Will increasing MTU size the speed?

Posted on 2009-04-02
Last Modified: 2013-11-09
Hi Experts

Will increasing MTU size the speedup my broadband(PPPoE) speeds?

If Yes, How to do that ?

If No, Why can't?

OS: Windows XP Professional SP2
Question by:VINOD MORE
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Expert Comment

ID: 24047504

Author Comment

ID: 24047527
@ peter41

Thanks for settings, but will that increase the speed?

Slight confusion should I low down or increase the MTU size? to speedup?
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Accepted Solution

woolmilkporc earned 250 total points
ID: 24047647
for PPOE the maximum recommended MTU size is 1492. 1500 is normally the max size for internet connections - use 1492 to allow for the 8 bytes PPOE "wrapper".
Increasing MTU size will allow for more speed, as long as the maximum value any connection in the whole path can handle is not exceeded. In that case it will come to fragmentation, which will have an adverse effect on speed. That's because fragmenting packets at the sender's side and re-assembling them at the target will be time-consuming.
Setting MTU in XP requires editing the registry -

In the right-panel, create a new DWORD named MTU with the new value.
You can try to find a good MTU size by using ping with the -f (don't fragment) option and with -l [MTU size] set to different values.
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Author Comment

ID: 24047864

Pinging with 32 bytes of data:

Reply from bytes=32 time<1ms TTL=64
Reply from bytes=32 time<1ms TTL=64
Reply from bytes=32 time<1ms TTL=64
Reply from bytes=32 time<1ms TTL=64

Ping statistics for
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 0ms, Maximum = 0ms, Average = 0ms

OK i got this replay when i pinged the gateway?
What settings should i make in MTU size?
LVL 68

Assisted Solution

woolmilkporc earned 250 total points
ID: 24048012
As I wrote,
to experiment with MTU sizes, use the -f and -l flags of ping -
Start e.g. with
ping -f -l 1492 [target]
If you see a message saying that fragmentation was required, but the DF flag was set, the chosen MTU size is too big. Decrease it, until you find a size which will pass without an error. This is the maximal unfragmented (and probably optimal) MTU size for that particular connection.

Author Closing Comment

ID: 31565678

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