Something wrong there. Are you testing directly wired up to the ONT (bypass any BT routers etc)

I'm glad someone agrees.

I've bypassed the BT router for testing and saw no difference, went straight to the ONT and set up a PPPOE connection on the computer I was testing from.

I can hit between 700-800 Mbps on single thread on Openreach FTTP using TTB. Through all my network.

Yeah I'm not getting anywhere near that on a single thread, normally around 20MB/s.

Ping times seem on the high side too. I'd expect around half that (although not if your hitting a server in London from Scotland say)

Ping will be a bit higher as I am going NE Scotland->London or France or Germany or Netherlands for the tests.

How would you proceed with a complaint like this?
I've had no luck with BT, or Openreach.

I documented what has happened so far here: https://community.bt.com/t5/BT-Fibre-broadband/Slow-...

The first post will be confusing, as I now know it's single-threaded performance that is the issue, but I thought I had ruled that out using a windows build of aria2 and trying 8 threads, which didn't work at all. I figured it out later.

Edited by kst (Thu 26-Aug-21 22:35:28)

Have you tested using another machine/NIC combo?

There may be other congestion, and I know that some folks in the past (not necessarily on BT Retail though!) who were experiencing sustained slowdowns, have requested from their service provider that BTW move their connection to a different SVLAN, which had less congestion.

I documented what has happened so far here: https://community.bt.com/t5/BT-Fibre-broadband/Slow-...

If I were you and the others are fine I would maybe refer to this thread as it is a very reputable site forum with a variety of experts from all over then country and world.
I always noticed twitter is a good place to complain when there is an issue as things seem to get fixed then. Up to you but it worked with Virgin media for me once, got an engineer appointment next day (for them that's about how long it would normally take to get off the hold music)

In reply to a post by Ad_G:

BT Full Fibre 900 here, lowest single threaded seen was 610Mbits/s, highest 790Mbits/s. Similar results on both IPv4 and IPv6. Multithreaded is normally close to 900.

What does your TBB speed test graph look like? That can give clues on what the issue might be.

Also 900 here, this speedtest below is typical: Had it for a year or so, and single thread has improved a bit, used to be 200 at one point.

Your images are not working for me, but I took a look at them on the BT side.

As you have a ramp up followed by a peak and then it dips back that is tending to imply congestion or very slight packet loss somewhere on the path. Are you able to run a probe to you servers to see if you can see any sign of packet loss? Pathping etc might help but as modern routers tend to de-prioritise ping it can give a false result.

One other thought as you mentioned being in NE Scotland (probably explains your latency being twice mine), have you looked at TCP window size configuration? The three things that are generally the case of single TCP thread are generally congestion, packet loss and latency/window size. With your latency are you maxing the window size? If so whilst there is still bandwidth free the server is waiting for ACKs before sending any more data.

From a quick check if you have a TCP window of 64Kbyte then then with 23ms of latency you are at around 22Mbits/s. Worth a look a the settings on your machine/server and if possible look at some packets to see what the window size is running at during the download.

What you can hit in another location is not relevant to someone else. Like I said in my post I could only hit around 300Mbits/sec on single threaded tests to Thinkbroadband for many months with IDNet, it was actually a bit slower than Cerberus 330 service I left on single thread tests, until all of a sudden it's over double that, and nothing changed my end, not even a drop in PPP. Links get upgraded, links get congested.

It is a CONTENDED service, no one is guaranteed 900Mbits/sec. If the ISP considers the speeds below whatever guarantees they sell them at, then at least you can leave and try another ISP.

I would suggest to the OP to make sure to perform tests via IPv4 to get a more like for like with Virgin, as IPv6 has a bit more overhead or might not be so well optimised on their system/router for some reason, and there is an IPv4 speed test button on Thinkbroadband.

If everything is okay on their system no amount of our help or suggestions is going to resolve their problem. We don't pay for an uncontended service with these products, slow downs are all part of it, hence the guaranteed minimums are way lower than 900Mbits/sec.

Those speed tests seem to be showing congestion somewhere. Try clicking on the Analysis button and see what it says about buffer bloat, and compare with an IPv4 test which I've always found gives me the faster numbers on speed tests.

You are buying a contended service, some people are lucky and get top speeds most or all the time, some of us go over more congested routes. Yours seems particularly congested but I'm sure it will just suddenly resolve itself as new capacity gets added. Virgin media has these problems quite often as well, just you didn't, horses for courses.

Maybe see if you can agree with the ISP to give it 60 days and if things are not improved then they allow you to still leave and cancel the contract.

Definitely worth setting up a BQM to make sure you have no packet loss going on, and this also may show up the congestion and times it is happening.

Edited by E300 (Fri 27-Aug-21 10:06:02)

In reply to a post by E300:

I would suggest to the OP to make sure to perform tests via IPv4 to get a more like for like with Virgin, as IPv6 has a bit more overhead or might not be so well optimised on their system/router for some reason

IPv6 actually has less overhead because there's no NAT involved and the connection is completely end-to-end. I see this reflected in latency too (although that could also be down to different routing...).

In reply to a post by E300:

What you can hit in another location is not relevant to someone else. Like I said in my post I could only hit around 300Mbits/sec on single threaded tests to Thinkbroadband for many months with IDNet, it was actually a bit slower than Cerberus 330 service I left on single thread tests, until all of a sudden it's over double that, and nothing changed my end, not even a drop in PPP. Links get upgraded, links get congested.

It is a CONTENDED service, no one is guaranteed 900Mbits/sec. If the ISP considers the speeds below whatever guarantees they sell them at, then at least you can leave and try another ISP.

I would suggest to the OP to make sure to perform tests via IPv4 to get a more like for like with Virgin, as IPv6 has a bit more overhead or might not be so well optimised on their system/router for some reason, and there is an IPv4 speed test button on Thinkbroadband.

If everything is okay on their system no amount of our help or suggestions is going to resolve their problem. We don't pay for an uncontended service with these products, slow downs are all part of it, hence the guaranteed minimums are way lower than 900Mbits/sec.

I know it’s contended. I’m not stupid. There is precedence, as you probably are aware as a former Cerberus customer, if folk requesting and getting moved to another SVLAN. Whether BT Retail will take that up with Openreach is debatable as they aren’t a business focussed ISP. But it’s something that could be explored.

In reply to a post by aidanh:

In reply to a post by E300:

I would suggest to the OP to make sure to perform tests via IPv4 to get a more like for like with Virgin, as IPv6 has a bit more overhead or might not be so well optimised on their system/router for some reason

IPv6 actually has less overhead because there's no NAT involved and the connection is completely end-to-end. I see this reflected in latency too (although that could also be down to different routing...).

That depends on your definition of overhead.
What exactly do you mean by less overhead because of no NAT?

When discussing packet overhead IPV6 has a larger header overhead at 40 bytes compared to IPV4.