2018-01-19

VDSL SFP and FireBrick

The FireBrick has been around a while, and over the decades we have moved through many versions with a new FB2900 nearly released. We are playing with the prototypes now.

One thing we have never done is include a DSL modem in the FireBrick, and people do occasionally ask why.

I'll be quite frank and explain that FireBricks are designed to last a long time. We have people using FireBricks that are well over 10 years old now and going strong. Including a DSL modem would mean a much more aggressive design cycle as modems are improving all of the time and so are technologies. Basically, we would never keep up. So stick to what we are good at.

Of course, one of the other issues is that one of our main target customer groups is those using multiple lines for bonding, so how many modems do we include exactly?

But a two box solution is not nice, separate modem and FireBrick is not always ideal. Well, we may finally have a way to address this, at least for single line installations.

The new FB2900 has an SFP slot. For those that do not know, these allow a module to be inserted to provide the actual media interface for an Ethernet port. Typical examples are fiberoptic connections or a normal copper cat 5 connection.

What is interesting is that someone makes a SFP module that does VDSL and even ADSL. It looks like an Ethernet media device but actually synchronises and does ADSL or VDSL modem signalling.

The biggest issue is they are very poorly documented. However, for VDSL, we have found that they "just work" in every sense. You plug it in, and it appears as a 1Gb/s Ethernet port, but you then talk PPP VLAN 101 as you would to a separate bridging VDSL modem (unless it maps the VLAN for you, as many do). It talks to the BRAS and goes on line, even handling 1508 baby jumbo frames to allow 1500 MTU PPP.


The one downside is that it uses way more power than the SFP specification, but it seems the FB2900 power supply is up to the job. It may be the only time anything in an FB2900 gets remotely warm.

End result, a combined single box modem, router, and firewall box, and it's a FireBrick. So reboot time under a second, and PPP reconnect time under a second, IPv6 as standard, and much more - little things like that. Not your average router by far.

Some technical notes:

The VDSL works as a standard bridge, and so for typical UK VDSL broadband needs PPPoE over VLAN 101.

For ADSL there seems to be some mapping of VLANs to VCI/VPI but documentation is sketchy and we have yet to find the normal 0/38 mapping used in the UK.

VDSL SFP from Proscend.

P.S. Just noticed the MAC address. So Proscend have 000379 and FireBrick have 000397. That won't be confusing at all :-)

28 comments:

  1. That's really interesting. I've just used SFP for the first time to turn the two SFP ports on my Ubiquiti 8 port 150W POE switch into additional gigabit ethernet ports, making it a 10 port switch.

    I guess, except for the whole NAT side of it, this could turn many switches into a switch/modem combo...

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    1. The device the SFP is plugged into still needs to be able to manage the PPP session, so it won't be possible to convert a switch into a router.

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  2. They even have G.Fast coming soon! You're future proof! ;)

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  3. I've seen these before, but this is the first time I've heard of anyone testing then. Glad to hear that they seem to work just fine.

    I see that company is based in Taiwan, and they list no pricing info on their website.

    Can you give any info on cost/delivery time, and are they happy to sell low volumes (1-2).

    Alternatively are AAISP planning on reselling them?

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    1. I would definitely be interested if anyone's found a european supplier or if AAISP are going to resell them.

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    2. I found these: https://www.mikrotik-shop.de/Interfaces/SFP/Kupfer/SFP-VDSL2-Modem-Telco::2192.html

      Appear to be the same thing. Not the cheapest!

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  4. Has the SFP been through (or are you intending on putting it through Openreach MCT testing)?

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    1. I doubt it and I doubt is, so just as well that it is not a requirement (as per EU net neutrality rules).

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    2. Do you mind commenting on why OpenReach MCT wouldn't be required? I thought all VDSL devices on their network had to be SIN 498, otherwise OR/BT won't assist when there's a line fault involving a non-compliant modem? (My understanding could be completely wrong!)

      Also, any way to get VDSL/ADSL statistics like SNR etc from these? I've read the Mikrotik forums about them, doesn't look like it's possible. Just wondered if you had seen something they hadn't.

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    3. Because net neutrality law does not allow BT to restrict the terminal equipment to devices meeting SIN498, that is why!

      We cannot legally require customers to only use MCT. BT cannot require is to break the law by us making that requirement on customers.

      As for faults, the fault repair is on the service which has a clear demarkation point - the master socket - there is (as far as I know) no requirement for *ANY* equipment (MCT tested or not) to be attached to the line when the engineer arrives to fix the fault. If their service does not work to spec at the demarcation point they have to fix it, end of story.

      These specific devices may not be ideal, but BT trying to lock down what terminal equipment people use is not lawful, simple as that.

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    4. Very interesting, thank you for the insights!

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    5. Er you are talking a bit of nonsense there. Net neutrality has nothing to do with it at all. However you are right the MCT stuff is illegal because approval is done at an EU level not on a per country level. It's not much of a single market if a manufacturer of a VDSL2 device has to get it approved in every individual country. It's why you don't see those BABT approval stickers anymore. Frankly BT should be reported to OFCOM for breaking EU law with the whole SIN498 thing.

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    6. Well yes, that is the approval system, and hence CE mark. Net neutrality also applies. I.e. an ISP cannot say "you must use only our (approved) equipment on this service". Without that you could have approved equipment under a unified EU wide standard but a contract that says you cannot use it on a specific service. So I think net neutrality matters as part of this. Both parts matter.

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    7. You are correct that BT cannot restrict terminal equipment to devices meeting SIN498, but the reason for this has nothing to do with net neutrality. Basically approval of telecommunications devices is done at an EU level these days. Not much of a single market if you have to get your VDSL2 device approved in all 28 countries. As a consequence the whole BT SIN498 thing as presented is flat out illegal, and really OFCOM should be taking BT to tasks over it.

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    8. You may be missing my point slightly - I completely agree, EU wide approval mechanism - that means any approved modem can *legally* be connected, but without net neutrality it would be possible for such connection to be a breach of *contract*. Net neutrality adds the extra step of not allowing an ISP to constrain the equipment (other than being CE marked / EU wide approved) in contract even. An important extra step. I am not sure EU approvals actually stop contracts restricting things, on their own.

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  5. Who did you purchase your module from?
    Is there a European reseller?

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    1. I am not sure at the moment, we have a couple.

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    2. We purchased from the manufacturer last year. Not aware of a EU reseller at the moment though.

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  6. Theres also https://www.versatek.com/product/vx-160ce-vdsl2-sfp-modem-remote-telco-grade/ - spec looks similar, $105

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    1. They are the same modules according to the RouterOS thread.

      Apparently there is also a Windows tool which can change some config on these using Ethernet.

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  7. Have you also considered supporting GPON OLT SFPs?

    https://www.fs.com/products/64168.html

    How hard could it be? :-)

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    1. As the SFP has to appear as an Ethernet device there is little for us to “support”. I expect they would just work.

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  8. This thread may also be useful. A few folk have been using these with RouterOS too: https://forum.mikrotik.com/viewtopic.php?f=3&t=104109&start=200

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  9. They are 2.48g tx and 1.25 Rx for running complex ATM/tdm protocols they absolutely would not work !!!! This absolute gibberish that any sfp works in a MSA 1GBe sfp port is shocking - sfp is a form factor! No standard to force it to support ethernet.

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    1. The back end is serdes and if they want people to plug in to switches, which is presumably why they chose that form factor, they would make it talk 1Gb Ethernet frames. The modem we are testing also does ADSL which is ATM but it does the LLC to bridge Ethernet frames. So I expect that they would find a way.

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  10. It would nice if AA could resell these, as proscend appears not to offer them to consumers.

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  11. I have one of these SFP's too...and while it seems to sync up on my DSL line I'm not seeing any traffic inbound on the SFP port regardless of what VLAN I'm looking at. The documentation for these is very limited to say the least.

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