I have a problem with loading one site (removed the name in order not to advertise) from my PC. Actually this problem appeared with several different sites. 'Help centers' of those sites usually reply something like 'we can not reproduce the issue'.
Use case:
OS Ubuntu 15.10, tried Google Chrome (v.48.0.2564.109, 64-bit) and Mozilla Firefox (v.44.0.2).
My question: is there any ways to find out the cause? Tried to search, but all the solutions were related to specific browsers and were fixed after update.
What I also tried to do:
Could that be a problem with my network or internet provider?
The problem was due to a unfavorable automatically choosen MTU mtu discovery, that lead to fragmentation. As the page did not allow fragmentation the connection failed (ICMP can't fragment - type 3, code 4). After decreasing the MTU form 1500 to 1440 all problems were gone.
On Linux:
ip link set dev <dev> mtu 1400
or
ifconfig <dev> mtu 1400
On Windows:
netsh interface ipv4 show interfaces
netsh interface ipv4 set subinterface <devIDX> mtu=1440 store=persistent