Question About MTU and What The Best Level is

[ethan103]

Ok, i have been hearing quite a lot about this.

The defualt is 1500 MTU.

But i heard that setting it to 1470 will give you much better packets results as in its more efficient for such things as online gamming.


Can anyone clear this up?

[Sephiroth]

To my mind, if your current MTU (1500) is larger than the minimum required by a gaming packet, you're safe and there is no inefficiency. Problems arise if your NIC interface MTU is lower than that recommended for the game.

Game recommendations are founded on the fact that ADSL and Cable architectures support different maximum MTU values. Since 1500 is > than the ADSL value, I don't think you have any MTU issues.

What do others think?

[ethan103]

Well Since im on a modem, could i change it anyway?


And i can across this:


1500 is the maximum packet size of the internet and also what most cable companies use.
However 1500 is set for the best SPEED possible not necessarily efficient packet size.

Your megabytes and kilobytes of your speed are in octets which is universally (8) bytes.

Each cell contains 48 bytes of data. With the above calculation of 98x15=1470

1470/48=30.625
1372/48=28.58333333

THEN you times by 8, which are the octets which make up your bandwidth.

1470/48=30.625x8=245
1372/48=28.58333333x8=228.6666667

what does mean?

well with every multiple of eight 30.625x16 or x 24 x32 x64 etc.. is an WHOLE number.
meaning every megabyte,kilobyte,etc.. is OPTIMIZED.

HOWEVER 28.58333333x16 x 24 x32 x64 etc.. are not WHOLE numbers.
meaning <1% of your bandwidth is going to waste.

what does this mean?

So to sum this up
1470 MTU is the optimal speed & packet size for cable users, all-in-one.

[Matthew]

I have mine on 1400 on my ADSL connection as I found I could not connect to the net if it was higher.

[BloodyL]

When I was on XP Pro x64 I had to specify an MTU of 1496 in my router otherwise Windows Update would always fail to load.
I've kept the value at 1496 even though I've moved over to Win7.
Having read the above explanation I think I'll try 1470.

Cheers!

(Running with the above calculations, 1500/48=31.25*8=250, so the 1500 MTU is a valid value.)

[downquark1]

You can use an app called mturoute to identify the optimal value. Just use it on an external server like the bbc

[BloodyL]

Having done a run through with mturoute, 1470 does indeed seem to be the right spot for my local hub. :)
+rep all round.

[ethan103]

Can you change your MTU on a Modem? (VM 50Mb one)