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Author Topic: Understanding FTTP upstream  (Read 495 times)

Weaver

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Understanding FTTP upstream
« on: March 25, 2022, 08:30:50 AM »

I donít understand how upstream performance is determined in the various FTTP protocols - maybe someone could help me out? Iíd also like to understand how upstream speeds affect pricing.

I have noted various symmetric offerings: the very expensive dedicated link service from the likes of AA; the likes of B4RN which are symmetric, fantastically cheap ;D, shared and presumably heavily contended?; and NetOmnia about which I know nothing at all.

I assume that service providers donít want to just give everyone symmetric services because doing so would tempt business users to buy vastly cheaper residential/domestic services for no money? But Iím waiting to be told that it isnít remotely that simple, unless you are B4RN?
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burakkucat

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Re: Understanding FTTP upstream
« Reply #1 on: March 25, 2022, 02:39:50 PM »

. . . the likes of B4RN which are symmetric, fantastically cheap ;D, shared and presumably heavily contended?

Both B4RN (Lancashire) and B4SH (Surrey) are point to point fibres, with nothing shared nor contended.
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Reformed

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Re: Understanding FTTP upstream
« Reply #2 on: March 25, 2022, 03:21:12 PM »

Both B4RN (Lancashire) and B4SH (Surrey) are point to point fibres, with nothing shared nor contended.

Contended but neither visibly or between the laser on the operator's side and the one at the home.

licquorice

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Re: Understanding FTTP upstream
« Reply #3 on: March 25, 2022, 03:22:20 PM »

Hmm, nothing contended from the customer to the head end, but the backhaul will be contended.

Post crossed with @Reformed's post
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Reformed

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Re: Understanding FTTP upstream
« Reply #4 on: March 25, 2022, 03:27:34 PM »

I donít understand how upstream performance is determined in the various FTTP protocols - maybe someone could help me out? Iíd also like to understand how upstream speeds affect pricing.

Not much to say. As far as the UK goes on GPON it's 1.25G before overheads split between 30-32 premises passed, with 2.5G down. This is used by Openreach, CityFibre on their residential, and no doubt some others. Netomnia, Community Fibre and some others use XGSPON, 8.5G after overheads split between up to 64 premises passed.

The rest is capacity planning and commercial decisions. Openreach don't offer higher upstream because they want people to buy dedicated lines rather than broadband, and charge a heavy premium for minimal additional upstream speed, CityFibre tolerate a higher level of contention, some others have symmetrical access networks but will monitor usage to some extent as it is much easier to max out upstream 24x7 than down and basically none of those applications will be compliant with a reasonable acceptable use policy.

Weaver

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Re: Understanding FTTP upstream
« Reply #5 on: March 25, 2022, 10:23:02 PM »

Presumably your £900-per onto AA/BT dedicated line has no AUP? Is such a dedicated line something other than xPON?

@Burakkucat I think I used the wrong terminology there, no?
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Reformed

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Re: Understanding FTTP upstream
« Reply #6 on: March 26, 2022, 11:56:40 AM »

Correct. Usually 1000Base-BX or 10000Base-BX for leased / dedicated lines.

PON can emulate leased lines but in the UK that's not really done. People may and do advertise relatively low speed Ethernet services that are using FTTC/P but they do not come with the service level agreements private lines do.

Emulation of leased services over PON is done either by selling the service at the guaranteed minimum speed or by using QoS to assign higher priority to those customers on the PON so they get their upstream TDMA slots before regular customers and their downstream is prioritised for transmission.

burakkucat

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Re: Understanding FTTP upstream
« Reply #7 on: March 26, 2022, 04:07:19 PM »

@Burakkucat I think I used the wrong terminology there, no?

Sorry but I am unsure of what it is that you asking.
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Weaver

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Re: Understanding FTTP upstream
« Reply #8 on: March 26, 2022, 11:14:56 PM »

@Burakkucat I think I confused matters by using words such as Ďcontentioní inappropriately?
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AnthonyG

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Re: Understanding FTTP upstream
« Reply #9 on: March 27, 2022, 12:25:58 AM »

I assume that service providers donít want to just give everyone symmetric services because doing so would tempt business users to buy vastly cheaper residential/domestic services for no money? But Iím waiting to be told that it isnít remotely that simple, unless you are B4RN?

Cityfibre offer symmetrical through all of their supported ISPs. Even when you sign up to a contract saying 500mb down 75up. You seem to get 500mb/500mb (or as I have got 560mb/560mb).

And CityFibre charge considerably less than Openreach for this better service.
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burakkucat

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Re: Understanding FTTP upstream
« Reply #10 on: March 27, 2022, 11:58:43 PM »

@Burakkucat I think I confused matters by using words such as Ďcontentioní inappropriately?

Ah, I see. Both Reformed and licquorice have mentioned where there will be contention but I was thinking purely about the fibre between the optics. As, I suspect, were you.
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Reformed

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Re: Understanding FTTP upstream
« Reply #11 on: March 28, 2022, 12:36:35 AM »

Yus, the point to point stuff is exactly that. It has no more contention between premises and switch than a DSL service does between premises and DSLAM. This obviously also means there's no media acquisition or TDMA required as it's not shared.

The PON technologies as I think I mentioned on a thread where Weaver asked what 'N' was in an overheads document use TDMA and broadcast a MAP message periodically to all ONTs on the PON providing them a time they may transmit upstream and how many TDMA timeslots they have. These are very finely timed and each burst from an ONT has a preamble and postamble CRC to further protect against collisions.

http://jm.telecoms.free.fr/QCM_Fibre/GPON-Fundamentals_Huawei.pdf will I suspect be of interest. XGSPON is that with more bandwidth and more expensive upstream lasers basically.