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Broadband Related => Broadband Technology => Topic started by: GigabitEthernet on July 20, 2022, 02:58:43 PM

Title: FTTP questions
Post by: GigabitEthernet on July 20, 2022, 02:58:43 PM
Hi all,

FTTP has been ordered now we've got it in my area - I'm very excited (how's that for sad!).

I had a few curious questions.

The 900Mb package, is the maximum achievable speed 1000Mbps? As far as I understand it 1 Gb ethernet port can't actually achieve 1Gb, it's 940Mb, is this right? Is the Ethernet port out of the ONT 1Gb or is it 10Gb?

What is the maximum achievable upload speed?

Thanks.
Title: Re: FTTP questions
Post by: burakkucat on July 20, 2022, 05:42:59 PM
The 900Mb package, is the maximum achievable speed 1000Mbps? As far as I understand it 1 Gb ethernet port can't actually achieve 1Gb, it's 940Mb, is this right? Is the Ethernet port out of the ONT 1Gb or is it 10Gb?

A circuit provided over the Openreach GPON infrastructure can transfer bits at a maximum rate of 1 Gbps. However that bit stream includes all the overheads that are required to transfer Ethernet frames between an ISP and the end user. Hence the end user will not see 1 Gbps when performing a "speed test" (whatever that may be) but something in the region of 940 Mbps. Therefore you will typically find that ISPs will sell such a service as 900 Mbps.

Which service provider have you chosen?
Title: Re: FTTP questions
Post by: gt94sss2 on July 20, 2022, 05:52:41 PM
The Openreach ONTs are 1Gps and would need to be swapped to support higher speeds
Title: Re: FTTP questions
Post by: GigabitEthernet on July 20, 2022, 06:44:33 PM
A circuit provided over the Openreach GPON infrastructure can transfer bits at a maximum rate of 1 Gbps. However that bit stream includes all the overheads that are required to transfer Ethernet frames between an ISP and the end user. Hence the end user will not see 1 Gbps when performing a "speed test" (whatever that may be) but something in the region of 940 Mbps. Therefore you will typically find that ISPs will sell such a service as 900 Mbps.

Which service provider have you chosen?

TalkTalk.
Title: Re: FTTP questions
Post by: gt94sss2 on July 20, 2022, 07:30:00 PM
Talktalk are offering you a 900Mbps service?

As you know, I am on the same exchange as you but am only offered their Fibre 35 and Fibre 65 products..
Title: Re: FTTP questions
Post by: GigabitEthernet on July 20, 2022, 08:57:30 PM
Talktalk are offering you a 900Mbps service?

As you know, I am on the same exchange as you but am only offered their Fibre 35 and Fibre 65 products..

Yes although I only chose to go for 500 this time. Install is scheduled for the 8th August
Title: Re: FTTP questions
Post by: gt94sss2 on July 20, 2022, 09:31:18 PM
Yes although I only chose to go for 500 this time. Install is scheduled for the 8th August

Odd.. their checker doesn't seem to recognise the postcodes near me as being FTTP enabled. I wonder why.

The lines would be going to the same handover exchange so Talktalk would have connectivity there..
Title: Re: FTTP questions
Post by: GigabitEthernet on July 21, 2022, 09:24:30 AM
So if the ONT is 1Gbit and the Ethernet port coming out of it is 1Gbit, as far as I understand it's impossible to achieve 1 Gbit as in my experience over 1 Gbit Ethernet you can't achieve 1 Gbit?
Title: Re: FTTP questions
Post by: meritez on July 21, 2022, 10:14:50 AM
Odd.. their checker doesn't seem to recognise the postcodes near me as being FTTP enabled. I wonder why.

The lines would be going to the same handover exchange so Talktalk would have connectivity there..

what does https://bidb.uk/ show?
Title: Re: FTTP questions
Post by: RealAleMadrid on July 21, 2022, 10:56:05 AM
@GigabitEthernet Looks like you are agreeing with yourself, as you stated in your opening post you can't get 1Gbit/sec over a 1Gbit Ethernet connection. :o
Title: Re: FTTP questions
Post by: GigabitEthernet on July 21, 2022, 11:21:40 AM
@GigabitEthernet Looks like you are agreeing with yourself, as you stated in your opening post you can't get 1Gbit/sec over a 1Gbit Ethernet connection. :o

I am sorry I wasn't clear.

What I mean is, I know the GPON is at 1 Gb but am I right in saying it's impossible under any scenario to actually achieve 1 Gb because of Ethernet limitations?
Title: Re: FTTP questions
Post by: gt94sss2 on July 21, 2022, 12:18:22 PM
what does https://bidb.uk/ show?

That Openreach FTTP is live.. has been for about a month now. This seems like a Talktalk issue - it doesn't occur with other ISPs
Title: Re: FTTP questions
Post by: meritez on July 21, 2022, 03:15:54 PM
That Openreach FTTP is live.. has been for about a month now. This seems like a Talktalk issue - it doesn't occur with other ISPs

Yes, takes TalkTalk about 40 days to get their backhaul in place at the exchange...
Title: Re: FTTP questions
Post by: GigabitEthernet on July 21, 2022, 03:28:52 PM
Yes, takes TalkTalk about 40 days to get their backhaul in place at the exchange...

I'm on the same exchange and just ordered 500 yesterday. It's Wandsworth, I'm sure they already have the backhaul.
Title: Re: FTTP questions
Post by: burakkucat on July 21, 2022, 04:28:20 PM
What I mean is, I know the GPON is at 1 Gb but am I right in saying it's impossible under any scenario to actually achieve 1 Gb because of Ethernet limitations?

Yes. (Though I would not use the word "limitations".)

The best way to think of an ONT is as a media convertor from optical to electrical / from electrical to optical, along with electronics to perform the protocol transformation.
Title: Re: FTTP questions
Post by: Alex Atkin UK on July 21, 2022, 08:56:09 PM
I am sorry I wasn't clear.

What I mean is, I know the GPON is at 1 Gb but am I right in saying it's impossible under any scenario to actually achieve 1 Gb because of Ethernet limitations?

Well technically the GPON is at 2.4Gbit but your account profile will be somewhere around a Gigabit to prevent packet loss.  Ultimately you ARE getting Gigabit, if you're measuring the line-rate.  ISPs however are required to advertise real-world throughput after overheads, so they sell as 900Mbit.

I top out at 915Mbit which seems about right given I can only push 940Mbit over a Gigabit port on the LAN and then you have PPP overheads, plus whatever is happening from the ONT onwards (though I don't know what speed is provisioned there).
I can only assume people getting 940Mbit must be on an ISP using DHCP rather than PPP.

There's nothing technically to stop Openreach using higher-end ONTs that allow the full 2.4Gbit, other than it not being very sensible to allow one customer to max out the PON.

Some of the alt-nets let you do this (if you order something like 10Gbit symmetrical) which is why their performance will vary a lot more.
Title: Re: FTTP questions
Post by: Ixel on July 22, 2022, 08:46:36 PM
I can only assume people getting 940Mbit must be on an ISP using DHCP rather than PPP.

Most likely.

I'm connected via DHCP instead of PPPoE and if I'm connected to the ONT using a 1GbE RJ45 port on my router I get the following result:
(https://www.speedtest.net/result/13441906126.png)

When I was connected to the ONT using a 10GbE RJ45 port on my router I see a slight improvement resulting in getting pretty much spot on the maximum speed my current package is limited to:
(https://www.speedtest.net/result/13392981051.png)

Someone might be wondering why I'm not still connected using a 10GbE RJ45 port. That's because I'm reluctant to do so in case the problem I was recently having returns again due to that. If it's working fine then I feel it's best to leave it alone, at least for now. :D

Title: Re: FTTP questions
Post by: GigabitEthernet on July 22, 2022, 09:44:10 PM
Most likely.

I'm connected via DHCP instead of PPPoE and if I'm connected to the ONT using a 1GbE RJ45 port on my router I get the following result:
(https://www.speedtest.net/result/13441906126.png)

When I was connected to the ONT using a 10GbE RJ45 port on my router I see a slight improvement resulting in getting pretty much spot on the maximum speed my current package is limited to:
(https://www.speedtest.net/result/13392981051.png)

Someone might be wondering why I'm not still connected using a 10GbE RJ45 port. That's because I'm reluctant to do so in case the problem I was recently having returns again due to that. If it's working fine then I feel it's best to leave it alone, at least for now. :D



I don't get it, isn't the ONT port only 1 Gb? How is using 10 Gb going to make a difference, won't it just connect at 1 Gb any way?
Title: Re: FTTP questions
Post by: Ixel on July 22, 2022, 11:06:35 PM
I don't get it, isn't the ONT port only 1 Gb? How is using 10 Gb going to make a difference, won't it just connect at 1 Gb any way?

Depends on the ONT the network supplies. Openreach's ONTs only have one or more 1 GbE ports to my knowledge. Lightning Fibre's ONT however has both a 10 GbE port (which they use) and a 1 GbE port (seems to do nothing). As for Lightning Fibre, at the moment it doesn't make a significant difference but it will when they release packages which offer speeds greater than 1 gigabit.

At the moment if I connected using the 10 GbE port on my router and the 10 GbE port on the ONT then I'm able to reach almost exactly 1000 megabits with overheads. If I swap to a 1 GbE port on my router then it will be somewhere around 940 megabits instead (for IPoE, a little less for PPPoE). For now that's the only minor difference.

EDIT: Changed DHCP to say IPoE due to a subsequent 'pedant' reply. Not sure what they mean by PPP+PPPoE though.
Title: Re: FTTP questions
Post by: GigabitEthernet on July 22, 2022, 11:18:45 PM
Depends on the ONT the network supplies. Openreach's ONTs only have one or more 1 GbE ports to my knowledge. Lightning Fibre's ONT however has both a 10 GbE port (which they use) and a 1 GbE port (seems to do nothing). As for Lightning Fibre, at the moment it doesn't make a significant difference but it will when they release packages which offer speeds greater than 1 gigabit.

At the moment if I connected using the 10 GbE port on my router and the 10 GbE port on the ONT then I'm able to reach almost exactly 1000 megabits with overheads. If I swap to a 1 GbE port on my router then it will be somewhere around 940 megabits instead (for DHCP, a little less for PPPoE). For now that's the only minor difference.

Aha I see now. So I should be able to achieve around what you posted first as TalkTalk use DHCP
Title: Re: FTTP questions
Post by: Weaver on July 23, 2022, 02:07:32 AM
[Pedant_mode on] :-) As you know, you shouldn’t say ‘dhcp". You also know that DHCP is nothing to do with anything, it’s just a zeroconfig protocol, not a communications protocol. It’s not comparable with PPP, apart from in the sense which you know about, that most users who use ISP-DHCP remotely don’t use PPP. You should say "does not use PPP"  rather than "uses DHCP".[/Pedant_mode] :-)

Do you really think PPP makes any difference to speed ? It’s only two bytes. Or do you mean PPP+PPPoE over the internet access link?

A point occurs to me, if your system uses PPPoE over links further upstream than your router maybe the PPPoE headers are stripped so that means dropping 8 bytes of overhead. So even for a max len IP PDU that 8 bytes is what 0.53% speed difference, or if we drop PPP+PPPoE+MAC then that would be 8+22=30 bytes = 2%. Doesn’t seem very likely, but who knows.
Title: Re: FTTP questions
Post by: Alex Atkin UK on July 23, 2022, 02:11:01 AM
I've seen you mention this before and I'm lost at what you mean by PPP+PPPoE.
Title: Re: FTTP questions
Post by: Bowdon on July 23, 2022, 11:36:04 AM
Wouldn't it be possible to reach 1gig if you was able to use 2 ports, or 1 port and a wifi connection and somehow use a program on the computer to combine the download speed?

Though this would assume that 1gig is getting served to the router.
Title: Re: FTTP questions
Post by: Alex Atkin UK on July 23, 2022, 12:42:39 PM
Like you said, not unless this was two ports from the ONT to the router.
Title: Re: FTTP questions
Post by: GigabitEthernet on July 23, 2022, 02:09:42 PM
Wouldn't it be possible to reach 1gig if you was able to use 2 ports, or 1 port and a wifi connection and somehow use a program on the computer to combine the download speed?

Though this would assume that 1gig is getting served to the router.

So I guess this comes back to my original question.

If the ONT is connected/limited at 1 Gb and the port is connected at 1 Gb, is it actually possible in any scenario for the router to actually achieve 1 Gb?

I thought something with jumbo frames made throughput higher
Title: Re: FTTP questions
Post by: Weaver on July 23, 2022, 03:30:41 PM
Alex, as you know, since PPPoE is always found in the midst of a trio of protocols: PPP, PPPoE and then ethernet or the ethernet MAC (sub)layer, people do confuse the PPPoE protocol alone with the entire group of all three as a unit. Strangely, the ethernet MAC header is in fact sometimes found in use with PPPoE headers even when the ethernet protocol is not in use, not physically present on an ethernet network. This seems to serve no purpose apart from adding further unnecessary header overhead, so-called bloat.

One case where it is important to disambiguate: PPP has an overhead of 2 bytes; PPPoE has an overhead of 6 bytes, so PPP+PPPoE overhead is 8 bytes which is the overhead incurred when having a PPP+PPPoE connection from a router to a modem over ethernet, eg think of the well known case of PPP MTU = 1500 + (2 + 6) = 1508 bytes.
Title: Re: FTTP questions
Post by: Alex Atkin UK on July 24, 2022, 05:41:07 PM
I still don't understand what you mean by a PPP+PPPoE connection.  Where is this first PPP coming into the equation?

Its confusing enough that L2TP is also based on PPP to the point pfSense bundle it into the PPP section in the UI. (so that could technically be PPP+PPPoE if I ran it over my Zen connection, but its not, as its running over Three 5G)

I can't figure in what scenario you would run over PPP twice, unless further up the chain L2TP is being used.
Title: Re: FTTP questions
Post by: Weaver on July 25, 2022, 10:45:58 AM
PPP is a separate protocol that predates PPPoE. The PPP header is 2 bytes and the PPPoE header is 6 bytes. It’s entirely possible to have PPP on its own, without PPPoE. You can use PPP alone in the case of dial-up using an old fashioned dial-up modem, and that’s exactly what we did before ADSL became available. And it’s what I did for 8 years before 2004 to get internet access.

So when I say PPP+PPPoE that means I’m talking about the sum of the two headers, 2+6 = 8 bytes. If I talk about PPPoE, depending on context, I can talk about the 6 byte header alone, but this is infrequent, and that may be confusing for you. And it’s not helpful on my part unless we’re talking about headers rather than protocols and protocol stacks.

In the case of a Draytek Vigor 130, where we’re using ADSL G.992.1 and PPPoA, the modem acts as a protocol converter: it speaks PPPoEoE (the trio of protocols) on the LAN side and PPP+PPPoA+AAL5+ATM+DSL on the DSL side. So that’s an example where PPPoE is only used to talk to a modem from a router and no further upstream.
Title: Re: FTTP questions
Post by: GigabitEthernet on July 25, 2022, 02:31:14 PM
So what’s the most that is actually possible to achieve on 1Gb Openreach FTTP? Is it a fixed 940?
Title: Re: FTTP questions
Post by: Weaver on July 25, 2022, 04:46:04 PM
To be strictly accurate you have to say how much of what it is you’re sending. I would go for IP PDUs; which means that you count and include the IP headers themselves and everything else. You need to say whether you mean IPv4 or IPv6.  If using TCP then you also have to include IP and TCP headers, and say whether you’re including TCP timestamps on or off, and then there is the slowness associated with the TCP protocol itself; when a packet is dropped, TCP slows down and takes some time to recover to full speed if the system is less than ideal. A good setup will work out the bottleneck link speed and keep close to that rather than overloading the link then backing off and cycling giving a sawtooth-shaped speed vs time graph on a detailed speed checker. That overhead is difficult to estimate as it depends on the TCP implementations in use at both ends, the kind of path through the internet, time delays, and the amounts of buffering at the end-nodes and intermediate modes.

The 940 Mbps thing might have come from a TCP payload-only figure as reported by some speed tester. But if it is counting TCP payload only, then the true link performance is rather greater because the overheads of IP+TCP headers have been forgotten, as well as not accounting for the slowness of say the TCP protocol itself. They probably think that TCP payload is how the ‘man in the street’ thinks of ’speed’. Using a UDP-based carefully designed link performance measuring tool is the right way to measure the link, not the software. It would be interesting to try iperf3.

Actually you could argue that one should add in the overhead of ethernet headers too, if the FTTP service is delivering ethernet not IPv4 and IPv6 alone.
Title: Re: FTTP questions
Post by: burakkucat on July 25, 2022, 05:47:58 PM
So what’s the most that is actually possible to achieve on 1Gb Openreach FTTP? Is it a fixed 940?

In one word: Yes.

In two words: There about.
Title: Re: FTTP questions
Post by: GigabitEthernet on July 25, 2022, 08:24:29 PM
In one word: Yes.

In two words: There about.

Thanks a lot.