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.

[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???

[AkiTaiyo]

Failed to load their own f'in website..

[AkiTaiyo]

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

[AkiTaiyo]

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

[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]

Sadly it was just coincidence..   After spam loading a bunch of pages I started getting some failures again.

Whats interesting is there doesn't seem to be any suitable explanation for it from the wireshark logs..
Here's a side-by-side of a connection to inews, one fails and one works.

The first picture shows the log from the failed attempt.  The curious part of this is that at *exactly* the same time as the 'window update', a FIN is sent from the server to close the connection.
Compare this to refreshing the page, which loads correctly

The opening sequence is identical... Except that WireShark identifies the working session 'Hello' as TLS v1.3, where as the failed session it identified as TLS v1.  I suspect this is a identification discrepancy with wireshark.  The details both show the same version IDs. 
Not sure from here, if anyone has any more insight on this I can provide these two sessions as wireshark files. 
The oddity for me is the FIN coming in, initiated by the server end.

[AkiTaiyo]

After a bit of playing around in Wireshark with some sites that were intermittent..
It looks like the issue might be related to sites that use the QUIC protocol.  This is a UDP based transport on port 443, as apposed to the usual TCP based.
As an experiment, I've configured my firewall to block all UDP traffic on 443..  So far, no more 'end of file' errors..
Will see how it goes, or maybe just a coincidence. 

[fashric]

Interesting, could you keep us updated on how that goes.

[AkiTaiyo]

Good call to change provider I would say.  Three seems like they have no priority to fix this and seem to be hiding behind the terrible excuse of 'it doesn't happen to us'.
I'm almost at the point of moving provider despite only recently changing from a monthly to a 24mth.. At this point I don't care, I'm just fed up with apps not working and pages not loading.
Really not helpful when you work from a home office.

[Chrisrkilv]

Well, I've called it quits.

Today, Nabu Casa URL decided to take a siesta, and that's my line in the sand.

But hey, BRSK dropped by at just the right moment like a guardian angel, announcing full fiber 900mbps up and down coming to our street in July. So, I took the chance to bail on my contract and managed to avoid avoid the £370 cancellation fee due to the (lack of) service.

Now, I'm on a monthly rolling EE 5G Unlimited Data plan for £26.50. Put the sim into the Zyxel NR5103E from Three, and voila! Everything's magically fixed. Nabu Casa is back online, Home Assistant Updates are working, and even git is playing nice with Github & ghcr.io. a proverbial middle finger to the technicians who blamed my modem for the past two months! .. and I can still port forward! yay!

Spoke to Three on the phone who told me they charge £105 for the Zyxel modem if you decide to keep it. Quite a bargain for a clearly functional 5G Modem, i'm going to keep that and use it with EE's sim until BRSK come arround (And for whatever reason they don't, I have a solid connection that i'm no longer tied to for multiple years)

For anyone stumbling upon this post, call them up, bail on your contract siting the issues listed here. Keep the modem (or grab a Huawei 5G Modem), and grab an extra Monthly rolling Unlimited 5G data plan with your phone provider. Liberation from Three is within reach!

Cost to exit Three = £0
Cost of the modem = £105
Cost of a new EE Rolling 5G Contract £26.50 PCM
Cost of a BRSK 900 mbps up down fibre connection with static IP = £37 PCM
Cost to not have to speak to Three's awful, crappy, Indian Outsourced customer, technical and complaints department ever again = PRICELESS!