* Ez mail > Since I have no fr**king clue what could the problem be, I'm trying on > this list :)
I concur 100% with Erik's assessment that this in all likelihood is a PMTUD problem, specifically in the web_server->your_desktop direction. I'd just like to add that the fact that you see it happening to several independent websites that are known to be operated by competent staff, and that the problem comes and goes, further indicates that it is due to rate-limiting of ICMPv6 PTB replies from your tunnel broker's tunneling router/server. The ICSI Netalyzr (http://netalyzr.icsi.berkeley.edu/) will give you very useful debugging output from the outside point of view. You might have to run it a few times to to reveal the MTU blackhole though, due to the problem's intermittent nature. As Erik mentions, lowering the TCP MSS will likely work around the problem. You can probably do this by having the RAs your router emits to the LAN advertise an MTU of 1452 to match your tunnel (which in turn should make your desktop default to a TCP MSS of 1392), and/or have your router rewrite ("clamp") the MSS value in TCP packets it forwards to/from the tunnel to 1392. Or, even better, get rid of the tunneling crap and get native IPv6. This is a very common problem for IPv6 tunnels. As a web site operator I would actually prefer it if people stayed IPv4-only until their ISP could provide them with properly supported IPv6 connectivity. Oh well... Tore
