On 3/24/23 15:23, Diana Eichert wrote:
> GPON 30000 foot level from someone who has been apart of large
> enterprise GPON installation for ~ 15 years.
>
> GPON is transport, not ethernet, think SONET or DWDM or any other
> myriad transport layers.
>
> GPON OLT ( Optical Line Terminal ) looks like a switch but it isn't,
> in the Telco world it is called "shelf"
> OLT is connected upstream to ethernet backbone; ex: direct ethernet or
> via DWDM. Today this upstream is probably 100G, in the past it was
> 10G or 1G.
> OLT has PON ports, our legacy install has 4 PON ports per blade and 8
> blades per shelf.
> PON has single fiber ( with different Tx and Rx lambda ) which
> connects to a splitter ( anywhere from 16:1 to 64:1 )
> The output of the splitter goes to an ONT ( Optical Network Terminal
> ), depending on the ONT it can have 1 to n ethernet ports,
> 100Mb/1Gb/10Gb.
>
> The downstream (Tx) is sent to everyone, hopefully it is encrypted,
> however that is an OLT configuration. Encryption did not used to be
> enabled by default, we learned that in our initial installation when
> the evil twin in our enterprise said they could see everything
> transmitted to the ONT.
> The upstream (Rx) is read via a timeslot ( think TDM ) allocated to each ONT.
>
> So if you have managed to keep reading up to this point you will see
> there is over subscription all through this system. From the upstream
> connection, you have some number of PON ports/blade, then some number
> of blades/OLT, add in the passive splitters and then the number of
> ethernet ports on the ONT.
>
> So, just because your system ( router/computer ) connects at some
> speed you will never sustain anywhere near what your local connection
> speed.
>
> I hope I haven't bored to many people.
>
> diana
> KI5PGJ
>
This is really interesting! Thank you Diana.... you sound very much like
the very nice tech support team member that I just got off the phone
with. I really wish I had proper ISP experience in me rather then end
user type now, it sounds like a lot of fun and a great learning
experience.... back in the day it was everything I studied for but too
many road blocks in the middle with my health being the worst :-(
I was thinking based on what Stuart wrote previously that the upstream
will use some form of Time Division Multiplexing and you have just
confirmed that :-)
The ONT that I will receive will have a single Ethernet port so line
rate speeds will be capped to 1Gb/s
I'm just responding to Stuarts other mail right now with more details of
the current conversation that has transpired a few minutes ago ;-)
Kaya
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