Author Topic: MTU settings (over 20 hops distance)  (Read 589 times)

Offline Saintaw

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MTU settings (over 20 hops distance)
« on: April 14, 2000, 01:19:00 AM »
I previously had my MTU settings set at 1500 (am on a 56K/V90 Mobem with a BT cr***p line that gives me 3120 kb/s max). and had quite some stable fights...

I now set it back to 567 to test it and suffered a lot more warps than before...I will leave it this way for a couple of days to be sure, but...


Go figure...


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[This message has been edited by Saintaw (edited 04-14-2000).]
Saw
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Offline Badger

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MTU settings (over 20 hops distance)
« Reply #1 on: April 14, 2000, 06:36:00 AM »
Saw....

I'm using @Home service on a cable modem.  I used to fret about these settings daily and everytime I would read the latest urban legend about what they should be set to, or someone would recommend a new program for this, I'd run off and make changes.  Pretty soon, I think my registry was so polluted, I'm not sure anything was working. I did a lot of reading and finally set mine to 32,767 which I realize is huge, but after that my download speeds on cable modem jumped significantly.  I changed nothing else from the virgin delivery state of WIN98SE.  Since I don't just play AH, I needed something that would handle my every day business needs etc.  I get 50-60ms response to HTC from Toronto on many off peak hours and maybe it jumps to 150-250 during heavy Internet prime time.  I used to have virtually NO warping of other planes, but since v1.02 came out, I have noticed a significant amount of that, especially in close to them.  Perhaps that's a direct result of more users in the arena and a function/factor of server loadings.

Regards,
Badger

Offline Badger

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MTU settings (over 20 hops distance)
« Reply #2 on: April 14, 2000, 06:42:00 AM »
Q: How do I get the maximum possible DSL or cable modem speed under Windows 95/98/NT/2000? Should I use one of those tweaking programs?

A: The only Windows 95/98/NT/2000 network setting that has any real effect on DSL or cable modem speed is the TCP receive window size, DefaultRcvWindow for Windows 95/98, or TcpWindowSize for Windows NT/2000. Everything else commonly recommended (e.g., TTL) are urban myths that won't help. To modify your TCP receive window size, use one of the following two methods:

Method 1

Save the appropriate four (4) lines of text below to your Desktop in the file name indicated (or just click the accompanying link while holding down the Shift key to download the file), and then double-click on the resulting file to add the setting into your Registry. However, this does not clean out any dial-up modem "tweaks" that might interfere with cable modem/DSL speed -- if you need to do that, use

Method 2 (preferred).

Normal Latency*
(e.g., normal DSL or 2-way cable)
32K Window Windows 95/98
TCPRW32K.REG REGEDIT4
[HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP]
"DefaultRcvWindow"="32767"
 
Windows NT/2000
NTTCP32K.REG REGEDIT4
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
"TcpWindowSize"=dword:00007fff
 
High latency*
(e.g., poor DSL or 1-way cable)
64K Window Windows 95/98
TCPRW64K.REG REGEDIT4
[HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP]
"DefaultRcvWindow"="65535"
 
Windows NT/2000
NTTCP64K.REG REGEDIT4
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
"TcpWindowSize"=dword:0000ffff
 

* Latency: Check latency with 'ping' (or 'traceroute') to a number of distant hosts. (See Important Note below under "Latency") Reasonable rough rules of thumb are that low latency is below 100 ms, and high latency is above 200 ms (with normal latency in the middle).


From a great site that you may want to check and read:

 http://navasgrp.home.att.net/tech/cable_dsl.htm

Offline Skuzzy

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MTU settings (over 20 hops distance)
« Reply #3 on: April 14, 2000, 08:57:00 AM »
Well, could not help myself, I have to put in my $0.02 worth.  Badger, you are correct, but I think a bit more explanation is in order.

The window size, which Badger is talking about, can have an impact on performance, but there are several scenarios which can make it have an impact on performance.

First, understand that the "window size" of the TCP stack is used to allow data to come into (in the case of the receive window) your computer and be buffered in that window until your computer can process it.

Knowing that, it starts becoming clear, the performance of your connection as well as the speed of your computer is what determines how much of that window and how large that window needs to be.

As an extreme example, take a 200 Mhz PC with a very fast connection to the Internet, say a T1 (1.45Mb/s).  The sliding window should be enlarged as data, especially for games, will not be able to get processed by the CPU fast enough, so a larger window will allow data to continue to come in while the CPU is busy messing with the current packet of data.
The converse of that is a very fast CPU (>500Mhz) with a 56K modem connection.  The sliding window will have virtually no effect on the performance as the data will get processed faster than the computer could receive it.

So the sliding window can have a very high impact on performance, or none at all.  If your computer is fast enough to process the data coming into it, then the sliding window will not have a chance to be used.

Keeping in mind, for games in particular, the CPU must not only digest the data, but take the appropriate action on that data, which means getting it displayed on the monitor, before acting on the next packet.  So a slow video card can cause data to get backed up in the TCP rcv window.

Also, the amount of data for any given action has to be considered.  General surfing requires enormous amounts of data to be passed between you and the Internet and the TCP rcv window will usually be used, no matter what type of connection your have.

In Aces High, and to HTC's credit, the game requires very little Internet data to run properly.  So the sliding window size should have little or no effect on this sim, but for general surfing it has the potential to be very dramatic.

Oh, and the MTU size will make an impact on the performance of most Internet games.  Notice I said most.  I have tested 30 some odd Internet games for bandwidth utilization (i.e the amount of data they need for any given connection) and this sim is the most efficient game I have ever seen.

So, it is possible to optimize your computer for either general surfing, or gaming, or find a compromise between the two, but they both have very different data requirements, and place very different loads on your computer system.



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Offline Badger

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MTU settings (over 20 hops distance)
« Reply #4 on: April 14, 2000, 09:08:00 AM »
Skuzzy....

Slightly off this topic, but I just wanted to say that it's fabulous to have such a knowlegeable and contributing resource such as yourself available to answer network and communciations questions for AH users.

It is obvious you know your subject well and I bet over time it will help a great many users solve one of the most frustration problems of on-line gaming, being latency and connection quality.

On behalf of all of us.....

Thank you...<salute>

Regards,
Badger

Offline Skuzzy

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MTU settings (over 20 hops distance)
« Reply #5 on: April 14, 2000, 09:16:00 AM »
 
Quote
Originally posted by Badger:
Saw....

I'm using @Home service on a cable modem.  I used to fret about these settings daily and everytime I would read the latest urban legend about what they should be set to, or someone would recommend a new program for this, I'd run off and make changes.  Pretty soon, I think my registry was so polluted, I'm not sure anything was working. I did a lot of reading and finally set mine to 32,767 which I realize is huge, but after that my download speeds on cable modem jumped significantly.  I changed nothing else from the virgin delivery state of WIN98SE.  Since I don't just play AH, I needed something that would handle my every day business needs etc.  

FYI badger, when you set the MTU to larger than 1500, which I am not surprised MS allows, you end up sending or asking for packets of data which requires the packets to be fragmented, as routers on the Internet will not transport a data packet over 1524 bytes in size.
This also requires your computer to wait for those fragmented packets, before it can assemble them into the large packet you wanted.
If you stay on the @home network, you are probably okay, as the @home network caches WEB sites and FTP data on local network servers (whether you use thier proxy or not).

The @home and road runner networks are built like AOL's network, where they have peering into the Internet backbones at various locations, and make every attempt to keep you on thier network.  It is a resonably good model for the type of service they are offering.

Setting the MTU past 1500 for general Internet connections to regular ISP's will cause problems.  If any part of a fragmented packet gets lost, it requires the whole packet to be retransmitted again.  This is corrected in IPV6, but IPV4 (the current IP standard) does not deal with lost packet fragments very well.

Cable modem services are very different than regualr Internet connections, just like AOL's connections are also very different and all these somewhat private networks have very different requirements than a general purpose Internet connection via a regular ISP.

Just thought I would clarify this a bit.




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Offline Wanker

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MTU settings (over 20 hops distance)
« Reply #6 on: April 14, 2000, 09:20:00 AM »
Wow, thanks for the info, Skuzzy. What would you recommend for settings for my Win98FE system with an @HOME cable modem, if I want to optimize my system for downloading files.

I'm running an Intel PIII-550E slot one overclocked to 733Mhz, 256MB PC100 RAM with a Guillemot Prophet DDR-DVI GeForce video card.

Thank you!

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banana
308 (Polish) Squadron "City of Cracow" RAF

[This message has been edited by banana (edited 04-14-2000).]

Offline Skuzzy

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MTU settings (over 20 hops distance)
« Reply #7 on: April 14, 2000, 12:34:00 PM »
 
Quote
Originally posted by banana:
Wow, thanks for the info, Skuzzy. What would you recommend for settings for my Win98FE system with an @HOME cable modem, if I want to optimize my system for downloading files.

I'm running an Intel PIII-550E slot one overclocked to 733Mhz, 256MB PC100 RAM with a Guillemot Prophet DDR-DVI GeForce video card.

Thank you!



banana, with that system, I dont think there is much more you can do to help performance.  You should go ahead and set the MTU to 576 though.

As for the rcv window.  Badger posted a link to the @home site that talks about TCP mods, and while I have not read it, they may be targeting the general surfer, so keep that in mind.

It wont hurt to set the MTU to 576, and if you see no difference, change it back to 1500.


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Offline Skuzzy

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MTU settings (over 20 hops distance)
« Reply #8 on: April 14, 2000, 12:49:00 PM »
 
Quote
Originally posted by Badger:
Skuzzy....

Slightly off this topic, but I just wanted to say that it's fabulous to have such a knowlegeable and contributing resource such as yourself available to answer network and communciations questions for AH users.

It is obvious you know your subject well and I bet over time it will help a great many users solve one of the most frustration problems of on-line gaming, being latency and connection quality.

On behalf of all of us.....

Thank you...<salute>

Regards,
Badger

<BLUSH>  Gee, thanks badger.

Been doing this type of work for the better part of 20 years (anyone else heard of DARPA NET?).

One of the many things I have learned, there is no one answer to solving connections issues, but armed with quality information, a consumer will invariably make a decent decision.

My goal is to help people understand how it all works.  It all goes to helping reduce frustration with connections.  

Its like flying here.  When I first entered the TA, I got so frustrated.  I could not understand why folks could get behind me so easily and why I could not shake em, or get behind someone else.
A few pilots (thank you hitech, weazel, indian, sharky, and dukem) passed on what they know and now, I am having a ball.
Just understanding why anything works and being able to sit back and say, "Oh, I know why that happened" is pretty gratifying.

I like to think that is true of most things in life.

No thank are required or expected.  If anything I pass along will help anyone, then that is good enough for me.



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Roy "Skuzzy" Neese
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funked

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MTU settings (over 20 hops distance)
« Reply #9 on: April 14, 2000, 04:11:00 PM »
Skuzzy, I am on a LAN at a university.  I don't know what I'm connected to beyond the LAN, but my pings to HTC are about 50ms from Illinois.  Do you have any suggestions on settings I might play around with?

Offline Camel

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MTU settings (over 20 hops distance)
« Reply #10 on: April 14, 2000, 04:50:00 PM »
I vote Skuzzy gets his own foru0m  

Thanks Bud!

Offline Skuzzy

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MTU settings (over 20 hops distance)
« Reply #11 on: April 14, 2000, 05:03:00 PM »
 
Quote
Originally posted by funked:
Skuzzy, I am on a LAN at a university.  I don't know what I'm connected to beyond the LAN, but my pings to HTC are about 50ms from Illinois.  Do you have any suggestions on settings I might play around with?

Yes, I have avoided LAN's with high speed connections to the Internet in all this talk.  If you are getting a 50ms ping time, and getting it pretty consistently, I would just smile.

I think most of the guys here are turning a fair shade of green about right now funked  .

The whole key to all this tuning starts by asking a question.  "Is the data flow pretty smooth?"  If the answer is yes, then leave it alone, if it is not then some tweaking may be in order.
Now, if you have a high speed connection tto the Internet, over a LAN especially, you may really never get the data to flow very smoothly.  On a setup like this you are very exposed to the eddys and currents of the Internet data stream.

I have the same benefit here, being on a LAN, but I have the advantage of being on the same LAN as the HTC server.  So my game play is always pretty smooth.  Now, I see as much warping of other planes as the next guy.  Has nothing to do with my connect, it is the other player that is warping and his/her connect is showing signs of slow data spurts.

Bottom line funked:  I would not touch a thing in your case.



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Offline Skuzzy

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MTU settings (over 20 hops distance)
« Reply #12 on: April 14, 2000, 05:05:00 PM »
 
Quote
Originally posted by Camel:
I vote Skuzzy gets his own foru0m  

Thanks Bud!

No problem.  My own forum???  I dunno about that.  But most of what I talk about should probably be moved from the general discussion and into the technical group.

I need to keep that in mind as we all do.




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Offline daddog

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MTU settings (over 20 hops distance)
« Reply #13 on: April 14, 2000, 05:17:00 PM »
So, what squad you in?

Are you a cat or dog lover?  

Just wondering...

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Offline Skuzzy

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MTU settings (over 20 hops distance)
« Reply #14 on: April 14, 2000, 05:45:00 PM »
 
Quote
Originally posted by daddog:
So, what squad you in?

Are you a cat or dog lover?  

Just wondering...


As far as animals go , I like both.  I am not in a squad, as I am in the "barely knows where the altimeter is" mode.

Still training.  Hope to get into the MA sometime in the near future,.....I hope  .

Wish I knew as much about flying as I do about networks.



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Roy "Skuzzy" Neese
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