Merlin wrote:
>>If you put mtu in the news archive search at www.adslguide.org, you will
>>see that the problem that setting 1458 worked around was fixed in July
>>2003.
>>
>>If you want a slight tweak then 1478 is optimal for pppoa/vc mux which
>>most people in the UK use.
>>
>>Do not change your router (unless it has defaults that won't work with
>>1500 MTU). If you want to tweak then change the MTU on each computer.
>>
>>Andy.
>>
>
>
> Thanks Andy,
> That is where I am going wrong. I have been changing the
> setting on my netgear router (DG834g) as I thought this was the problem.
> I have 2 laptops that have trouble connecting with wireless netgear cards.
> Works for a while then drops out. Distance approx 7 metres.
> Can I change the laptop settings manually or will I need to use the
> 'fix'?
>
If you are using windows then you can use this -
http://www.dslreports.com/drtcp
It may be worth setting rwin aswell I don't know what to suggest for you
, I use about 32k - the exact figure being worked out so that it's a
multiple of MTU - 40.
I don't use wireless myself, but if you think that the poor performance
you see is down to packet loss rather than loosing connection then
reducing mtu down to 500 ish could help because a shorter packet has
more chance of surviving (I have read that some (all/any?) wireless
drivers already try this trick at link level, though).
To choose an efficient mtu it needs to be integer divisable by 48 after
you have added 10 to it. 566 is efficient as 566 + 10 / 48 = 12, 567
would use an extra 53 bytes on the wire to send the extra byte. 565
would use the same on the wire as 566 so you only loose 1 byte etc.
Unless you are into Linux I can't think of anything else you can do with
tcp to get around high loss - if that is the problem. You can see if you
are getting lots of packet loss at tcp level when uploading ftp/big mail
etc. by keeping an eye on the retransmitted segments count in netstat -s
output.
Andy.
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