Changing MTU?

Marcin541

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Changing MTU?

« on: December 04, 2004, 07:07:38 PM »

Would it be a good idea to change my MTU? I currently have 1492 and if i use the Dr TCP thing i guess i can change it to 1500. Is that possible? Is that a good idea? I am on pppoe dsl (1500/384).


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Mr. Hahn

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Changing MTU?

« Reply #1 on: December 05, 2004, 01:29:47 AM »

Yeah, changing your MTU to 1500 is recommended for almost all broadband connections. Go for it. Cool


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VanBuren

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Changing MTU?

« Reply #2 on: December 05, 2004, 02:51:19 AM »

you cant change it, it set by your ISP service.

aslong as you have path MTU detection on you are fine.

its enabled by defult in windows XP

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Mr. Hahn

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Changing MTU?

« Reply #3 on: December 05, 2004, 04:14:24 AM »

You can't change it? I've seen many programs that allow you to. If it isn't changing it, what is it doing to it?


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VanBuren

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Changing MTU?

« Reply #4 on: December 05, 2004, 05:47:35 AM »

Quote from: Mr. Hahn

You can't change it? I've seen many programs that allow you to. If it isn't changing it, what is it doing to it?

If your ISP has set MTU to 1492 there is no way you can overide it to 1500

you can change it lower eg 576, but who wants that, that only give a lower speed.

Path MTU detection works fine, so there is no reason to mess with these settings.

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fred

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Re: Changing MTU?

« Reply #5 on: December 29, 2004, 09:59:45 AM »

I have a program that is called a Rwin calculator it is made by Big Amp if some body will help me to post the file anyone is welcome to it maybe I can do a screen shot of it and somebody may recognize it this program has mtu mss and rwin Very Happy


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VanBuren

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Re: Changing MTU?

« Reply #6 on: December 29, 2004, 11:56:39 AM »

Quote from: fred on December 29, 2004, 09:59:45 AM

Cool, just zip it and click Additional Options... when you write your post, that allow you to Attach files to your post.

Alot of tweak programs has those features too, DR.Tcp has MTU, TCP optimizer has also MTU, Cablenut has MSS thats MTU-40.

My experiance is that there is no need to use those features if you have MTU detection enabled, its enabled by default in most OS.

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fred

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Re: Changing MTU?

« Reply #7 on: December 29, 2004, 05:38:25 PM »

Happy

Holidays van the man that is very correct however if your isp has turned off the icmp ping options in their net work how can you effectively calculate latency for max rwin values in other words that is exactly what my isp has done to me as to not recieve the denial of service attacks that our network has been plaqued with in recent months or they could be just pumping smoke up my ass also I know if you change mtu in the tcp optimizer program it will ask you to return to a mtu of 1500 but I can only set the amount of data to be sent at 995 bits of data or it will start to defrag at any amount higher, strange could you educate me on latency and Rwin or Question

explain 1492 mtu for PPPoe which is set by the isp or 576 for dial up I really do'nt know or understand some of these formulas and they have kind of all melted together after 2 years of trying to get top performance out of this &{;" thing


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VanBuren

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Re: Changing MTU?

« Reply #8 on: December 29, 2004, 06:16:17 PM »

Quote from: fred on December 29, 2004, 05:38:25 PM

Happy

I suggest you use a ping value between 200 and 300 and see what works best for you, try 200 and raise the value to 230 and see if it goes any faster.

As you probl understand its hard to find a good latency value to use by downloading several files until your out of bandwidth, but there is no other way to go beside just testing values. My experiance is that a value between 200 and 300 is optimal.

I never heard of a ISP service before that defrag packets bigger then 995 byte, try cleaning up your registry, in TCP optimizer where you see MTU, delete the value you got there so the field is blank and click save. Also in cablenut program, click delete cablenut tweaks and click save to registry and reboot.

Now all settings should be as windows default.

run this analyzer and post result URL here so i can see it

http://www.dslreports.com/tweaks

here is some info regarding MTU http://www.dslreports.com/faq/7801

and here is some info befind calculating RWIN http://www.dslreports.com/faq/2024

quote "RWIN is determined mathematically. The required variables for the equation are Maximum Potential Speed (MPS) of the line, Maximum Segment Size (MSS) of the packet and Return Trip Time (RTT)(which most people measure with "ping" tests). Depending on the type of connection, a multiplier is usually applied to RTT to account for bad ping days. But generally the simple construction of the equation would be (MPS * Average Worst RTT)/8. The result is then converted to the nearest multiple of MSS."

Edit: here is a example http://www.dslreports.com/faq/6181

quote"Example: MSS is 1460, RTTavg is 125ms, and advertised download speed is 1500Kbps.
125 x 1.5 = 187.5
187.5 x 1500Kbps = 281250
281250 divide by 8 = 35156
35156 divide by 1460 (MSS) = 24.07
Round up to next even number = 26
26 x 1460 = 37960 (Optimal RWIN)."

hope this helps and happy holidays Fred

VanBuren


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fred

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Re: Changing MTU?

« Reply #9 on: December 29, 2004, 07:14:31 PM »

thank you van it will take a while to digest all of this info but I am willing to apply all of this info so as not to be left in the dark like i said after 2 years of trying to come up with the best rwin for my paticular computer it is worth the invested time Very Happy


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fred

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Re: Changing MTU?

« Reply #10 on: December 29, 2004, 09:33:44 PM »

there sure is a lot of strange stuff going on but I will prevail I have'nt been this challenged in a long time thanks again Van theMan
::::::::::.. Download Stats ..::::::::::
Connection is:: 2015 Kbps about 2 Mbps (tested with 1013 KB)
Download Speed is:: 246 kB/s
Tested From:: http://www.testmy.net/
Bottom Line:: 36 times faster than 56K you can download 1MB in 4.16 second(s)
Validation Link:: http://testmy.net/cgi-bin/get.cgi?Test_ID=WOCNP1TXF
could not get the tweak to work server busy I guess will keep o\n trying though I was able to get some ping times from a site that I will not even mention the name HaHa ;)
======================================================================================
=== VisualRoute (R) 2005 Server Edition (v9.0a) report on Dec 29, 2004 11:10:23 PM ===
======================================================================================

Report for www.testmy.net [67.19.36.6]

Analysis: 'www.testmy.net' [6.67-19-36.reverse.theplanet.com] was found in 12 hops (TTL=54). It is running
a HTTP server on port 80 (Apache/1.3.33 (Unix) mod_auth_passthrough/1.8 mod_log_bytes/1.2
mod_bwlimited/1.4 PHP/4.3.10 FrontPage/5.0.2.2635 mod_ssl/2.8.22 OpenSSL/0.9.7a).

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| Hop | %Loss | IP Address | Node Name | Location | Tzone | ms | Graph | Network |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| 0 | | 161.58.180.113 | WIN10115.visualware.com | * | | | | Verio, Inc. VRIO-161-058 |
| 1 | | 161.58.176.129 | - | ?Englewood, CO | | 0 | x | Verio, Inc. VRIO-161-058 |
| 2 | | 161.58.156.140 | - | ?Englewood, CO | | 0 | x | Verio, Inc. VRIO-161-058 |
| 3 | | 129.250.28.206 | xe-1-2-0-3.r20.asbnva01.us.bb.verio.net | Ashburn, VA, USA | -05:00 | 0 | x | Verio, Inc. VRIO-129-250 |
| 4 | | 129.250.5.34 | p16-0-1-1.r21.dllstx09.us.bb.verio.net | Dallas, TX, USA | | 31 | x- | Verio, Inc. VRIO-129-250 |
| 5 | | 129.250.28.167 | ge-1-0-0.a00.dllstx09.us.ra.verio.net | Dallas, TX, USA | | 31 | x- | Verio, Inc. VRIO-129-250 |
| 6 | | 129.250.28.186 | ge-1-2.a00.dllstx04.us.ra.verio.net | Dallas, TX, USA | | 31 | x | Verio, Inc. VRIO-129-250 |
| 7 | | 157.238.228.38 | ge-9-3.a00.dllstx04.us.ce.verio.net | Dallas, TX, USA | | 31 | x- | Verio, Inc. VRIO-157-238 |
| 8 | | 70.85.127.30 | dist-vlan31.dsr3-2.dllstx3.theplanet.com | ?Dallas, TX, USA | | 36 | -x--- | ThePlanet.com Internet Services, Inc. NETBLK-THEPLANET-BLK-13 |
| 9 | | 70.85.127.76 | dist-vlan22.dsr1-2.dllstx2.theplanet.com | ?Dallas, TX, USA | | 31 | x | ThePlanet.com Internet Services, Inc. NETBLK-THEPLANET-BLK-13 |
| 10 | | 12.96.160.8 | dsr2-2-v1.dllstx4.theplanet.com | ?Dallas, TX, USA | | 31 | x | THEPLANET.COM INTERNET SERVICES THEPLANE725-160 |
| 11 | | 67.18.116.70 | gig1-0-1.tp-car9-2.dllstx4.theplanet.com | ?Dallas, TX, USA | | 36 | -x--- | ThePlanet.com Internet Services, Inc. NETBLK-THEPLANET-BLK-11 |
| 12 | | 67.19.36.6 | www.testmy.net | ?Dallas, TX, USA | | 31 | x- | ThePlanet.com Internet Services, Inc. NETBLK-THEPLANET-BLK-11 |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------


« Last Edit: December 29, 2004, 10:14:36 PM by fred »	Logged

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fred

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Re: Changing MTU?

« Reply #11 on: December 29, 2004, 11:02:57 PM »

WEB100 Kernel Variables:
Client: localhost/127.0.0.1
AckPktsIn: 249
AckPktsOut: 0
BytesRetrans: 19320
CongAvoid: 142
CongestionOverCount: 0
CongestionSignals: 12
CountRTT: 168
CurCwnd: 5520
CurMSS: 1380
CurRTO: 360
CurRwinRcvd: 26280
CurRwinSent: 5840
CurSsthresh: 4140
DSACKDups: 0
DataBytesIn: 0
DataBytesOut: 589260
DataPktsIn: 0
DataPktsOut: 427
DupAcksIn: 67
ECNEnabled: 0
FastRetran: 11
MaxCwnd: 16560
MaxMSS: 1380
MaxRTO: 510
MaxRTT: 280
MaxRwinRcvd: 26280
MaxRwinSent: 5840
MaxSsthresh: 8280
MinMSS: 1380
MinRTO: 280
MinRTT: 80
MinRwinRcvd: 26280
MinRwinSent: 5840
NagleEnabled: 1
OtherReductions: 0
PktsIn: 249
PktsOut: 427
PktsRetrans: 14
X_Rcvbuf: 107520
RcvWinScale: 7
SACKEnabled: 3
SACKsRcvd: 78
SendStall: 0
SlowStart: 19
SampleRTT: 170
SmoothedRTT: 130
X_Sndbuf: 107520
SndWinScale: 0
SndLimTimeRwin: 0
SndLimTimeCwnd: 10321546
SndLimTimeSender: 2566
SndLimTransRwin: 0
SndLimTransCwnd: 1
SndLimTransSender: 1
SndLimBytesRwin: 0
SndLimBytesCwnd: 589260
SndLimBytesSender: 0
SubsequentTimeouts: 0
SumRTT: 19420
Timeouts: 1
TimestampsEnabled: 0
WinScaleRcvd: 0
WinScaleSent: 7
DupAcksOut: 0
StartTimeUsec: 681475
Duration: 10324505
c2sData: 2
c2sAck: 2
s2cData: 9
s2cAck: 2
half_duplex: 0
link: 100
congestion: 1
bad_cable: 0
mismatch: 0
spd: 0.00
bw: 0.54
loss: 0.028103044
avgrtt: 115.60
waitsec: 0.36
timesec: 10.00
order: 0.2691
rwintime: 0.0000
sendtime: 0.0002
cwndtime: 0.9998
rwin: 0.2005
swin: 0.8203
cwin: 0.1263
rttsec: 0.115595
Sndbuf: 107520

Checking for mismatch condition
   (cwndtime > .3) [0.99>.3], (MaxSsthresh > 0) [8280>0],
    (PktsRetrans/sec > 2) [1.4>2], (estimate > 2) [0.54>2]
Checking for mismatch on uplink
   (speed > 50 [0>50], (xmitspeed < 5) [0.29<5]
   (rwintime > .9) [0>.9], (loss < .01) [0.02<.01]
Checking for excessive errors condition
   (loss/sec > .15) [0.00>.15], (cwndtime > .6) [0.99>.6],
   (loss < .01) [0.02<.01], (MaxSsthresh > 0) [8280>0]
Checking for 10 Mbps link
   (speed < 9.5) [0<9.5], (speed > 3.0) [0>3.0]
   (xmitspeed < 9.5) [0.29<9.5] (loss < .01) [0.02<.01], (mylink > 0) [3.0>0]
Checking for Wireless link
   (sendtime = 0) [2.0E=0], (speed < 5) [0<5]
   (Estimate > 50 [0.54>50], (Rwintime > 90) [0>.90]
    (RwinTrans/CwndTrans = 1) [0/1=1], (mylink > 0) [3.0>0]
Checking for DSL/Cable Modem link
   (speed < 2) [0<2], (SndLimTransSender = 0) [1=0]
    (SendTime = 0) [2.0E-4=0], (mylink > 0) [3.0>0]
Checking for half-duplex condition
   (rwintime > .95) [0>.95], (RwinTrans/sec > 30) [0>30],
    (SenderTrans/sec > 30) [0.1>30], OR (mylink <= 10) [3.0<=10]
Checking for congestion
   (cwndtime > .02) [0.99>.02], (mismatch = 0) [0=0]
   (MaxSsthresh > 0) [8280>0]

estimate = 0.54 based on packet size = 10Kbits, RTT = 115.6msec, and loss = 0.028103044
The theoretical network limit is 0.54 Mbps
The NDT server has a 105.0 KByte buffer which limits the throughput to 7.09 Mbps
Your PC/Workstation has a 25.0 KByte buffer which limits the throughput to 1.73 Mbps
The network based flow control limits the throughput to 1.09 Mbps

Client Data reports link is 'T1', Client Acks report link is 'T1'
Server Data reports link is '10 Gig', Server Acks report link is 'T1
all of this info is froma web site I will put the link into upon CA3LE GUY's approval it is so strange I get the same results every time now that I have followed your instructions Van the Man


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VanBuren

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Re: Changing MTU?

« Reply #12 on: December 30, 2004, 05:01:53 AM »

Delete all tweaks like i said in my previous post, then run a new TCP dump from Web 100

it says your MSS is 1380 and that give you a MTU of 1420

lets see if you get more then that after deleting all the tweaks.

When we know the MSS without tweaks i can make a custom cablenut file for you, just tell me what cap you have

VanBuren


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fred

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Re: Changing MTU?

« Reply #13 on: December 30, 2004, 07:19:14 AM »

Good morning Van my my caps are1200kdwn and256kup I could'nt get any connectivety when I wiped the slate clean so I went back and put
mtu@1500
ttl@64
rwin65535
mtu discovery@yea
seletiveaks@yes
max dupak's@3
trun off rfc 1323
this is what I got
WEB100 Kernel Variables:
Client: localhost/127.0.0.1
AckPktsIn: 232
AckPktsOut: 0
BytesRetrans: 21900
CongAvoid: 129
CongestionOverCount: 0
CongestionSignals: 11
CountRTT: 151
CurCwnd: 4380
CurMSS: 1460
CurRTO: 360
CurRwinRcvd: 65535
CurRwinSent: 5840
CurSsthresh: 2920
DSACKDups: 0
DataBytesIn: 0
DataBytesOut: 575240
DataPktsIn: 0
DataPktsOut: 394
DupAcksIn: 68
ECNEnabled: 0
FastRetran: 11
MaxCwnd: 13140
MaxMSS: 1460
MaxRTO: 720
MaxRTT: 270
MaxRwinRcvd: 65535
MaxRwinSent: 5840
MaxSsthresh: 5840
MinMSS: 1460
MinRTO: 330
MinRTT: 80
MinRwinRcvd: 62615
MinRwinSent: 5840
NagleEnabled: 1
OtherReductions: 0
PktsIn: 232
PktsOut: 394
PktsRetrans: 15
X_Rcvbuf: 65535
RcvWinScale: 2147483647
SACKEnabled: 3
SACKsRcvd: 73
SendStall: 0
SlowStart: 18
SampleRTT: 170
SmoothedRTT: 130
X_Sndbuf: 65535
SndWinScale: 2147483647
SndLimTimeRwin: 0
SndLimTimeCwnd: 10266210
SndLimTimeSender: 11389
SndLimTransRwin: 0
SndLimTransCwnd: 1
SndLimTransSender: 1
SndLimBytesRwin: 0
SndLimBytesCwnd: 575240
SndLimBytesSender: 0
SubsequentTimeouts: 0
SumRTT: 18100
Timeouts: 0
TimestampsEnabled: 0
WinScaleRcvd: 2147483647
WinScaleSent: 2147483647
DupAcksOut: 0
StartTimeUsec: 260101
Duration: 10303712
c2sData: 2
c2sAck: 2
s2cData: 2
s2cAck: 2
half_duplex: 0
link: 100
congestion: 1
bad_cable: 0
mismatch: 0
spd: 0.00
bw: 0.56
loss: 0.027918782
avgrtt: 119.87
waitsec: 0.00
timesec: 10.00
order: 0.2931
rwintime: 0.0000
sendtime: 0.0011
cwndtime: 0.9989
rwin: 0.5000
swin: 0.5000
cwin: 0.1003
rttsec: 0.119868
Sndbuf: 65535

Checking for mismatch condition
   (cwndtime > .3) [0.99>.3], (MaxSsthresh > 0) [5840>0],
    (PktsRetrans/sec > 2) [1.5>2], (estimate > 2) [0.56>2]
Checking for mismatch on uplink
   (speed > 50 [0>50], (xmitspeed < 5) [0.30<5]
   (rwintime > .9) [0>.9], (loss < .01) [0.02<.01]
Checking for excessive errors condition
   (loss/sec > .15) [0.00>.15], (cwndtime > .6) [0.99>.6],
   (loss < .01) [0.02<.01], (MaxSsthresh > 0) [5840>0]
Checking for 10 Mbps link
   (speed < 9.5) [0<9.5], (speed > 3.0) [0>3.0]
   (xmitspeed < 9.5) [0.30<9.5] (loss < .01) [0.02<.01], (mylink > 0) [3.0>0]
Checking for Wireless link
   (sendtime = 0) [0.00=0], (speed < 5) [0<5]
   (Estimate > 50 [0.56>50], (Rwintime > 90) [0>.90]
    (RwinTrans/CwndTrans = 1) [0/1=1], (mylink > 0) [3.0>0]
Checking for DSL/Cable Modem link
   (speed < 2) [0<2], (SndLimTransSender = 0) [1=0]
    (SendTime = 0) [0.0011=0], (mylink > 0) [3.0>0]
Checking for half-duplex condition
   (rwintime > .95) [0>.95], (RwinTrans/sec > 30) [0>30],
    (SenderTrans/sec > 30) [0.1>30], OR (mylink <= 10) [3.0<=10]
Checking for congestion
   (cwndtime > .02) [0.99>.02], (mismatch = 0) [0=0]
   (MaxSsthresh > 0) [5840>0]

estimate = 0.56 based on packet size = 11Kbits, RTT = 119.87msec, and loss = 0.027918782
The theoretical network limit is 0.56 Mbps
The NDT server has a 63.0 KByte buffer which limits the throughput to 4.17 Mbps
Your PC/Workstation has a 63.0 KByte buffer which limits the throughput to 4.17 Mbps
The network based flow control limits the throughput to 0.83 Mbps

Client Data reports link is 'T1', Client Acks report link is 'T1'
Server Data reports link is 'T1', Server Acks report link is 'T1'


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Re: Changing MTU?

« Reply #14 on: December 30, 2004, 07:34:12 AM »

hey again Fred, MTU is back on track now Very Happy

try this file, it should give you a more optimal RWIN

just open adjuster and click load custom settings file, dont forget to click save to registry

good luck

VanBuren


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