Tue Jun 26, 2001 5:35 pm

There are alot of ways but I would just call ISP and ask them what they use then you do the same

PPPoE MTU=1492
MSS=1454

BigAmp · Post by **BigAmp** » Tue Jun 26, 2001 6:13 pm

the ISP will most likely tell you to set the MTU and MSS to the value Lobo said, but go with those.

pellizzeri · Post by **pellizzeri** » Tue Jun 26, 2001 7:05 pm

While my ISP, Pacific Bell, does not prohibit my using ICS with their DSL service, neither do they provide support for it. I'll take your recommendations and set the MTU to 1492 and the MSS to 1454 and see what happens. Can you point me to the right place in the registry or suggest a utility to do this? Thanks again to you both.

gRoUnD_zEr0 · Post by **gRoUnD_zEr0** » Tue Jun 26, 2001 7:50 pm

You will want to Download cablenut's softwareHere ..It's easy to use all you got to do is install, open up Adjuster .exe and change your MTU and MSS values, save to registry and reboot...You might want to think of saving a Registry for back up reasons before you start to tweak (If you do).

pellizzeri · Post by **pellizzeri** » Tue Jun 26, 2001 10:47 pm

Way to go, it worked like a charm!!! Thank you all ever so much!
-kat

gRoUnD_zEr0 · Post by **gRoUnD_zEr0** » Wed Jun 27, 2001 3:06 am

No problem...What are your speeds like now? Faster than before I assume..You might want to post the speedguide TCP/IP Analyzer stuff here so Lobo can get you a better RWIN or someone else for *possible* faster speeds.

pellizzeri · Post by **pellizzeri** » Thu Jun 28, 2001 1:02 pm

After I ran the tweaks on my PCs, I asked PacBell to reprofile our connection and they upped the speed to 768. That worked great for our host and one of the client PCs, but the other client started acting like it was using a 28.8 dialup! After living with that for a couple of weeks, I asked them to bring it back down to 384. They did, and then all of our PCs were able to connect in the 290-360 range. I'm reasonably happy with the connection speed now, especially since I fixed the problem related to MTU, but here are the analyzer results, in case there's something there that's noticeably off. Thanks! -kat
--------------------------------------------------------------------------------
Host PC:
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 = 49 hops
TTL value is ok.

Timestamps (RFC1323) = OFF

Selective Acknowledgements (RFC2018) = ON

IP type of service field (RFC1349)= 00000000
----------------------------------------------------------------------------------
Kitchen Client:
TCP options string = 020405ac01010402

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) = 8712
RWIN Scaling (RFC1323) = 0 bits
Unscaled Receive Window = 8712
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)
255552 (MSS x 44 * scale factor of 4)
127776 (MSS x 44 * scale factor of 2)
63888 (MSS x 44)

bandwidth * delay product:
Your RcvWindow limits you to: 348.48 kbps (43.56 KBytes/s) @ 200ms
Your RcvWindow limits you to: 139.392 kbps (17.424 KBytes/s) @ 500ms
Consider increasing your RWIN value to optimize TCP/IP for broadband.

MTU Discovery (RFC1191) = ON

Time to live left = 112 hops
TTL value is ok.

Timestamps (RFC1323) = OFF

Selective Acknowledgements (RFC2018) = ON

IP type of service field (RFC1349)= 00000000
---------------------------------------------------------------------------------
Hallway Client:
TCP options string = 020405ac01010402

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) = 8712
RWIN Scaling (RFC1323) = 0 bits
Unscaled Receive Window = 8712
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)
255552 (MSS x 44 * scale factor of 4)
127776 (MSS x 44 * scale factor of 2)
63888 (MSS x 44)

bandwidth * delay product:
Your RcvWindow limits you to: 348.48 kbps (43.56 KBytes/s) @ 200ms
Your RcvWindow limits you to: 139.392 kbps (17.424 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

Lobo · Post by **Lobo** » Thu Jun 28, 2001 1:04 pm

Do the same for clients as you did for host:
Please follow instructions on help page exactly below in signature, take your time and Welcome to Speedguide

pellizzeri · Post by **pellizzeri** » Thu Jun 28, 2001 4:03 pm

Lobo - The differences I see between the host and client settings are RWIN, RWIN Scaling, Unscaled Receive Window and TTL. I used the cablenut adjuster to manually edit mss and mtu and see a place on the adjuster to edit RWIN but don't know if the default TTL field in the adjuster is the same as my TTL value from the analyzer. Neither do I see a place to change the Unscaled Receive window and RWIN scaling values. Do these settings even need to be changed or will adjusting the RWIN also change RWIN Scaling and Unscaled Receive Window values? FYI, I read your Help file but am obviously still a bit confused. -kat

Lobo · Post by **Lobo** » Thu Jun 28, 2001 4:11 pm

Set TTL to 64, that is default, if your RWIN is above 65535 turn on scaling by putting 1 in box that says Tcp1323Opts, put a 0 if below 65535, save to registry at bottom of adjuster and reboot