Website performance is slow using BT Internet but VPN fine

General
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Website performance is slow using BT Internet, however using the same network with a VPN is fine.

The chrome browser shows the requests as ‘stalled’ when downloading several small images from the website.

I have tried several different PC’s and MacBooks and same issue.

This is only happening on BT Internet.

3
  1. Can you share your ISP’s AS number?
    The AS number can be found here:
  1. By mentioning BT Internet, my first guess would be United Kingdom for the country.
    But can you share what state/region you’re seeing these issues in?

This would suggest some issues within BT’s network, such as for example congestion within their network.

4

AS Number 2856

Yes I am connecting from London in the UK.

I have now discovered that it is an issue with IPv6, I have disabled IPv6 and the website works fine.

Does any know why IPv6 would be causing the issue?

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It looks from a couple of tests to me like AS 2856 is sending traffic, both on IPv6 and IPv4, towards Cloudflare’s PoP in London (LHR).

IPv6 and IPv4 are two different IP protocols that don’t talk to each other, - like two different worlds.

IPv6 has since 1996 been supposed to take over, some ISP’s are quick, but others are slow, and even some doesn’t want to have to do with IPv6, for various reasons.

It happens that some (typically larger) provides are refusing to set up settlement-free peering with Cloudflare (and/or other hosting / content providers); which can cause very weird routing to happen, including traffic that travels through both different countries, but also towards different continents.

However, this doesn’t seem to be the case with AS 2856.

Interesting enough, even though it isn’t a lot of a difference, latency seems a little bit lower on IPv6, than it does on IPv4 at the moment, when from AS 2856 towards Cloudflare.

I would probably rule it out as (hopefully) some temporary congestion, maybe because BT has many customers, and that they haven’t been good at upgrading their connections to ensure the proper amount of capacity compared to the flow of traffic their customers are making.

Seems like BT’s own community forums are filled with people from time to time, that are talking about congestion issues, including in e.g. evenings and otherwise peak times.

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