On Wednesday, 12 August 2020 10:14:05 UTC+1, The Natural Philosopher wrote:
On 12/08/2020 07:55, Andy Burns wrote:
The Natural Philosopher wrote:

no.
Not according to what wiki says. Its all wavelength division.

So the openreach chappie keeps 32 "flavours" of ONT on his van to cope
with different lambdas does he?

In the same way that a single radio tuner can receive the whole VHF
band, no.

Scan all frequencies till the one that is transmitting your MAC, or
whatever, is found..

In case anyone is interested, this is all defined in ITU-T G.984.3
which can be downloaded free of charge from various sites.

Section 5.5 of that document has the title:

"G-PON time division multiplexing architecture"

The way in which uplink data frames are allocated transmission times,
including compensation for varying propagation delay in the fibre with
distance to avoid collisions is all defined.
The BT residential service only uses wavelength division to separate
the uplink from the downlink on a single fibre.

John

On 12/08/2020 08:41, Dave Liquorice wrote:
On Wed, 12 Aug 2020 07:44:31 +0100, The Natural Philosopher wrote:

The kind of fibre service that BT are offering is unfortunately
not
at all symmetric.ÂÂ* The uplink is time division multiplexed in
the
same sort of way that cable services operate.

I dont think so.
No on uses TDM these days - its all packet switched

He's right ...

Everyone is sharing a single fibre at the exchange-end, one
downstream
wavelength gives 2.48 Mbps, a different wavelength gives 1.24 Mbps

upstream, closer to the premises it gets passively optically split
for
up to 32 sub-fibres to the premises.

Or even up to 64 but that starts to limit the range to less than 10
km on a subs fibre. B-)

All downstream packets arrive at all premises and the ONT filters
out
everyone's but yours, there are timeslots that you get to transmit
on
the upstream wavelength to fit your traffic around everyone
else's.

no.
Not according to what wiki says. Its all wavelength division.

Wavelength for the up/down combined streams.
Time for individual connections within those streams.

Are we also being sold a pup again with "1 Gbps capable" connections?
If the down stream is limited to 2.48 G bps and all 32 customers are
trying to fill their pipe surely all they'll get is 2.48/32 ~ 78 Mbps
throughput even if individual packets are signalled at 2.48 Gbps.


ISTM BT are no different from VM in promising (maximum) /speed/ rather
than absence of /contention/ - though ISTR BT were looking to upgrade
the down from 2.5 to 10 using newer kit on newer installations.

Still a matter of business products if you want freedom from contention?

--
Robin
reply-to address is (intended to be) valid

On 12/08/2020 13:58, Robin wrote:
ISTM BT are no different from VM in promising (maximum) /speed/ rather
than absence of /contention/ - though ISTR BT were looking to upgrade
the down from 2.5 to 10 using newer kit on newer installations.

Still a matter of business products if you want freedom from contention?

Contention is meaningless except in a packet switched context.
If it IS time division or frequency division multiplexed, there *is* no
contention. The guaranteed subscriber time/frequency slots exist
whether full of data, or empty.

No matter which technology is used, the 'last mile' is not contended..
It's the backhaul that is.



--
Ideas are more powerful than guns. We would not let our enemies have
guns, why should we let them have ideas?

Josef Stalin

On Monday, 10 August 2020 17:19:19 UTC+1, Andrew wrote:

I have 26 Mbps from BT FTTC and have never used more than 10Giga in a
month.
What on earth DO people do with such massive speeds ?.

We've got a 60 Mbps FTTC connection and according to the router we downloaded 621 GB last month! Whilst we stream all our TV, and download quite a few films (and F1 races), I must admit I didn't think it was going to be that high.

On 10/08/2020 17:19, Andrew wrote:
On 10/08/2020 11:19, Andy Burns wrote:
Dave Liquorice wrote:

I can't see them managing to complete the "full fibre" network by
2025.

Is that still the target timescale?

https://www.bbc.co.uk/news/technology-50042720

Why the hang-up with gigabit speeds?

https://researchbriefings.files.parliament.uk/documents/CBP-8392/CBP-8392.pdf


I have ~75 Mbps from a BT cabinet that I can *just* see if I lean out
of the window.Â* Alternatively I could have up to 500 Mbps from virgin
FTTP where they have what is apparently called a "toby" in the
footpath at the end of my drive, same as this ...

https://www.chatteris.biz/blog/wp-content/uploads/2018/02/IMG_2286-Medium.jpg


I have 26 Mbps from BT FTTC and have never used more than 10Giga in a
month.


Well according to my stats:

"During the time period 1st August 2020 to 12th August 2020 your
bandwidth use was:

238.25 GB Download
8.2 GB Upload

The figures above cover 11 days."

The quantity of data will be influenced by the speed though.


What on earth DO people do with such massive speeds ?.

Slightly different issue. Much depends on what you do... Here it would
be quite common to have three video streams running at once, and since
the link is capable that would aauto adjust to three high def streams.

If you are a content producer, then having "only" 30Mbps upload speed
could actually be quite limiting. Same can apply for things like online
backup or cloud storage.




--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
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On 12/08/2020 22:07, Mathew Newton wrote:
On Monday, 10 August 2020 17:19:19 UTC+1, Andrew wrote:

I have 26 Mbps from BT FTTC and have never used more than 10Giga in a
month.
What on earth DO people do with such massive speeds ?.

We've got a 60 Mbps FTTC connection and according to the router we downloaded 621 GB last month! Whilst we stream all our TV, and download quite a few films (and F1 races), I must admit I didn't think it was going to be that high.

Wow. I am only managing about 60GB down and 40GB up... (up is high
because friends and family watch videos on my server)

--
In a Time of Universal Deceit, Telling the Truth Is a Revolutionary Act.

- George Orwell