Wayne Stallwood wrote:
So it sort of looks like anything that involves data exchange over your MTU size fails, which sort of points to a very broken IP stack somewhere.
s/fails/is unreliable/
Ping tests "normally" (ie when things seem OK) show fairly high packet loss using large packets, say around 10-30% depending on the mood of the line. When it breaks I get 90-100% loss on large packets. In both cases I'll usually get 0-5% loss on small packets.
What are correct MTU/MRU/MSS values? I have 1500/1500/1432 at work, but MSS looks wrong to me. not entirely sure what MSS affects, though.
But given that you have got this on two different machines, with two different connections via two different routers I can't think why. Are there any commons between machines, same kernel ? same firewall configuration ?
Nothing in common that I can put my finger on. At both ends I have a LAN, but currently my home LAN is just a Win2k PC and DVD player, plus the (Linux firmware) router. (I have three of my "home" Linux boxes in the office. Almost all my tests so far have been on the office line since that's where I seem to live these days, indeed its where I am now.)
My office LAN has 6-10 Linux boxes of varying flavours, and a similar number of Win2k/XP machines scattered around. All suffer ADSL loss at the same time ("looks like the Internet's gone again" is a common phrase in the office right now). Ping tests I've been running from a RedHat box and a Win2k box, with no obvious differences in results.
According to http://usertools.plus.net/exchanges/mso.php?id=24202 there was a BT outage affecting "Peterborough MUX 001 & 002" tail end of September, and this affected both of my lines (based on searching for both exchanges at http://usertools.plus.net/exchanges/ and getting directed to the same faults page). So that gives me some common BT territory, although whether relevant I don't know.
I have a larger box of straws somewhere we can try clutching at..bear with me while I try to find it :-)
The bear will probably not be interested in the straws!
Ahh here we go, extra large Tesco Value pack....Can you ping from the linux router ? Can you do the ping large packet test from there to isolate everything else ?
Can't check from work but will do from home when I get there. I've just ordered another Linux firmware router (http://www.ebuyer.com/UK/product/90976) which I'll plug in at the office to test with when it arrives on Tuesday (if eBuyer deliver on time - a small possibility).