Intermittent transfers through Virgin Superhub [SOLVED]

tony359 wrote:
...There is something I don't understand though: when running the tests, what am I actually testing? Am I testing my ISP network? Am I setting the proper MTU so my network has the best possible MTU suitable for my ISP network?...

Though I think you've sorted it, I'll answer anyway.

When you probe the MTU with ping, you are finding the MTU (maximum transmission unit) for that specific network path. That is why the VPN gave you a different value. (VPNs are usually lower because the packets are encapsulated as part of the tunneling, so the packets sent on the VPN link are larger than the original source).

So if you test the MTU by pinging the NAS from a home PC, you are testing the local network path between those devices. Results might be different for WiFi than they are for wired ethernet. If you test the MTU by pinging google, you are testing your ISP (and your local network, and any other ISPs on the route between you and google).

As far as setting the MTU goes, generally you don't want to set it below 1500 unless the physical network requires that to avoid IP packet fragmentation. If your ISP says you need 1492, then it is reasonable to match that on your local LAN.