[Cerowrt-devel] a smart SFP

Thu Jan 13 10:44:23 EST 2022

Hi Dave,

> On Jan 13, 2022, at 16:28, Dave Taht <dave.taht at gmail.com> wrote:
> 
> yes, well, I dislike intensely the implications of
> not-so-intelligently splitting those 128 terminals is, and was pleased
> to see there was support

	Nobody in their right mind is going to hook up 128 terminalt to one OLT port, I hope...

> at least, for hardware flow control on the uplink side in the spec.

	The spec, as many ITU documents contains probably more than anybody is going to use ;)
But GPON uses a request-grant system for upstream scheduling similar to DOCSIS (when looking at both from great height), just with a much faster message clock and hence less total and especially less variability in delay, if I understood things correctly.

> Since we've fixed dsl, cable, and wifi, getting gpon more right has
> increasingly
> been on my mind...

	Fist question might to be "how broken is GPON/XGPON" to start with, no?

> so pulling  a testbed together of some sort would
> be cool, and for that matter, having a SFP that could go right into a
> SFP enabled home router rather than a separate unit seems like a good
> idea, also.

	Meh, unless you actually get root on the ONU, it will basically act like a small media converter whether you connect via SFP or via ethernet. In Germany enthusiasts started to look at SFP-ONUs partly because ISPs were provisioning more GPON "rate" than required for that the ~940 Mbps goodput of gigabit ethernet, going SFP allowed some to run (compatible SFP-onus) at 2.5 Gbps link rate to the SFP cage hence allowing speedtest superiority... (that and to clone ONUs so you can have a replacement in the cupboard in case your original dies; typicallY ONUs need to be individually provisioned by the ISP but if you have a perfect clone all the ISP would see is a short power-down). The upshot of this is that some found ways onto SFP onus so you can get more information from the ONU if you are really dedicated. But first you need an GPON link and an ISP that will provision whatever ONU you selected... (ITU envisioned the ONU to be part of the ISPs network and hence little thought was spend on ideas like giving the end user root on those devices). And that is where I am out, currently FTTH-built out is a big topic at home, but has not reached my flat yet and might not for a few years (oh, the irony, as I am living literally next door to a central office of the incumbent telco, spanning a fiber cable over less then 20 m should get me FTTH, but I digress)

Regards
	Sebastian

> 
> 
> On Thu, Jan 13, 2022 at 6:51 AM Sebastian Moeller <moeller0 at gmx.de> wrote:
>> 
>> Yes sorry,
>> 
>> in GPON you have the unit at the telco side, often called OLT (optical line termination/terminal or similar, which feeds the whole segment of up to ~128 remote terminals and receives data from all) the passive splitter (if any) and the remote customer units that are called either ONU or ONT, but that are just two names for the same unit (not sure who uses which nomenclature, the local incumbent seems to prefer ONU, but their marketing name is Glasfasermodem, which just translates to fiber-modem). Nomenclature seems ot be consistent for the whole PON family, so in XG-PON or XGS-PON the unit apparently still are called OLT and ONU/ONT. And given that PON requires some smarts and configurability of the ONUs these tend to be small computers in their own right with their own little (or not so little) OSes.
>> 
>> Regards
>>        Sebastian
>> 
>> 
>> 
>>> On Jan 13, 2022, at 15:38, Dave Taht <dave.taht at gmail.com> wrote:
>>> 
>>> And a gpon onu
>>> 
>>> https://www.fs.com/products/133619.html
>>> 
>>> On Thu, Jan 13, 2022 at 6:23 AM Sebastian Moeller <moeller0 at gmx.de> wrote:
>>>> 
>>>> That is similar to what happens in some GPON-ONT SFPs, some run a full small Linux distribution like OpenWrt inside.... though for ethernet that is unexpected.
>>>> This is also similar to SFP VDSL "modems" which likely run their own embedded OS as well inside the SFP package (at a time there was even a PCI VDSL2 "modem" that was actually running its own embedded system on the PCI board, IIRC, it pretended to the main computer to be an ethernet NIC).
>>>> 
>>>> Regards
>>>>       Sebastian
>>>> 
>>>> 
>>>> 
>>>>> On Jan 13, 2022, at 15:18, Dave Taht <dave.taht at gmail.com> wrote:
>>>>> 
>>>>> running linux, of course.
>>>>> 
>>>>> https://blog.benjojo.co.uk/post/smart-sfp-linux-inside
>>>>> 
>>>>> --
>>>>> I tried to build a better future, a few times:
>>>>> https://wayforward.archive.org/?site=https%3A%2F%2Fwww.icei.org
>>>>> 
>>>>> Dave Täht CEO, TekLibre, LLC
>>>>> _______________________________________________
>>>>> Cerowrt-devel mailing list
>>>>> Cerowrt-devel at lists.bufferbloat.net
>>>>> https://lists.bufferbloat.net/listinfo/cerowrt-devel
>>>> 
>>> 
>>> 
>>> --
>>> I tried to build a better future, a few times:
>>> https://wayforward.archive.org/?site=https%3A%2F%2Fwww.icei.org
>>> 
>>> Dave Täht CEO, TekLibre, LLC
>> 
> 
> 
> -- 
> I tried to build a better future, a few times:
> https://wayforward.archive.org/?site=https%3A%2F%2Fwww.icei.org
> 
> Dave Täht CEO, TekLibre, LLC