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I have a VDSL (G.993) connection to my home.
I have brought and previously successfully used this SFP VDSL modem on my Turris Omnia (an OpenWRT Linux based router): https://www.versatek.com/product/vx-160ce-vdsl2-sfp-modem-remote-telco-grade/
This set up worked on a similar connection with the same ISP at the same speed rating on a different telephone exchange (in the same country):
However, I've now moved house and the SFP modem is unable to successfully negotiate a link (LED 2 flashes, intermittently fast).
The vendor supplied consumer grade router works flawlessly. Here are the log lines showing successful link negotiation:
Jan 1 00:00:19 syslog: [ 19.874000] Line 0: xDSL G.994 training
Jan 1 00:00:21 syslog: [ 21.878000] Line 0: ADSL link down
Jan 1 00:00:47 syslog: [ 47.889000] Line 0: xDSL G.994 training
Jan 1 00:00:56 syslog: [ 56.896000] Line 0: VDSL G.993 started
Jan 1 00:01:14 syslog: [ 74.931000] Line 0: VDSL2 link up, Bearer 0, us=9995, ds=39994
Jan 1 00:01:30 syslog: DDNS update successful
Jan 1 00:01:31 syslog: ptm0.1 - WAN link UP.
Unfortunately, on the Turris Omnia with the SFP, the OpenWRT logs do not help much: I'm fairly sure link negotiation happens within the SFP itself which then presents the negotiated link to Linux as PHY.
Because of this, the finance department (the wife) wonders whether £300 spent on a router was a good use of company funds ;)
Does anyone have any tips on how to debug this? Perhaps a way to debug what is happening on the wire? Can I get more relevant information about the physical device through the command line?
The problem could be something as simple as a poor connection to a pin on the SFP or, as I suspect, it may be due to incompatible equipment at the exchange.
I searched online for DSL tap and couldn't find anything that would help. I am not a professional network engineer; any tips on how to take debugging of this further would be most appreciated.
Mark
Posted 2020-02-23T11:31:48.913
Reputation: 133
The VDSL2 modem does not support Annex J (only A/B/C). Do you perhaps have Annex J now? – Daniel B – 2020-02-23T12:16:32.853
@Daniel B how can I confirm this? – Mark – 2020-02-23T12:28:01.387
Dunno ask your ISP? Maybe also look for the specs of the ISP-provided modem. Maybe the ISP device has a status page with technical information. – Daniel B – 2020-02-23T12:30:44.073
@DanielB I phoned my ISP and they had no idea what I was talking about. Couldn't find much info on the topic of Annex standards but, from looking at multiple posts about the UK market, it seems it's most likely to be Annex A (https://community.plus.net/t5/My-Router/Asus-DSL-AC56U-what-annex-setting/td-p/1422184 and https://www.ispreview.co.uk/index.php/2018/06/2018-update-best-vdsl-routers-for-uk-fttc-fibre-broadband-isps.html/2). There's nothing on the router about the Annex (I've posted all the log info available on the webif already).
– Mark – 2020-02-23T13:03:45.267@DanielB Reading a bit more (https://en.wikipedia.org/wiki/G.992.3_Annex_J), Annex J is an ADSL technology. This line is VDSL (G.993). So I don't think this would be the problem. Thanks for the tip though: interesting to read a bit more around the topic.
– Mark – 2020-02-23T13:20:57.4372I used to develop firmware for HDSL (the slower predecessor to VDSL) units at a leading company. Development of the training sequence was specifically handled by one expert. I could read about the steps involved in training (e.g. checking power levels,checking echo, measuring signal-to-noise, setting equalization), but was clueless if training failed. It requires coordination between the master (or line) and slave (CPE) units, and is treated as a go/no-go test. IOW it's an esoteric subject. Check the labels on the ISP-supplied modem vs the SFP regarding ITU standards. – sawdust – 2020-02-23T23:51:34.847