Intermittent connection issues loading/changing site- secure connection failed/site can't be reached

[EDIflyer]

Is anyone else occasionally getting a 'connection down' error from Chrome (or 'Secure Connection Failed' from Firefox) when changing page - if I hit refresh it works fine. At first I wondered if it was the site I was using but have noticed it on multiple different major websites over the past couple of months and not noticed it from other locations where I don't use Three Broadband so does seem to be related to the router/connection (this is via wired Ethernet too, so not a WiFi problem).  I've tried changing DNS server in case that helps but no difference.

It mainly seems to happen when trying to first load a site or (annoyingly) at checkout when a different site is being loaded as part of the checkout process.  It certainly doesn't happen everytime but does happen with reasonable frequency.  I've also noticed I often get it when trying to pull/push from/to Github too and have to do so a number of times for it to work (browsing the Github website works fine).

I'm using a NR5103E with Firmware Version V1.00(ACBJ.0)b14 - I tried rebooting it but to no effect.

[AkiTaiyo]

Just had it happen again.. This time on sky.com.

Now there is an interesting coincidence here..
The IP address for inews (2.19.176.162) and the one for sky (23.57.166.79) are both served from an Akamai data centre. 
Does that mean that Three's network doesn't play nicely with Akamai's infrastructure?

[AkiTaiyo]

Another failure, this time at visualstudio.microsoft.com..  Once again, served from Akamai..

[AkiTaiyo]

With visualstudio.microsoft.com, the failure rate is almost 1 in 5 attempts, which is terrible..
Three needs to fix this ASAP..

[AkiTaiyo]

Failed to load their own f'in website..

[AkiTaiyo]

New information.. Looks like the problem exisits somewhere between Three and Akamai..

If I manually change my DNS entry for visualstudio.microsoft.com to a different Akamai server (104.123.88.60), I can repeat the abolve connection test repeatedly, with ZERO errors..

Difference being that IP-Geolocation shows the new IP to be at a UK based Akamai datacentre, rather than the Ireland based datacentre..

Because of the way these CDNs work, I don't think theres a nice way to change from one to another.  Maybe using a purely UK based DNS resolver.. I'll try this next, currently I run my own resolver based in Iceland.

[EDIflyer]

Good detective work, @AkiTaiyo! Presumably this is why using a VPN is helping too as the routing to Akamai is being tunnelled and occurring elsewhere rather than between Three and Akamai.

@JonathanB hopefully your senior technical folk can look into this additional info???

[wgen]

The issue occurs for me with websites also hosted via AWS and other cloud providers, so it's nothing to do with Akamai. (Have checked for Akamai routing in traceroute also)

[AkiTaiyo]

Changed my DNS from my own resolver to use Cloudflare with Quad9 as backup.. No more problems with any of the sites I've been having regular issues with..
From my limited testing, these were all served from Akamai, but if wgen has also seen the problem from other CDNs, then a DNS change might not be a complete solution.
If anyone has a non-Akamai URL that fails regularly (I was using visualsudio.microsoft.com because it failed so frequently!), I can also test the URL through Three and other connections to see if is a similar issue with different data-centers.

[bytespider]

DNS did nothing for me. I've had some success with disabling IPv6 features including DHCP/RA but that's anecdotal as I've not browsed much to be able to notice of it's helped  

[AkiTaiyo]

Yeah, the DNS change has only affected some sites.  I keep coming across more failing sites the more I browse. 
I also have all IPv6 features turned off on the router.