[Cerowrt-devel] a smart SFP

Jonas Mårtensson martensson.jonas at gmail.com
Fri Jan 14 08:50:48 EST 2022 

>  Not all ISPs work with a single level of splitters, some do 1:4 and
split each of the four up into more later, I would guess that 1:4 + 1:8
will have a bigger aggregate attenuation than going 1:32 directly, but I am
guessing here, so thanks for the numbers.

It will be slightly higher, mainly due to the extra splices I think, but
other than that there is no fundamental difference between doing 1:32 and
doing 1:4 + 1:8. The fundamental loss is 3 dB per 1:2 split.

> In Germany the law is as it is and requires a passive handover point of
an ISPs network to the home network and also the freedom to choose routers
(and probably also ONTs/ONUs but that is still in flux), so plugs will be
common as will be exchange of ONTs/ONUs by end-users.

That's interesting. I would think that exchanging ONUs is quite tricky (as
also indicated by the "hacking" threads discussed earlier) since OLTs and
ONUs from different suppliers may not even be compatible. Can't the
"passive handover point" be between the ONU and the home router? In Sweden
(where FTTH is very common but PON is almost non-existing), the ISP
normally installs both an Ethernet "switch" terminating the fiber
(typically using an SFP) and a home router connected to the switch using
copper Ethernet cable. While it is common to exchange the home router (or
selecting to not install the ISP's router from the beginning), I don't
think anyone exchanges the switch with the fiber termination and doing so
would probably not work anyway since the switch needs to be "managed" by
the ISP.

/Jonas

On Fri, Jan 14, 2022 at 2:23 PM Sebastian Moeller <moeller0 at gmx.de> wrote:

> Hi Jonas,
>
>
>
> > On Jan 14, 2022, at 14:12, Jonas Mårtensson <martensson.jonas at gmail.com>
> wrote:
> >
> > >  Sure, but given that you probably need a few splices along the way
> and preferably pluggable connectors at both ends the loss budget is not
> that large (assuming an ISP does not want to push its luck and allows for
> stuff like end-users not cleaning the plug diligently before each plugging).
> >
> > GPON loss budget is 28 dB and typical insertion losses for 1:32 and 1:64
> splitters are 17 dB and 21 dB. This leaves 11 dB or 7 dB for splices,
> connectors and fiber losses. I don't think it's common to have end-users
> cleaning and plugging in the fiber, this is done by the ISP technician at
> installation.
>
>         Not all ISPs work with a single level of splitters, some do 1:4
> and split each of the four up into more later, I would guess that 1:4 + 1:8
> will have a bigger aggregate attenuation than going 1:32 directly, but I am
> guessing here, so thanks for the numbers. In Germany the law is as it is
> and requires a passive handover point of an ISPs network to the home
> network and also the freedom to choose routers (and probably also ONTs/ONUs
> but that is still in flux), so plugs will be common as will be exchange of
> ONTs/ONUs by end-users. Whether that is a good or a bad thins is open for
> discussion, but as an ISP I would try to plan my PON plant such that there
> would be more loss reserve for these final connections than would be if
> these would be performed and documented by trained technicians. (I think
> that might be one of the consequences of deploying FTTH in the mass market,
> solutions need to be a bit more error tolerant than for networks mainly
> handled by experts only.)
>
> >
> > > Dslreports has no cue what a link is actually using, all it reports
> wich test profile a user selected, and some users like me ignore the names
> and simply use/recommend the profile with the desired number of flows. Plus
> quite a number of dedidedly metallic access technology are marketed with
> fiber somewhere in the name, potentially confusing users into selecting the
> "wrong" profile (think Fiber to the Cabinet for copper DSL or even
> Hybrid-Fiber-Coax for docsis cable)... in short the abels are nice, but I
> would not read too much inside those.
> >
> > I agree with all these points. It may be better to look at ISPs that are
> known to only use PON, such as Google Fiber. Here are some recent tests
> that all show similar and interesting bufferbloat behaviour on the uplink:
> >
> > https://www.dslreports.com/speedtest/70320015
> > https://www.dslreports.com/speedtest/70346586
> > https://www.dslreports.com/speedtest/70346578
>
> Thanks!
>
> Best Regards
>         Sebastian
>
>
>
> >
> > /Jonas
> >
> > On Fri, Jan 14, 2022 at 12:55 PM Sebastian Moeller <moeller0 at gmx.de>
> wrote:
> > Hi Jonas,
> >
> >
> > > On Jan 14, 2022, at 11:44, Jonas Mårtensson <
> martensson.jonas at gmail.com> wrote:
> > >
> > > Hi,
> > >
> > > >  getting gpon more right has increasingly been on my mind
> > >
> > > I think more right is to not turn the fiber into a shared medium in
> the first place but since gpon is so popular, improving it seems like a
> nice goal.
> > >
> > > > Nobody in their right mind is going to hook up 128 terminalt to one
> OLT port, I hope...
> > >
> > > Well, sharing one OLT port between many terminals is kind of the
> (only) advantage of PON, although split ratios of 32 or 64 are more
> typical. But often it's the loss budget that limits the ratio.
> >
> >         Sure, but given that you probably need a few splices along the
> way and preferably pluggable connectors at both ends the loss budget is not
> that large (assuming an ISP does not want to push its luck and allows for
> stuff like end-users not cleaning the plug diligently before each plugging).
> >
> >
> > >
> > > >  Fist question might to be "how broken is GPON/XGPON" to start with,
> no?
> > >
> > > Looking at dslreports bufferbloat results for fiber, there are many
> samples with >250ms latency on the uplink. Unfortunately, this graph
> doesn't show results for 500Mbit/s or 1Gbit/s services but it's still
> interesting to look at:
> > >
> > > https://www.dslreports.com/speedtest/results/bufferbloat?up=1
> >
> >         Dslreports has no cue what a link is actually using, all it
> reports wich test profile a user selected, and some users like me ignore
> the names and simply use/recommend the profile with the desired number of
> flows. Plus quite a number of dedidedly metallic access technology are
> marketed with fiber somewhere in the name, potentially confusing users into
> selecting the "wrong" profile (think Fiber to the Cabinet for copper DSL or
> even Hybrid-Fiber-Coax for docsis cable)... in short the abels are nice,
> but I would not read too much inside those.
> >
> >
> > >
> > > >  this thread
> https://www.computerbase.de/forum/threads/eigenes-modem-an-ftth-anschluss-via-sfp-gpon-modul.2061989/
> (in German) has some instructions how to get root on one type of SFP ONU...
> > >
> > > Thanks, that's an interesting thread. "Hacking" SFP ONUs seems like a
> popular hobby. Here are some other resources I found:
> > >
> > > https://github.com/zry98/SFP-GPON-ONU
> > > https://github.com/hwti/G-010S-A
> > > https://forum.mikrotik.com/viewtopic.php?t=116364&start=300#p771961
> >
> > Thanks for the links!
> >
> > Regards
> >         Sebastian
> >
> >
> >
> >
> >
> > >
> > > > 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
> > >
> > > Yes, but ideally I guess you would also need some control of the OLT
> side. You may want to look into the VOLTHA project run by ONF:
> > >
> > > https://wiki.opennetworking.org/display/COM/VOLTHA
> > >
> > > /Jonas
> > >
> > > On Thu, Jan 13, 2022 at 5:29 PM Sebastian Moeller <moeller0 at gmx.de>
> wrote:
> > > Hi Dave,
> > >
> > >
> > >
> > > > On Jan 13, 2022, at 16:59, Dave Taht <dave.taht at gmail.com> wrote:
> > > >
> > > > On Thu, Jan 13, 2022 at 7:57 AM Sebastian Moeller <moeller0 at gmx.de>
> wrote:
> > > >>
> > > >> Hi Dave,
> > > >>
> > > >>
> > > >> this thread
> https://www.computerbase.de/forum/threads/eigenes-modem-an-ftth-anschluss-via-sfp-gpon-modul.2061989/
> (in German) has some instructions how to get root on one type of SFP ONU...
> (I was monitoring that thread for general interest, turns out the intel
> falcon plattform seems somehow based on an ancient OpenWrt)
> > > >>
> > > >> Regards
> > > >>        Sebastian
> > > >
> > > > It's really remarkable how many places are running an ancient
> openwrt.
> > > > Starlink's use was not an abomination, but a persistent reality.
> Given
> > > > how much
> > > > chaos calmer I've found, I sometimes wish we'd somehow started the
> > > > cerowrt project 2 years earlier.
> > >
> > >         Yes and no.
> > >
> > > > Then we'd be done by now.
> > >
> > >         Hopefully, but then I would not have noticed the whole thing
> and would probably not have participated... ;)
> > >
> > > 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
> > >
> > > _______________________________________________
> > > Cerowrt-devel mailing list
> > > Cerowrt-devel at lists.bufferbloat.net
> > > https://lists.bufferbloat.net/listinfo/cerowrt-devel
> >
>
>
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