Happy Eyeballs
"Happy Eyeballs" is an algorithm where IPv6 and IPv4 are supposed to co-exist, with IPv6 being chosen automatically over IPv4. "18% of Alexa’s top 10,000 websites are faster over IPv6 than IPv4. 91% were, at most, only 1 millisecond (ms) slower over IPv6 than IPv4. Happy Eyeballs (also called Fast Fallback) is an algorithm published by the IETF that can make dual-stack applications more responsive to users by determining which transport would be better used for a particular connection by trying them both in parallel.
The algorithm and its requirements are described in RFC 6555, “Happy Eyeballs: Success with Dual-Stack Hosts”."
And
“The proposed approach is simple – if the client system is dual stack capable, then fire off connection attempts in both IPv4 and IPv6 in parallel, and use (and remember) whichever protocol completes the connection sequence first.”
Therein lies my problem.
Even though my ISP supplies my 500Mbps fiber optic connection they do not yet support IPv6, so I use a Hurricane 6to4 tunnel for IPv6 connectivity. I set this tunnel up while using 16.04 and continued it through 18.04 and regularly check it using the dual stack mode at testmyipv6 it always showed that IPv6 was the default, with fallback to IPv4 after 1 second. While running K18.04 I set up an ipv6-service for systemd and it continued using IPv6 as the default. After installing K20.04 my previous and current FireFox (78.0.2) browser frequently switched on its own to IPv4 as the preferred IPv protocol. I checked all the appropriate about:config settings, which were correct, and the settings in /etc/gai.conf as well.
Following boot up or reboot the browser randomly selects either protocol. If it selects IPv4 as the default then I close the browser, recycle the power on my printer, and retest testmyipv6 . Sometimes, strangely, that fixes the problem. If it doesn't then I open a Konsole and issue "sudo systemctl restart ModemManager". That often fixes the problem. So does logging out and logging back in without rebooting. But, usually, either recycling the printer or issuing the ModemManager restart restores IPv6 protocol preference.
Once I have IPv6 set as the preferred protocol it usually remains that way for the rest of my browsing session. However, on more than one occasion I have noticed that after browsing for a while the preferred protocol gets switched back to IPv4 and I have to resort to the above measures to get it back to IPv6.
Overall, I'd say My Eyeballs are not happy.
The algorithm and its requirements are described in RFC 6555, “Happy Eyeballs: Success with Dual-Stack Hosts”."
And
“The proposed approach is simple – if the client system is dual stack capable, then fire off connection attempts in both IPv4 and IPv6 in parallel, and use (and remember) whichever protocol completes the connection sequence first.”
Therein lies my problem.
Even though my ISP supplies my 500Mbps fiber optic connection they do not yet support IPv6, so I use a Hurricane 6to4 tunnel for IPv6 connectivity. I set this tunnel up while using 16.04 and continued it through 18.04 and regularly check it using the dual stack mode at testmyipv6 it always showed that IPv6 was the default, with fallback to IPv4 after 1 second. While running K18.04 I set up an ipv6-service for systemd and it continued using IPv6 as the default. After installing K20.04 my previous and current FireFox (78.0.2) browser frequently switched on its own to IPv4 as the preferred IPv protocol. I checked all the appropriate about:config settings, which were correct, and the settings in /etc/gai.conf as well.
Following boot up or reboot the browser randomly selects either protocol. If it selects IPv4 as the default then I close the browser, recycle the power on my printer, and retest testmyipv6 . Sometimes, strangely, that fixes the problem. If it doesn't then I open a Konsole and issue "sudo systemctl restart ModemManager". That often fixes the problem. So does logging out and logging back in without rebooting. But, usually, either recycling the printer or issuing the ModemManager restart restores IPv6 protocol preference.
Once I have IPv6 set as the preferred protocol it usually remains that way for the rest of my browsing session. However, on more than one occasion I have noticed that after browsing for a while the preferred protocol gets switched back to IPv4 and I have to resort to the above measures to get it back to IPv6.
Overall, I'd say My Eyeballs are not happy.