The download speed on my Zen FTTC "unlimited fibre 1" has started
slowing down, particularly during the recent hot afternoons. Upload is
not effected. The noise margins look to still be good over 11dB on
download and about 7.5dB on upload.
I've tried different modems (a couple of HG612 and a MT992) and that
makes no difference. I think I am connected to a Huawei cabinet.
Is this a known fault with Huawei cabinets?
What are my chances of getting Zen to do anything about it?

--
Brian Gregory (in England).

Brian Gregory <void-invalid-dead-dontuse@email.invalid> wrote:
> The download speed on my Zen FTTC "unlimited fibre 1" has started
> slowing down, particularly during the recent hot afternoons. Upload is
> not effected. The noise margins look to still be good over 11dB on
> download and about 7.5dB on upload.

What is 'slow' and what is 'normal'?

> I've tried different modems (a couple of HG612 and a MT992) and that
> makes no difference. I think I am connected to a Huawei cabinet.
> Is this a known fault with Huawei cabinets?

I've seen my VDSL link go wibbly-wobbly, all kinds of speeds down from 76Mbps
to 50/40/30/20/10/5Mbps. No apparent cause, but it sorted itself out
eventually.

(it seemed my Sky SR203's Broadcom-based modem was better at handling it
than the Lantiq-based Homehub5a)

> What are my chances of getting Zen to do anything about it?

I think there is a guaranteed minimum speed on each VDSL contract - are you
below that? I think it would need to stay there for a while before you can
make a claim though.

Theo

Brian Gregory <void-invalid-dead-dontuse@email.invalid> wrote:
> slowing down, particularly during the recent hot afternoons. Upload is
> not effected. The noise margins look to still be good over 11dB on

Or aven affected....

--
Chris Green
·

On 16/06/2023 19:51, Chris Green wrote:
> Brian Gregory <void-invalid-dead-dontuse@email.invalid> wrote:
>> slowing down, particularly during the recent hot afternoons. Upload is
>> not effected. The noise margins look to still be good over 11dB on
>
> Or aven affected....
>

Oops :)

--
Brian Gregory (in England).

On 16/06/2023 19:24, Theo wrote:
> I've seen my VDSL link go wibbly-wobbly, all kinds of speeds down from 76Mbps
> to 50/40/30/20/10/5Mbps. No apparent cause, but it sorted itself out
> eventually.

Were you able to do any diagnostics?

Mine returns pretty much to normal once the sun starts to go down.

--
Brian Gregory (in England).

On 16/06/2023 at 18:34, Brian Gregory wrote:
> The download speed on my Zen FTTC "unlimited fibre 1" has started
> slowing down, particularly during the recent hot afternoons. Upload is
> not effected. The noise margins look to still be good over 11dB on
> download and about 7.5dB on upload.
> I've tried different modems (a couple of HG612 and a MT992) and that
> makes no difference. I think I am connected to a Huawei cabinet.
> Is this a known fault with Huawei cabinets?
> What are my chances of getting Zen to do anything about it?
>

This seems to be normal behaviour. I keep a log of connection speeds
for my BT Broadband VDSL Fibre 2 service and the hotter the weather, the
slower the connection speed noted over the past 3 or 4 years. I assume
that's because the resistance in joints in the copper wires leading from
the cabinet (about 0,75km away) gets higher the warmer it becomes (as
per elementary physics).

--
Wilf

On 17/06/2023 13:20, Wilf wrote:
> On 16/06/2023 at 18:34, Brian Gregory wrote:
>> The download speed on my Zen FTTC "unlimited fibre 1" has started
>> slowing down, particularly during the recent hot afternoons. Upload is
>> not effected. The noise margins look to still be good over 11dB on
>> download and about 7.5dB on upload.
>> I've tried different modems (a couple of HG612 and a MT992) and that
>> makes no difference. I think I am connected to a Huawei cabinet.
>> Is this a known fault with Huawei cabinets?
>> What are my chances of getting Zen to do anything about it?
>>
>
> This seems to be normal behaviour.  I keep a log of connection speeds
> for my BT Broadband VDSL Fibre 2 service and the hotter the weather, the
> slower the connection speed noted over the past 3 or 4 years.  I assume
> that's because the resistance in joints in the copper wires leading from
> the cabinet (about 0,75km away) gets higher the warmer it becomes (as
> per elementary physics).
>

I don't think this is what's happening to me. My noise margins remain
excellent, so it's nothing to do with the line. The modem still says
it's synced at the full speed of my connection.

I'm talking about major drop in speed.
I was down to little more than a tenth my normal speed at the end of the
hottest afternoon this week.

Does that match your experience?

--
Brian Gregory (in England).

On 17/06/2023 at 16:54, Brian Gregory wrote:
> On 17/06/2023 13:20, Wilf wrote:
>> On 16/06/2023 at 18:34, Brian Gregory wrote:
>>> The download speed on my Zen FTTC "unlimited fibre 1" has started
>>> slowing down, particularly during the recent hot afternoons. Upload is
>>> not effected. The noise margins look to still be good over 11dB on
>>> download and about 7.5dB on upload.
>>> I've tried different modems (a couple of HG612 and a MT992) and that
>>> makes no difference. I think I am connected to a Huawei cabinet.
>>> Is this a known fault with Huawei cabinets?
>>> What are my chances of getting Zen to do anything about it?
>>>
>>
>> This seems to be normal behaviour.  I keep a log of connection speeds
>> for my BT Broadband VDSL Fibre 2 service and the hotter the weather, the
>> slower the connection speed noted over the past 3 or 4 years.  I assume
>> that's because the resistance in joints in the copper wires leading from
>> the cabinet (about 0,75km away) gets higher the warmer it becomes (as
>> per elementary physics).
>>
>
> I don't think this is what's happening to me. My noise margins remain
> excellent, so it's nothing to do with the line. The modem still says
> it's synced at the full speed of my connection.
>
> I'm talking about major drop in speed.
> I was down to little more than a tenth my normal speed at the end of the
> hottest afternoon this week.
>
> Does that match your experience?
>

No. My downstream connection speed has tended to vary over the months
from around 73Mb/s in cold weather down to around 66Mb/s in hot weather.
Of course I don't experience those speeds in reality - those are the
purported connection speeds. I tend to actually get in terms of a speed
test, around 10Mb/s less than those connection speeds. So 55-59 or so
in hot weather, 60-64 in cold weather.

--
Wilf

On Fri, 16 Jun 2023 18:34:53 +0100
Brian Gregory <void-invalid-dead-dontuse@email.invalid> wrote:

> The download speed on my Zen FTTC "unlimited fibre 1" has started
> slowing down, particularly during the recent hot afternoons. Upload
> is not effected. The noise margins look to still be good over 11dB on
> download and about 7.5dB on upload.
> I've tried different modems (a couple of HG612 and a MT992) and that
> makes no difference. I think I am connected to a Huawei cabinet.
> Is this a known fault with Huawei cabinets?
> What are my chances of getting Zen to do anything about it?
>

Ask them. They have a good reputation for getting OR to do things, so
it can't do any harm to ask.

--
Davey.

On 17/06/2023 18:11, Davey wrote:
> On Fri, 16 Jun 2023 18:34:53 +0100
> Brian Gregory <void-invalid-dead-dontuse@email.invalid> wrote:
>
>> The download speed on my Zen FTTC "unlimited fibre 1" has started
>> slowing down, particularly during the recent hot afternoons. Upload
>> is not effected. The noise margins look to still be good over 11dB on
>> download and about 7.5dB on upload.
>> I've tried different modems (a couple of HG612 and a MT992) and that
>> makes no difference. I think I am connected to a Huawei cabinet.
>> Is this a known fault with Huawei cabinets?
>> What are my chances of getting Zen to do anything about it?
>>
>
> Ask them. They have a good reputation for getting OR to do things, so
> it can't do any harm to ask.
>

I'm waiting for a response from them.

--
Brian Gregory (in England).

Brian Gregory wrote:
> On 17/06/2023 13:20, Wilf wrote:
>> On 16/06/2023 at 18:34, Brian Gregory wrote:
>>> The download speed on my Zen FTTC "unlimited fibre 1" has started
>>> slowing down, particularly during the recent hot afternoons. Upload is
>>> not effected. The noise margins look to still be good over 11dB on
>>> download and about 7.5dB on upload.
>>> I've tried different modems (a couple of HG612 and a MT992) and that
>>> makes no difference. I think I am connected to a Huawei cabinet.
>>> Is this a known fault with Huawei cabinets?
>>> What are my chances of getting Zen to do anything about it?
>>>
>>
>> This seems to be normal behaviour.  I keep a log of connection speeds
>> for my BT Broadband VDSL Fibre 2 service and the hotter the weather,
>> the slower the connection speed noted over the past 3 or 4 years.  I
>> assume that's because the resistance in joints in the copper wires
>> leading from the cabinet (about 0,75km away) gets higher the warmer it
>> becomes (as per elementary physics).
>>
>
> I don't think this is what's happening to me. My noise margins remain
> excellent, so it's nothing to do with the line. The modem still says
> it's synced at the full speed of my connection.
>
> I'm talking about major drop in speed.
> I was down to little more than a tenth my normal speed at the end of the
> hottest afternoon this week.
>
> Does that match your experience?
You should be careful to distinguish between the FTTC/VDSL sync speed as
reported by your router and the download rate as reported by a site such
as speedtest.net

The sync speed, SNR margin, and loop attenuation are all inter-related.
The sync speed is capped at either 40 Mbits/sec or 80 Mbits/sec
according to the service you have bought. If it is reported at either
of these, the SNR margin is fairly irrelevent and you will probably see
the loop attenuation is quite small. If the sync speed is less than the
capped value then ideally the SNR margin will tend to about 6dB.
Anything higher than that indicates that the line is not ideal - noisy
at some part of the spectrum, perhaps. A high value for loop
attenuation is consistent with a greater distance from the green cabinet.

Sync speed is affected by electrical noise - lightning, electric fences,
Chrismas tree lights, poor joints on the copper pair, water in the
underground ducts, etc. Zen will usually call out Openreach if your
sync speed suddenly changes. The only really good resolution is to
change to FTTP if the option is available to you.

The download rate is affected by congestion - other people making use of
the same backhaul from the green cabinet to the test website. This
depends very much on the local infrastructure. You will often see a
reduction in speed as the kiddies come home from school, though that is
now more noticeable on 3G/4G/5G connections since they are all using
their phones for internet connectivity.

--
Graham J

On 18/06/2023 08:42, Graham J wrote:
> Brian Gregory wrote:
>> On 17/06/2023 13:20, Wilf wrote:
>>> On 16/06/2023 at 18:34, Brian Gregory wrote:
>>>> The download speed on my Zen FTTC "unlimited fibre 1" has started
>>>> slowing down, particularly during the recent hot afternoons. Upload is
>>>> not effected. The noise margins look to still be good over 11dB on
>>>> download and about 7.5dB on upload.
>>>> I've tried different modems (a couple of HG612 and a MT992) and that
>>>> makes no difference. I think I am connected to a Huawei cabinet.
>>>> Is this a known fault with Huawei cabinets?
>>>> What are my chances of getting Zen to do anything about it?
>>>>
>>>
>>> This seems to be normal behaviour.  I keep a log of connection speeds
>>> for my BT Broadband VDSL Fibre 2 service and the hotter the weather,
>>> the slower the connection speed noted over the past 3 or 4 years.  I
>>> assume that's because the resistance in joints in the copper wires
>>> leading from the cabinet (about 0,75km away) gets higher the warmer
>>> it becomes (as per elementary physics).
>>>
>>
>> I don't think this is what's happening to me. My noise margins remain
>> excellent, so it's nothing to do with the line. The modem still says
>> it's synced at the full speed of my connection.
>>
>> I'm talking about major drop in speed.
>> I was down to little more than a tenth my normal speed at the end of
>> the hottest afternoon this week.
>>
>> Does that match your experience?
> You should be careful to distinguish between the FTTC/VDSL sync speed as
> reported by your router and the download rate as reported by a site such
> as speedtest.net
>
> The sync speed, SNR margin, and loop attenuation are all inter-related.
> The sync speed is capped at either 40 Mbits/sec or 80 Mbits/sec
> according to the service you have bought.  If it is reported at either
> of these, the SNR margin is fairly irrelevent and you will probably see
> the loop attenuation is quite small.  If the sync speed is less than the
> capped value then ideally the SNR margin will tend to about 6dB.
> Anything higher than that indicates that the line is not ideal - noisy
> at some part of the spectrum, perhaps.  A high value for loop
> attenuation is consistent with a greater distance from the green cabinet.
>
> Sync speed is affected by electrical noise - lightning, electric fences,
> Chrismas tree lights, poor joints on the copper pair, water in the
> underground ducts, etc.  Zen will usually call out Openreach if your
> sync speed suddenly changes.  The only really good resolution is to
> change to FTTP if the option is available to you.
>
> The download rate is affected by congestion - other people making use of
> the same backhaul from the green cabinet to the test website.  This
> depends very much on the local infrastructure.  You will often see a
> reduction in speed as the kiddies come home from school, though that is
> now more noticeable on 3G/4G/5G connections since they are all using
> their phones for internet connectivity.
>

All understood and agreed.

I am seeing sync speeds that, as is usual for me, match the 40 down, 10
up specification of my service. It's just the actual download data rate
on speed test and other websites that has been reducing during the
hottest afternoons.

If congestion is a common occurrence, doesn't that break VoIP for those
that have been switched over to VoIP for their telephone service?

--
Brian Gregory (in England).

Brian Gregory wrote:

[snip]

> All understood and agreed.
>
> I am seeing sync speeds that, as is usual for me, match the 40 down, 10
> up specification of my service. It's just the actual download data rate
> on speed test and other websites that has been reducing during the
> hottest afternoons.
>
> If congestion is a common occurrence, doesn't that break VoIP for those
> that have been switched over to VoIP for their telephone service?

Probably not. VoIP can work on a very slow connection - 100kbits sec
would probably be OK. What it can't tolerate is breaks such as occur
when a lightning strike causes your VDSL to re-synchronise.

Roll on FTTP !!!

--
Graham J

On 18/06/2023 21:54, Graham J wrote:
> Probably not.  VoIP can work on a very slow connection - 100kbits sec
> would probably be OK.  What it can't tolerate is breaks such as occur
> when a lightning strike causes your VDSL to re-synchronise.

Does you line come to you above ground on telegraph poles?

This is not an issue with underground lines and great noise margins like
on my connection.

The only way congestion can slow things is if packets are being dropped
when queues fill up.

Queues mean delay which disturbs VoIP.
Dropped packets disturb VoIP.

I'd love to know how this is handled in practice because I don't want to
be forced to use the ATA (or router) my ISP provides.

--
Brian Gregory (in England).

Graham J wrote:

> What it can't tolerate is breaks such as occur when a lightning strike
> causes your VDSL to re-synchronise.

my ADSL connection would never survive a lightning storm, but I don't
think it affects me since upgrading to VDSL several years ago, finally
was able to use the blitzortung website in real time ...

On 17/06/2023 20:57, Brian Gregory wrote:
> On 17/06/2023 18:11, Davey wrote:
>> On Fri, 16 Jun 2023 18:34:53 +0100
>> Brian Gregory <void-invalid-dead-dontuse@email.invalid> wrote:
>>
>>> The download speed on my Zen FTTC "unlimited fibre 1" has started
>>> slowing down, particularly during the recent hot afternoons. Upload
>>> is not effected. The noise margins look to still be good over 11dB on
>>> download and about 7.5dB on upload.
>>> I've tried different modems (a couple of HG612 and a MT992) and that
>>> makes no difference. I think I am connected to a Huawei cabinet.
>>> Is this a known fault with Huawei cabinets?
>>> What are my chances of getting Zen to do anything about it?
>>>
>>
>> Ask them. They have a good reputation for getting OR to do things, so
>> it can't do any harm to ask.
>>
>
> I'm waiting for a response from them.
>

I had the usual response suggesting a few checks I could do on my
equipment and I was waiting for a really hot afternoon to do dome
testing before replying.

But now, as of about lunch time today it looks like something somewhere
has been fixed and my connection is behaving itself at the moment. I'll
know for sure in a coupe of days.

--
Brian Gregory (in England).