my MTU stuck at 1440

hocine · Post by **hocine** » Sat May 01, 2010 10:41 am

Hi guys,
whatever value i put in mtu (using tcp optimiser or even directly in the register or my router (cnet car2-801) the value remains the same mtu=1440.

i have xp pro sp3 and an adsl connection of 8Mbps PPPoe.

any help please?

« SpeedGuide.net TCP Analyzer Results »
Tested on: 05.01.2010 10:43
IP address: 41.227.xx.xxx
Client OS: Windows XP

TCP options string: 020405780402030302010101
MSS: 1400
MTU: 1440
TCP Window: 131072 (NOT multiple of MSS)
RWIN Scaling: 2 bits (2^2=4)
Unscaled RWIN : 32768
Recommended RWINs: 64400, 128800, 257600, 515200, 1030400
BDP limit (200ms): 5243kbps (655KBytes/s)
BDP limit (500ms): 2097kbps (262KBytes/s)
MTU Discovery: ON
TTL: 51
Timestamps: OFF
SACKs: ON
IP ToS: 00000000 (0)

Rollingstone · Post by **Rollingstone** » Sat May 01, 2010 12:12 pm

Have you set MSS also ?

hocine · Post by **hocine** » Sat May 01, 2010 12:22 pm

No!!! Well i thought that was done automatically... (oops)
Besides, I don't know how to set it specifically!

hocine · Post by **hocine** » Sat May 01, 2010 1:44 pm

@Rollingstone:
Well i don't understand why you asked me that question? I thought that MSS was linked to MTU... but your "question" led me to reconsider this and make new searches on the subject... Result, you wasted my time.
I don't know if you did it on purpose or if you are really ignorant, but what i know is that it's not a kind behaviour for a help forum!!!
At least i hope you laughed a bit!!! pffffffff

Rollingstone · Post by **Rollingstone** » Sat May 01, 2010 11:27 pm

Some modems that you must change them all ! Sorry for confusing a bit !

Try the following with TCP Optimizer:

General Settings tab:
Custom settings - check
Modify All Network Adapters - check
network adapter selection - your NIC
MTU - 1440
TTL - 64
Windows Scaling - check
TCP Receive Window - 128800
MTU Discovery - Yes
Black Hole Detect - No
Selective Acks - Yes
Max Duplicate ACKs - 2
TCP 1323 Options:
Timestamps - uncheck

Advanced Settings tab:
Max Connections per Server - 10
Max Connections per 1.0 Server - 10
LocalPriority - 5
Host Priority - 6
DNSPriority - 7
NetbtPriority - 8
Lan Browsing speedup - optimized
QoS: NonBestEffortLimit - 0
ToS: DisableUserTOSSetting - 0
ToS: DefaultTOSValue - 0
MaxNegativeCacheTtl - 0
NetFailureCacheTime - 0
NegativeSOACache Time - 0
LAN Request Buffer Size - 32768

hocine · Post by **hocine** » Sun May 02, 2010 9:08 am

Hi Rollingstone,
well i set things the way you told me to and that's the result :

« SpeedGuide.net TCP Analyzer Results »
Tested on: 05.02.2010 09:06
IP address: 41.225.xx.xxx
Client OS: Windows XP

TCP options string: 020405780402030301010101
MSS: 1400
MTU: 1440
TCP Window: 128800 (multiple of MSS)
RWIN Scaling: 1 bits (2^1=2)
Unscaled RWIN : 64400
Recommended RWINs: 64400, 128800, 257600, 515200, 1030400
BDP limit (200ms): 5152kbps (644KBytes/s)
BDP limit (500ms): 2061kbps (258KBytes/s)
MTU Discovery: ON
TTL: 51
Timestamps: OFF
SACKs: ON
IP ToS: 00000000 (0)

I then tried to set RWIN to 257600 which appears to be closer to my broadband, but it didn't work. it returned to a "non multiple of mss"

Rollingstone · Post by **Rollingstone** » Sun May 02, 2010 11:28 pm

HOw's the speed now ?

hocine · Post by **hocine** » Mon May 03, 2010 7:00 am

well for download i obtain a 845 Bps