@spoonbard Yes if you could monitor it with the 1452 setting for 24-48 hours and report error figures it would be appreciated, if you could then also test with whatever the figure was before the change for another 24-48 hours that will help with comparing things.
@babis unless i remember wrongly (more than possible lol) you are in Greece, i have no idea what the default MTU is for most ISPs out there, in the UK most (NOT all) can get away with something between 1460 and 1500 FOR ADSL ONLY. Many can have a full 1500 set on ADSL. Overseas this may be entirely different. Either way in your experimenting keep it above 1400, anything below that will normally hinder rather than help. Make small changes no more than a difference of 10 at a time.
^^^^ All that figure wise is for any ADSL readers.
Any change you make it is best to restart the computer, this SHOULD ensure windows TCP does not try to send anything over the MTU size you set in the router.
Doing a ping test like say......
Code:
ping www.google.com -f -l XXXX
where XXXX is the MTU figure you want to test if you are on later versions of windows is pointless in many cases as the TCP in that auto-negotiates so any figure that says it can manage is normally a lie, typically it wll say it can manage everything up to 1500, which on FTTC at least i can say for a fact is a fib as PPPoE does not support MTUs that high. Typically that commonly known test is only 100% accurate in Windows XP/2000 and earlier.
ANYONE on Windows XP can or should be able to use that above trick to find the MTU, though if you are FTTC and it says you can ping with a 1500 setting it is lying.
MTU for anyone reading is basically maximum transmission unit (MTU) If your MTU is too large in size it can lead to retransmissions if the packet encounters a router that can't handle that large a packet. Too small an MTU size means relatively more header overhead and more acknowledgements that have to be sent and handled.
A MTU too large will possible mean errors, typically it affects CRC for many from my experience of deliberately setting it way too high, but i suspect on the Asus due to how inaccurate the errors are reported this may be affecting the FEC count also or at least be contributing to its high figures.
On windows XP and earlier you could set MTU and other connection related settings manually in the OS but on windows vista, 7 and 8 (which i assume most are using now) they have a new TCP (Transmission Control Protocol) which adjusts on the fly. Sometimes this does a poor job at setting a correct RWIN figure (TCP receive window) which can lead to errors. Most devices will handle this fine, but i suspect based on some of the things ive seen in this thread the Asus maybe does not. Thus setting it lower should help (just do not go stupidly low, keep it above 1400).
The 1452 MTU setting for FTTC is a suggestion from the BT homehub 3/Openreach modem combo supplied days which while not very feature rich was in general reliable for FTTC. Its what im currently using and it will not allow me to set anything over 1452 even though ping testing will allow packets at 1500. (again windows TCP auto negotiates so technically its fibs)
Typically you want MTU to be as large as you can get it without retransmissions the only real way to find that out is constant small tweaks and testing. 1452 on FTTC should be probably the best for most people. If you are really attetive you will notice certain sites will load every so slightly faster or slower with MTU adjustments, normally you will see this better on a site that typically loads slow by default (IE it will get even slower or faster depending on MTU).
Anyways its something simple for everyone to have a try and report findings and easy enough to put back should it make no difference. Hopefully it does help, though again im not promising or even that confident it was just more of a hmmmmm thought and worth a go feeling.
