MTU stuck at 1460? Can you check yours for me?

Thar · May 02, 2006, 22:07:06

Since being upgraded to Max I have attempted to tweak my connection. I changed the RWIN figure successfully but I'm having problems with the MTU.

I worked out using the ping test that the optimum for me is 1478 but despite changing it using DrTCP, it's stuck at 1460.

I've checked the MTU on the router which was 1500 so I changed that to 1478, no change, still reporting at 1460 by Broadband Reports Tweak Tester and Speedguide.net.

I downgraded my router's (Netgear DG834G) firmware and upgraded back but no change.

I've even tried other tweak tools, TCP Optimizer and Cablenut to no avail.

My PC registry shows the MTU as 1478 all the time?

I have finally found another IDNetter who has the same problem and am wondering whether it's something to do with the IDNet side rather than my side.

I know several of you have changed the MTU but did you reperform the Tweak Test and confirm the value has been at your value?

Would appreciate your comments.

Gilba · May 02, 2006, 22:31:21

I have the same router as you. I changed my mtu a while back from 1458 to 1400 and just ran the tweak test, which has just confirmed my change. So I don' think its a problem with IDNet.

Thar · May 02, 2006, 22:44:28

Thanks for replying, strange someone else with a different router has the same problem though?

Gilba · May 02, 2006, 22:54:21

Not to state the obivious but do you restart your comp every time you change the settings in the tweak apps. I only changed the MTU within the router settings and left the Rwin alone.

Thar · May 02, 2006, 23:03:27

Yes, I rebooted after the changes.

I found a good improvement in speed after changing the RWIN personally.

Jeff · May 05, 2006, 21:54:34

RWIN is a good tweak, particularly if you happen to download from far afield geographically

One thing you can try Thar is to open up Registry Editor (Start > Run > regedit > hit enter), hold down CTRL and then type f, type in MTU in box, click find. It will search and find any entries for MTU. To continue with the search, just press F3 from here on in. If you see any entries that aren`t 1478, change them

*Disclaimer - Registry is the heart and soul of everything on your PC, enter at your own risk! For safetys sake, before attempting to manually edit the registry, first click file and then export, which will back it up.*

Thar · May 05, 2006, 22:05:10

Thanks Jeff but I've already confirmed that the registry has the MTU as 1478.

I have 3 machines on my network. I've attempted to change the MTU on 2 of them so far without success. I finally checked my laptop yesterday which had the MTU value set at 1500, so I changed this to 1478. The testers then also came back as 1460 on this even though the registry clearly shows the MTU as 1460???

Been using DrTCP to tweak my settings for 3 years or so and I've never had this problem before.

I'm really at a loss with this.

mrapoc · May 05, 2006, 22:11:45

same happens for mine but it does show as 1478 in reg
100% efficiency transfer according to broadband report

Jeff · May 05, 2006, 22:33:28

Thar, I made a point of posting to someone before about making sure that if you have ever installed software to tweak connection, many of these programs reinstall the config. file on bootup to ensure that the changes you made are universal. Perhaps, if you have such a program(s) installed, maybe undo any changes you`ve ever made and uninstall the program(s)?

mrapoc, nice going man

Thar · May 05, 2006, 22:42:46

Same here from Broadband Reports

1. Your Tweakable Settings:
Receive Window (RWIN): 76680
Window Scaling: 1
Path MTU Discovery: ON
RFC1323 Window Scaling: ON
RFC1323 Time Stamping: OFF
Selective Acks: ON
MSS requested: 1420
TTL: unknown
TTL remaining: 116
TOS/TOS subfield: 0
TOS/Flags:

2. Test 39761 byte download
Actual data bytes sent: 39761
Actual data packets: 29
Max packet sent (MTU): 1460
Max packet recd (MTU): 1460
Retransmitted data packets: 0
sacks you sent: 1
pushed data pkts: 4
data transmit time: 0.703 secs
our max idletime: 3013.8 ms
transfer rate: 10285 bytes/sec
transfer rate: 82 kbits/sec
This is not a speed test!
transfer efficiency: 100%

Jeff - I've only ever used DrTCP until now. I've tried blanking out the settings to go back to default settings but all this does is change the RWIN back to what it was. Since discovering the MTU problem I've tried Cablenut and TCP optimizer but have since undone the changes made in these.

The only thing I haven't tried is a format and reinstall $:-\$ If I get bored I might see if that would cure it.

Jeff · May 05, 2006, 22:58:38

Try this which I have installed and seems to work and doesn`t contain any dodgy config or batch files. Instead of uing optimise, click the right hand slider at the bottom and enter

MTU: 1478

RWIN: 145948

TTL: 64

Session Alive: 300000ms

Check Auto Discover and Selective Acks

NDI Cache: 32

Last option, best left disabled. Clicky apply each time you change, reboot and retest, report back

The long method here: http://support.microsoft.com/default.aspx?scid=kb;en-us;826159

Hey, 1460 is probably not gonna change anything for you one iota I reckon anyway, but I think your RWIN may be a tad small, but should be OK.

http://support.microsoft.com/default.aspx?scid=kb;en-us;826159

Thar · May 05, 2006, 23:28:26

I downloaded the program and used the settings you advised. I rebooted and re-ran Tweak tester and none of the changes had taken, I did click Apply to all before exiting. $:-\$

So I blanked out DrTCP to be sure and re-booted (again) but RWIN now at default of 65535

I realise the MTU value probably isn't a big issue but I'm a Why? person and want to get to the bottom of it

Jeff · May 05, 2006, 23:32:54

65535 is Windows default

I`m a why person too, get ya drift

This is what is throwing me, Windows is already recognising that you`re reverting to default, but not for MTU?? This is why I`m thinking that something 3rd party is gatecrashing!

Well, I`m man enough to admit when I`m stumped!

Any cliffs your way?

Thar · May 06, 2006, 00:06:06

Well you're the 3rd person besides me that I've stumped with this. $:-\$

Just have to stick with RWIN tweaks I think

mrapoc · May 07, 2006, 18:25:49

i have tried 2 tweaks but none seem to have done anything... until i came across tweak tester at www.broadbandreports.com which proves otherwise - 100% transfer efficiency and all seems well

brizo · Jul 04, 2006, 08:53:20

Hi all,

Sorry to bring this thread back up, but I've been searching since migrating in on Friday.

I thought I was going round the bend!!!

I too have this weird problem using a Mac, 10.4.7 and a DG834, and I cannot for the life of me get it resolved. Never had this problem in the past.

Has anyone found a solution?

Thanks.

pmb53 · Jul 04, 2006, 11:34:38

It appears IDNets routers are set to MTU 1460 for some reason. I've set my MTU at 1430, Rwin 111200 which seems to work very well.

brizo · Jul 04, 2006, 12:04:16

Thanks pmb53.

I wonder why the routers are set to 1460?

Anyway, at least I'm saved from the men in white coats!

maxping · Jul 04, 2006, 18:02:28

Quote from: pmb53 on Jul 04, 2006, 11:34:38
It appears IDNets routers are set to MTU 1460 for some reason. I've set my MTU at 1430, Rwin 111200 which seems to work very well.

200220/1500 here.

Najarak · Jul 04, 2006, 22:30:57

Quote from: brizo on Jul 04, 2006, 08:53:20

I too have this weird problem using a Mac, 10.4.7 and a DG834, and I cannot for the life of me get it resolved. Never had this problem in the past.

I use Mac OSX 10.4.7 and a DG834G, although the Mac is connected via ethernet not wirelessly, The router has the MTU set at 1500. The System Prefs Network Ethernet pane is set to let the Mac configure "Automatically", I have tried fiddling with it in the past and found that it seems to work best for me if left on Auto. 8)

pmb53 · Jul 05, 2006, 12:17:00

Quote from: maxping on Jul 04, 2006, 18:02:28
Quote from: pmb53 on Jul 04, 2006, 11:34:38
It appears IDNets routers are set to MTU 1460 for some reason. I've set my MTU at 1430, Rwin 111200 which seems to work very well.

200220/1500 here.

What does this test say your MTU is? http://www.dslreports.com/tweaks

Jeff · Jul 08, 2006, 23:33:26

FEI, BT don`t recommend setting an MTU higher than 1458 in any case.

maxping · Jul 09, 2006, 15:58:23

I emailed Simon as i have DrTsp set to 1500 MTU but the speed test shows 1460.

I also changed it in the Router settings.

He said they do not limit MTU so how do i change it?

Test yours here - - http://www.dslreports.com/tweaks

mrapoc · Jul 09, 2006, 16:51:58

mine is 1430

maxping · Jul 09, 2006, 17:19:30

Are you using DrTcp?

mrapoc · Jul 09, 2006, 18:42:59

im gonna keep it there coz jeff recommends it - tweaking for max dsl
unless there is a better setting
and yes i am using it

Jeff · Jul 14, 2006, 21:20:56

Remember to always reboot equipment and PC after altering any changes, empty out your caches so DSL Reports doesn`t confuse any new tests with earlier ones performed

Tweaking is what the name suggests. It will either slightly increase or decrease your performance. Personally, I think we read too much into tweaking, especially these days with Max. I used to tweak my DUN connection as the difference between a throughput of 4KB/sec and 6 KB/sec could often mean days saved waiting for a download to finish!

If I was to set up 2 identical machines on two identical lines, one with windows default setting and one with tweaked settings, without performing any speedtests, would you be able to tell the difference? Honestly, I wouldn`t ... it`s a bit like the Pentium 4 2.2GHz vs Pentium 4 2.4GHz, only SiSoft and 3D Mark et al will tell you the difference, if you use `em both normally, not even Bill Gates would know the difference

Thar · Sep 08, 2006, 14:02:52

Well bugger me!

Have recently been reading a post on another board where the poster was asking for RWIN advice. I thought I'd check my settings with DSL Reports as I haven't done it for some time.

Guess what...my MTU is now showing as 1478!

Now the only thing I can think of that I have changed since discovering the problem is Zone Alarm. I recently upgraded from 5. something to 6.1.744. I not 100% certain that it's the cause but after updating ZA I noticed my speeds had increased slightly.

My RWIN figure wasn't the same as I have set in DrTCP but I've re-tweaked that and it's now reporting correctly.

If anyone still has this anomalie, try doing a tweak test and see what you get.

Happy now!

Rolacka · Sep 08, 2006, 16:42:27

Mine seems fine.

Receive Window (RWIN):    128480
Window Scaling:    1
Path MTU Discovery:    ON
RFC1323 Window Scaling:    ON
RFC1323 Time Stamping:    OFF
Selective Acks:    ON
MSS requested:    1460
TTL:    unknown
TTL remaining:    53
TOS/TOS subfield:    0
TOS/Flags:

2. Test 1024001 byte download      Actual data bytes sent: 1077101
Actual data packets: 740
Max packet sent (MTU): 1500
Max packet recd (MTU): 1500
Retransmitted data packets: 37
sacks you sent: 147
pushed data pkts: 172
data transmit time: 31.934 secs
our max idletime: 1419.6 ms
transfer rate: 31652 bytes/sec
transfer rate: 253 kbits/sec
This is not a speed test!
transfer efficiency: 95%

equk · Sep 08, 2006, 17:03:39

surely MTU will never be 1500 on ADSL PPPoA as the PPP headers take up a certain number of bytes?

Here's some info I found.

QuoteFor pppoa/vcmux in the UK the optimal MTU is 1478 - the pppoa overhead is
10. (1478+10) / 48 = 31 whole cells, each which get another 5 bytes ATM
header added.

QuoteWindows PPPoE connection supports an IP MTU of 1480 bytes. The 20 bytes of overhead consist of the PPPoE header (6 bytes), the largest possible outer PPP header (4 bytes), the largest possible Multilink PPP header (4 bytes), the largest possible PPP header for compression and encryption (4 bytes), and the PPP header that identifies the actual packet being sent (2 bytes).

QuoteA size of 1492 is the highest MTU a PPPoE DSL connection can attain. This is because of the extra 8 bytes required for Encapsulating the PPP protocol to Ethernet

I notice a few ISPs suggest changing MTU to 1492 on PPPoA so not sure

mrapoc · Sep 08, 2006, 17:08:09

honestly, lol, maybe if it was getting you 10KB/s extra but i doubt it will even get you this...id rather have more stability than a small increase in speed (found this out while tweaking my connection!)

equk · Sep 08, 2006, 17:20:57

I just tried that broadbandreports thing:

QuoteActual data bytes sent: 1077281
Actual data packets: 751
Max packet sent (MTU): 1480
Max packet recd (MTU): 1500
Retransmitted data packets: 37
sacks you sent: 152
pushed data pkts: 104
data transmit time: 33.219 secs
our max idletime: 2821.3 ms
transfer rate: 30245 bytes/sec
transfer rate: 241 kbits/sec
This is not a speed test!
transfer efficiency: 95%

Thar · Sep 08, 2006, 22:05:30

Quote from: mrapoc on Sep 08, 2006, 17:08:09
honestly, lol, maybe if it was getting you 10KB/s extra but i doubt it will even get you this...id rather have more stability than a small increase in speed (found this out while tweaking my connection!)

It's never been about the speed.

I just couldn't understand why my MTU was stuck at 1460 despite using various tweaking tools and it reporting correctly in the registy.

I'm still not sure what it was but at least it's reporting correctly now.

MoHux · Sep 09, 2006, 17:09:31

Thar, I think you may have something re' Zone Alarm. I had the same thing here.
Reading your post I checked mine, and it now reads correctly.
Like you the only thing different is the latest version of the firewall!!

$:-\$

BTW those getting 95% 'ish, I think your RWins are too low (if you're on MAX), you should up it to around the low 200,000. Say 201640 to start. Then try the test again.

HTH

Thar · Sep 09, 2006, 21:49:43

Thanks for backing up my suspicion MoHux.

Now I have that sorted I can experiment with the RWIN...

yamster · May 29, 2018, 20:40:32

I know this is a very old topic but I am on FTTC and have the exact same issue. I have double checked and taken my network kit and computers to another house and the MTU shows correct but at my house the MTU only comes up as 1460.

The issue with the MTU only being 1460 is gaming lag where I am behind other players and also website will not load correctly. I have contacted IDNet support so I am waiting for a response.