FTTP (Full Fibre 900) download being throttled when VPN connected

[Fractal_Fragger]

Hello,

OK, here goes. I have BT Full Fibre 900 so should be getting up to 910Mbps download speed. On my normal machines at home I am getting around 850Mbps which is brilliant. However I, like countless others are working from home. So my machine is connected via Cat6 ethernet to my router and I have an always on VPN using Any connect (split tunnel for machine and user based connection). 

The issue I have have is that when i perform a speed test on my work machine i can barely get past 20Mbps. Now i can understand some loss in speed when connecting to VPN due to encryption but this is a massive loss in speed (80+% i think). 

Why is this? Oh I have run multilple test at different times of the day all on LAN and with all my other devices off. This is not internal/ my employer as no one else is having this issue and i am actually in my employers IT department so i know we are not throttling VPN connections.

Thanks in advance

[garybs29]

BT do not throttle connections, end of. Obviously an issue somewhere that needs looked at

[Fractal_Fragger]

Bit of an arrogant response if you ask me  @garybs29 .

Is not as got put it, end of. I have asked a genuine question and I do not need a childish reply. I have also used services such as  nordvpn, purevpn, expressvpn, and many other vpn services on my  home service and they have the same issue but when used on other ISPs such as Virgin sky, talk talk it did not have this issue. You have been very quick to say no but have no hard evidence to support it. I dying have solid proof but it seems rather odd that I only suffer with this issue when on my own BT connection.

As I stated before, I work in the it department of my employer and have had connection that is not our infrastructure capping or throttling vpn connections. ISPshave been known to do this in past years to residential customers as they should not be using home broadband for work purposes(bt included), however we no longer have this separation due to covid and working from home is now the norm.

So I am asking again can someone answer my question and if it's a no please provide here evidence to support your claim

[garybs29]

It's not arrogant it's the truth. If you search for throttling on here you'll see others advising that BT don't throttle connections

[busterboy1]

I completely agree with @garybs29 

Have a read.

https://www.bt.com/help/broadband/bt-s-approach-to-broadband-traffic-management

[Fractal_Fragger]

@garybs29 So you work for BT then as I can take this as an official response? I have worked in the IT industry for almost 20 years and what ISPs say and what they do are two different things.

A acceptable reduction (around 20%) would give me speeds of around 680Mbps. However, im getting a maximum 20Mbps when on VPN using BT, that's a whopping 97.6% reduction in speed at minimum.

I have two other colleagues using BT FTTP and the rest of our IT department are on FTTC packages with other suppliers, yet myself and the two others on BT are having this exact issue! We are in three different locations so are connected to three different exchanges. Not one of us three can get above 20Mbps when connected to our employers VPN (AnyConnect) yet our other colleagues on slower FTTC packages are getting roughly 55-65Mbps when connected to VPN on packages of 80-100Mbps.

So please don't tell me that BT are not capping or throttling the connection when every test i do returns identical results.

[garybs29]

No, I don't work for BT, most of the people on here don't only the mods.

I'm talking from experience though, I've been working from home since April on my BT connection using a VPN & haven't experienced any throttling & I'm sure lots of other people have as well. The link provided by @busterboy1  as well also advises that BT don't throttle connections so I don't know what your issue is but it's not throttling

[scottrc]

I dont know much about VPNs etc but BT doesn't throttle speeds. The TCP protocol itself can if it detects packet loss and high latency. When you do a speed test, does it start off high for a second or so and then drop down? Or is it a constant slow? If it starts high, even for less than a second, its probably that. Maybe something in the hub firewall purposefully not responding, or slowing responses to prevent floods of unwanted traffic, that would in turn slow throughout. Check the hub technical logs and look for blocks etc. That would be the best source of info if it is the hub. My amateur guess would be the smart hub firewall, so you could test it by disabling it and reconnecting to the VPN and test again. Don't forget to reenable though.

Is DTLS enabled for AnyConnect? I just read about that on reddit. 

Mlabs is a good speed test as it will show retransmissions. 

I'm guessing there is a big list of reasons for this and I really don't know much but hope something I've given helps narrow it down.

You could also try a tracert on both machines to check for routing errors.

[Raymaker]

Hi I have exactly the same issue if I connect a Router set to Access point mode and attach it to my main FTTP router the connection will reduce to 20mb/s and below, when I remove this within 30 minutes the circuit will just ramp back up for 500mb/s This is very odd behaviour. It does look like throttling if it is not why does it happen. It looks  like BT are assuming I’ve shared my network with another house and are throttling me.  When I use mesh routers it does not throttle the connection. 

[adam_101]

I also have the same issue. Recently upgraded to BT Full fibre 900 (previously on 100). When I connect the BT smart hub 2 router directly into the modem I get 500-600mb download speed, however when the data is fed through a cat7 cable and I plug the router in the other end it drops to 20-50mb. Any ideas why this would happen? 

This thread hasn't come up with many constructive reasons as to what could be causing this issue we are facing, so posting here again in the hope that we can attract some helpful insights to what must be causing it.