SuperCharged EVDO - Free Performance Tip

mattengland · Posted: Fri Jun 29, 2007 12:57 pm Post subject:

Some status and current conclusion I'm drawing:

Status: I can get pretty good download speeds now 700-1100 kbps (after home-agent changes, broadband antenna addition, and some RWIN tweaking). My uploads are still terrible (usually 90kpbs or less) compared to others.

Current findings about MTU and RWIN:

There is no consistent answer on what or how RWIN should be (or should be calculated) for my system. It's all over the place, and there seems to be no consistent, authoritative answer.

Further, there seems to be no consistent answer for how to calculate my system's MSS or MTU. Again, all over the place. 'ping -f -l XXX' provides very different answers with unexplained behavior, not to mention that various sources provide different answers.

For now I seem to be getting good download speeds. I'll be seeking help to get my upload speeds higher. I suspect this is a different setting from RWIN (assuming R = "receive"). I also will be looking at http://forums.speedguide.net/ and http://www.broadbandnuts.com/index.php?action=forum forums a little more if I want to have further discussion; I seemed to reach the limit of evdoforums.com's interest in this topic (or I've simply flooded this issue too much and/or worn out my welcome, which would be understandable either way). Prior to that I'll probably be trying to have a discussion with owner of http://www.drtweak.com/ .

I'm also giving Cablenut software another look. When I checked it out on my first utility pass, it seemed to fail rather miserably (I asked it to read registry settings and it came up with nothing, nada zero...so I moved on at that time). Now I see that the folks at the above forums seem to use it a lot, so I'm going to be checking it out.

I'll still be interested in additional suggestions. If you're uncomfortable posting to this thread, feel free to private-message me.

jfulmer · EVDO Heavy User Joined: 30 Jun 2007 Posts: 113

I'm reading this discussion about setting MTUs... and it should be a moot point.

Modern TCP/IP networks enforce the use of PMTU discovery, a description of which can be found at http://www.netheaven.com/pmtu.html.

Essentially, the routers in Sprint's network have PMTU enabled, which block any fragmented packets. If a router would need to fragment a packet, it sends an ICMP message back to the system that sent it, asking it to automatically bump it's MTU down. It continues this until the packet can be sent unfragmented, and the system keeps that setting.

This is the reason why for some people, setting a ping packet with a payload size greater than 996 stops the ping from occurring. Somewhere in the path is an MTU of 1024, and the router in front of that link drops the packet and is sending back an ICMP 'Destination Unreachable' with the 'fragment' bit set. Since we're forcing the packet size, we never get a packet through.

All networks now use PMTU discovery and all desktops and servers have it turned on by default. There are problems with some servers and firewalls which (wrongly) block all ICMP messages.

The upshot is that you shouldn't have to worry about the MTU on your wireless card or network, since it's already properly setting it. If it didn't, you wouldn't be getting any packets through.

mattengland · Posted: Mon Jul 02, 2007 11:25 am Post subject:

jfulmer · EVDO Heavy User Joined: 30 Jun 2007 Posts: 113

Hmmm. I wrote a small book in reply to this, and it appears to have gotten eaten by the anti-spam filter... Smile

I'll summarize tomorrow..

jfulmer · EVDO Heavy User Joined: 30 Jun 2007 Posts: 113

MTU vs RWIN

I'm going to do this very high level, so forgive any slight inaccuracies.

MTU, when talking networking, is just the maximum amount of data in a single packet put on a network. For physical links is strictly arbitrary: ethernet enforces a 1500 MTU, token-ring was 6000, gigabyte ethernet jumbo frames are ~9000... The smaller the MTU, the more packets you can put on a line, which can make multiple protocols/users more responsive (latency). However, you also incur more overhead and reduce your speeds (bandwidth).

RWIN is the TCP windowing size. This is the amount of data that a sender on a network will send before requiring an acknowledgment from the receiver. This is usually the parameter that gets tweaked on 'speed up' software for slower links. A higher RWIN number allows a sender to send more data over a slow link, before requiring an acknowledge packet. If the link, however, drops a lot of packets, a high RWIN can actually slow things down, since it will have to resend all data after the dropped packet is resent.

RWIN and MTU are barely linked together. Ideally, RWIN should be some multiple of the MTU. In reality, it really doesn't matter. With a sufficiently high RWIN, you shouldn't really have to worry about the occasional partial packet because of the MTU setting. And, as I said, most systems automatically set MTU, so you really can't control it anyway, except to make it smaller. Some systems set RWIN dynamically as well.

In general, on a slow, reliable link (<1Mbps), a lower MTU and a higher RWIN is desirable. This makes the link more responsive for multiple users/processes, but introduces a little more overhead for the extra TCP/IP packet headers. The old ISDN settings are probably decent. 576 MTU and 256k RWIN might be good numbers to start with. If you do nothing but download, a higher MTU is probably better. On an unreliable link where you lose a significant number of packets, a smaller RWIN is probably better.

krelvinaz · Posted: Tue Jul 03, 2007 8:11 pm Post subject:

Very clear description.

drtweak · EVDO Newbie Joined: 30 Jun 2007 Posts: 1

OK, where to begin Razz

mattengland contacted me via email about how to properly find your MTU and tweak your connection. First, a little bit about myself. I have been doing this for years and you can find a lot of my suggestions, recommendations and tutorials at my website DrTweak.com, Broadbandnuts.com where I'm an Administrator (the makers of CableNut) and Speedguide.net where I have been posting for many years.

There are some misnomers, myths and truths in this thread about increasing your internet connection speed. The first thing to note is that if you are using Windows Vista don't waste your time attempting to tweak your connection, it can't be done. Vista has a new TCP/IP stack that is completely rewritten from Windows 200 & XP and Microsoft in their infinite wisdom have set it so you cannot change any of your TCP and AFD registry entries (the changes that affect your connection speed). Vista has a self tuning TCP/IP stack (as 2000 & XP do as well), but Vista's is more advanced, in my opinion not good enough...... but that's a whole other story.

On to tweaking your connection for optimum throughput (speed). The program that I use and recommend to tweak your connection is CableNut, it will give you the option of optimizing your connection to it's fullest potential. There is no program or tweak that will increase your speed higher than what your ISP caps your connection at. From what I've read here on the forums EVDO's caps (highest rated speed) are 1.4mbps, that is the maximum speed under optimal conditions you can receive, so I will base my recommended settings on this information. Also, there has been a lot of discussion about the proper MTU (Maximum Transmission Unit) value, this value is determined by EVDO, not you, and it sounds as if 1500 is the proper value. 1500 is the maximum size allowed per the internet standard, so with that in mind I would suggest trying the following settings in CableNut and see if they help, these are based on the best possible speed EVDO offers, 1400/800kbps.

DefaultReceiveWindow = 179200
DefaultSendWindow = 102400
DisableAddressSharing = 1
InitialLargeBufferCount = 200
InitialMediumBufferCount = 480
InitialSmallBufferCount = 640
LargeBufferSize = 819200
MaxFastTransmit = 64000
MediumBufferSize = 150400
PriorityBoost = 0
SmallBufferSize = 12800
TransmitWorker = 32
FastSendDatagramThreshold = 1024
EnableFastRouteLookup = 1
EnablePMTUDiscovery = 1
IgnorePushBitsOnReceive = 0
GlobalMaxTcpWindowSize = 64240
MaxFreeTcbs = 8000
MaxHashTableSize = 16384
MaxNormLookupMemory = 5000000
SackOpts = 1
SynAttackProtect = 1
Tcp1323Opts = 0
TcpLogLevel = 1
TcpMaxDupAcks = 3
TcpMaxHalfOpen = 100
TcpMaxHalfRetried = 80
TcpRecvSegmentSize = 1460
TcpSendSegmentSize = 1460
TcpTimedWaitDelay = 30
TcpUseRFC1122UrgentPointer = 0
TcpWindowSize = 64240
MaxConnectionsPer1_0Server = 20
MaxConnectionsPerServer = 10
DefaultTTL = 128
DisableUserTOSSetting = 0
TcpMaxDataRetransmissions = 6
DefaultTOSValue = 92

I'm sorry it has taken me so long to reply to this thread but I have been very busy. The more I read through it the more I saw how misunderstood people were. Also Matt, the reason CableNut didn't show you any values when you first installed it and selected "retrieve current values" is because there are none, Windows 2000 & XP have no hard coded values by default. You also might want to read the following links to get a better understanding of things, I don't have the time to answer every question or misconception listed here but these links will help clear things up.

CableNut Definitions of Values
The Next Generation TCP/IP Stack - this is mostly about Vista although some things were implemented in XPSP2.
[b]The Windows 2000 TCP/IP White Papers/b] - Pretty much the same for XP with some new implementations after SP2 for XP.

Proper TcpReceiveWindow Formula:

(Maximum Bandwidth x Maximum Anticipated Latency) / 8

Example of a Cable connection with a 1500 download cap with an Anticipated Latency of 100 ms:

(1500 x 100) / 8 = 18750 To make it a multiple of MSS divide by 1460:

18750 / 1460 = 12.84246 Then round up to the nearest even whole number:

14 x 1460 = 20440

This is what is sometimes called the base TcpReceiveWindow value. From here it can be increased to take advantage of Windows Scaling if the value is 65535 or greater.

18980 x 2 = 40880
18980 x 3 = 61320
18980 x 4 = 81760 MAX TcpReceiveWindow

*Remember when calculating for your optimum TcpReceiveWindow that latency can possibly rise as high as 300-500ms during a large download and if your TcpReceiveWindow is at least as large as your caps X 500 then no increase in it will produce a faster speed. A HUGE TcpReceiveWindow DOES NOT increase your download speed at all, a value larger than defaults is usually better but there is a point at which you will not increase your speed with increasing this value.

That should be enough information to read for a while, enjoy.

Very Happy

bculp · EVDO Newbie Joined: 04 Jul 2007 Posts: 1

I have a u720 usb sprint card. I bought it for use with my OSX laptop but I installed it on my vista laptop as well.

The vista laptop is a way faster machine than my little powerbook G3.

I consistently get 600-700Kbps upload speeds on various internet bandwidth tests when the u720 is in my powerbook.

When I put it in vista, I can never get more than 200Kbps.

Any clues as to what might cause this?

jfulmer · EVDO Heavy User Joined: 30 Jun 2007 Posts: 113

CrunchDude · Posted: Sat Jul 28, 2007 4:21 am Post subject:

I just tried the tool on my XP partition. It is set to 65534 as opposed to 65536. Is that much of a difference?

I noticed the thread was started 2 years ago, so I don't know if it's still relevant. Another problem I have with it that, from the drop-down menu, I cannot select my Pantech PX-500. I also noticed that ALL other network connections are set to the SAME, including the 65534 setting!? What am I missing here? Thanks guys... Smile

jackrodgers · EVDO Addict Joined: 23 Mar 2006 Posts: 1127

Question: why are all of these tweaks necessary when using a broadband modem card? Shouldn't the card be designed to contain all of its settings and be an autonomous being free of any user changes?

I don't see any reason for a computer to do anything more than receive from a port as fast as possible or send to a port as fast as possible with the card negotiating the data flow.

I can understand an ancient modem needing to negotiate with dozens of different archaic protocals over dialup networks since none had acheived dominance, remember those lists on the box that detailed hundreds of different protocols.

But with a wireless broadband modem that only connects to one telco, I would assume they should be in complete control and as was mentioned above handle certain things automatically.

So, like the kid in that old story that notices the king is naked, I ask why the cards aren't acting autonomously with the user having no choices to make. These decisions should be made by the telco and the computer manufacturer. Apple delivered a plug and play WWAN update and I would think that the Apple engineers working with the Sprint engineers and the card engineers would produce a better result than I ever will making random changes in settings.

The user should be able to insert the card and get the best results possible without worrying about it.

Bigdave · EVDO Addict Joined: 08 Nov 2006 Posts: 1068

Shoulda coulda woulda. . . . . . jack has a point but here's the facts. Most everyone who has tried the tips in this thread, myself included, have seen improvements in their speeds. That being the case then, as a certain non Michael Vick endorsement loving shoe company says . . . . . Just Do It!!! Or don't and keep the speeds you're getting. It is what it is.

An "autonomous being"? Geez. . . . . . Rolling Eyes

ciaobox · EVDO Newbie Joined: 08 Aug 2007 Posts: 9

Hi Dr Tweak,

Regarding your optimization settings that you posted - are they still valid for the Rev-A with the fastest cards? I have a new EX720 and want to be sure I am getting the max (like everyone else, of course!)

dacableguy823 · EVDO Newbie Joined: 12 Aug 2007 Posts: 5

dacableguy823 · EVDO Newbie Joined: 12 Aug 2007 Posts: 5

just got my sprint card running faster then when i got it went from 600 kbps
to almost 1450 kbps and 499 up thats awsome