Fibre 80/20 speed expectations

[#1]

Hi Plusnet team and forum,

I've had a ticket (195816868) open for a while with the support team discussing the speed of my connection.

My house is very close to the green cabinet (line test is reporting ~136m and we can see from the window!) and yet I don't seem to be able to exceed ~70Mbps down. My upload is ok maxing out at 18.7Mbps (~93% of 20Mb) but download I can't seem to improve.

I've tried replacing the ECI modem I was originally issued with, trying a Huawei HG612, Vigor 130 and now a Zyxel. None of these have made any real difference to the download I'm able to achieve. The line is quiet with no noise and nothing else plugged in.

My sync speed is good:

Max: Upstream rate = 26071 Kbps, Downstream rate = 102334 Kbps
Bearer: 0, Upstream rate = 20000 Kbps, Downstream rate = 79999 Kbps

And the SNR is solid:

           Down Up
SNR (dB): 11.3 10.6
Attn(dB): 7.4 0.0
Pwr(dBm): 13.0 -12.8

So my question would be what is the max actual download rate that can be attained with an 80/20 vdsl connection?

I've had friends and colleagues mention 75/76 down but I'm not able to get close to that even though I'm much closer to the cabinet than they are and also have a much better signal stats than they do.

Is 75/76 a pipe dream?

Thanks!

N

[#2]

Hi @ncd,

This all depends on the quality of the line, which can change and fluctuate over time. In theory you should be able to reach up to around 76Mbps based on the package we offer, though that is dependent on the estimated speeds for your line.

[#3]

@TheMightyAJ thanks for your reply.

What factors could affect the max speed? I have really good signal to noise ratio and the connection is rock solid so I wouldn't expect DLM to be kicking in.

I'm synced at 80/20 but hey can't achieve more than 70 on the download.

Apologies for the 101 questions! I'm keen to get the max out of what I have especially when I'm so close to the cabinet.

[#4]

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@ncd wrote: What factors could affect the max speed?

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Crosstalk is usually one issue if you are not achieving max throughput. Mine took a dive as more and more people locally took up fibre. In the heady days, 78mb was what I got on the various speedtests sites. Then it slowly sunk. School holiday times was good as the various families went away, so the download speed improved.

While it is nice to have max through put, is it really making that much difference? I just came to accept what I got coming down the wire. I've even stopped (for the most parts) doing speed tests!

[#5]

@idonno thanks for the info re crosstalk. I'm guessing there is little we can do on this?

You're right that most of the time it makes no real difference to me but I have just moved backup provider so have had to resync a lot of data both up and down so a few extra mb makes a lot of difference in terms of how long it takes for each dataset.

[#6]

Crosstalk affects sync speed, not throughput directly.

Throughput can be affected by other traffic, either from other applications on your laptop/PC, or other devices on your network.

That said, you won't get too much more throughput when testing, but make sure its from a wired port, switch wifi off.

[#7]

@ncd , out of interest, do you have a static IP address?

[#8]

@Mustrum - Thanks! 

Sync speed is good - 79999/20000 so almost 80!

For the purpose of these tests I've been connecting a host directly to the router (which is good for ~1Gbps). Wifi is not on this router. I've also tried establishing ppoe directly from a host to the modem to see if that helps. It doesn't! I've also done a packet capture whilst testing to confirm there is no other traffic during the test.

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That said, you won't get too much more throughput when testing, but make sure its from a wired port, switch wifi off.

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What do you mean by not get much more? Is there different a theoretical limit? From my recent reading I was under the impression that the maximum possible throughput was around 96.8% of sync speed which would take me to ~77Mbps as a maximum possible. That additional 7Mb or 10% would make a difference of several hours on my sync back to home!

[#9]

@Kevin - I do yes, I really hope this doesn't affect things!

[#10]

Unfortunately, yes it does. My current sync speed is 85 ish Mb and my max download speed via all the different speed testers is only 69Mb.

It's something to do with the way the Plusnet profile system handles static IP's.

This is from a post by @ejs earlier this year....

Some of us who have been here a bit longer than others may be well aware that an apparently correctly set Plusnet profile, when being applied, will always reduce your speed by a small but noticeable amount compared to exactly the same connection without the Plusnet profile being applied.

For reference:

https://community.plus.net/t5/Plusnet-Feedback/Affect-on-speeds-of-the-Plusnet-profile/td-p/991521

http://forums.thinkbroadband.com/plusnet/4428998-pn-ip-profile-and-bt-ip-profile.html

So I'd expect a static IP will always slightly reduce the throughput due to the effect of the Plusnet profile. It's all ancient history and no longer an issue for most customers, who are not on static IPs, and so the Plusnet profile is not applied to their connection.

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So despite having a full speed Sync, my Plusnet current line speed is only 73.8Mb!

[#11]

This is definitely a Profile issue, the reply from @TheMightyAJ is not at all helpful or correct. If the line is syncing at full speed, the line quality is obviously good. It can't be any better than that.

I queried this low IP profile problem recently see post 20 of this thread ...

https://community.plus.net/t5/Everything-else/Monitoring-Throughput/m-p/1694371#M22933 

the response was not clear, there is something going on with the BT wholesale IP profile calculation using a reduced sync speed value when the line is running on retransmission high which is one of the G.Inp operating states for longer lines where there may be more errors detected. . Although I have no errors showing my line is in this state and my IP profile is about 88% of the sync speed, then the PlusNet profile may or may not knock this down a bit more possibly depending on whether you have a static IP. I was not on a static IP and only got a throughput speed of about 65Mbps with a full 79.999Mbps sync speed which is not good.

I have just gone to a static IP and will see if anything changes, I feel I am losing a lot of potential speed because of the profile system.☹️ 

[#12]

Thanks for getting back to us @ncd

We've retested your line and there are no profiles on our end nor our suppliers that would be causing this.

I'm happy to try removing your static IP to see if that gives you an increase but due to you having a block of static IP's I can't gurantee that you'd get these back and they'd be most likely a different range

[#13]

@Kevin @RealAleMadrid thanks for both of your replies.
Did you ever get it sorted as it sounds like a well known issue?

[#14]

@MatthewWheeler thanks for the reply and kind offer but I'm not happy moving to a dynamic ip.

It sounds like this is a well known issue as several other people have reported they are affected both in this thread and other threads they have linked to.

What can we do to get this investigated further?

Thanks again!

[#15]

@ncd I keep wondering if I really need a static IP. Think I've had it since I joined the original fttc trial.

I'm about 300 odd metres from my cabinet, so although I sync at the max 80Mb, I doubt I will reach the theoretical max.

One day I'll have it taken off, just to see how much speed I actually gain. Probably only another couple of Mb's!

The only streaming problems I have is SkyGo, and that is more down to their rubbish player. Netflix, Iplayer (and the other channels players) and Amazon Prime all work fine.

So it's only bragging rights really!