The test result above was done using DOCSIS 3.0 modem, XFinity Blast and thru 5 MHz Wi-Fi (802.11n).
See how IPv6 improves the download speed more than 3 times of IPv4 in download test?
I think of the reason is that with IPv6, we no longer need NAT on the router. So the router most likely bypassed the traffic and directly forward it from the server to my computer (using global IP address).
The latency also improves with IPv6. This might be caused due to the fixed size of IPv6 header, unlike IPv4. All other optional headers in IPv6 are moved beyond the header, so routers can forward packets faster.
