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20 January 2019

Migrated to G.fast 500 Mbit DSL with Turris Omnia and SFP

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In 2018, the building was upgraded to the 500 Mbit G.fast DSL network. G.fast is a fibre-to-the-curb type of service, in this case, the fibre goes into the basement where a DPU interfaces to the existing copper lines.

There are not a lot of G.fast routers out there right now. Local suppliers only have a couple of very expensive proprietary models with features I don't need. I wanted to find a low cost device to act as a bridge with my existing Turris Omnia router.

I then discovered that there are a range of SFPs available for G.fast and as the Turris Omnia has an SFP port, this appears to be a compact solution. MVMTel were kind enough to send me a sample of their EFS-02 SFP to evaluate.

I disconnected my existing VDSL modem, turned off the Turris Omnia, inserted the SFP and turned on the Turris Omnia again. When an SFP is inserted, it takes over the existing configuration of the ethernet WAN port where the VDSL modem was connected. In this case, that meant no changes to the configuration were necessary, it was completely plug and play and started working immediately.

It's been running for a few months now and I've made a few observations about the service.

One of the first things to be aware of is that the SFP doesn't support any legacy DSL speeds, only G.fast, so if the device is moved to another location without G.fast, it just won't work. This limitation comes about due to the challenge of fitting everything into the SFP form-factor.

I've also had the same router on a fibre-to-the-home service in Zurich, with a fibre SFP. Looking at Smokeping, I've observed that latency with FTTH was just under 1ms, with G.fast it is about 4.5ms and with VDSL it was about 9ms.

One afternoon there was a momentary glitch in the electricity supply. All my equipment continued operating normally on UPS but the G.fast connection went down and took a couple of minutes to come back up. This left me with the impression that the DPU in the basement may be running off mains power without any battery backup. Fibre doesn't deliver power from the exchange in the same way that copper does.

Here is a photo of the SFP in the back of the Turris Omnia, the SFP is on the right hand side:

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