I think WWWombat has it covered better than I can
Re. stability issues NewtronStar... WWWombat is correct in that it's up to the user to raise it with the ISP. Having raised more line faults than I care to count, the process becomes quite monotonous! You call the ISP, mention stability issues and request a line test. Depending on the agent - they'll either run through the script of
"have you reset the modem, are there any other devices plugged in", etc... or with a good operator, they'll tell you to yank out the modem and they'll conduct a live line test there and then. On detecting a fault, you wait patiently for the magic phrase of
"we'll request an engineer callout" and bingo!!
OK... a little over-enthusiastic maybe but that's basically it. An engineer will call out from either open eir or from KN Networks (our equivalent of Kelly's). They'll ignore the notes from the ISP (they're usually all wrong anyways) and they'll go to work. A good engineer will come equipped with a fancy meter of some description, will usually start in the premises and work backwards. I've found most fixes are completed in an hour but some can take weeks if there's repair work needed on the network but generally, once it's in the hands of the line techs, it'll be fixed and you don't have to waste time arguing with the ISP. That said, it can be hit and miss. I've personally never experienced a bad engineer but others have been let down by missed appointments, non-fixes, bad workmanship, etc... Also, some of the ISP's, resellers in particular, can be a bit miserable about sending an engineer and will instead swamp you with replacement modems for fear of costing the company money I guess. It's flexible though in that if you don't like what a particular support agent is saying, you hang up, call back and talk to someone else!
Behind all this madness, I live in fear that open eir would consider DLM sometime in the future. The introduction of DLM probably wouldn't bother the vast majority and perhaps would save money at the ISP support desks but I guess our days of tweaking SNR's ever lower, swapping this modem for that modem, trying this firmware then that firmware... those ever enjoyable days would be over
... or just less enjoyable
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Re. pre-quals and target SNR's... I'm not sure on the exact science behind the pre-qual tests but yes, it seems open eir run a rule to gauge attenuation for every line and then, if it's a go, they list suitable profiles to the ISP's based on this. I don't know how often the pre-qual tests are run either but the frequency seems to have increased lately, I guess on account of all the VDSL kit coming on-stream. Also, there are method for extracting the results from various public sources using cURL commands which has become a hobby for some! Anyway, for lines passing for VDSL, they suggest both a High Speed profile and a also Non Rate Adaptive for IPTV. For ADSL lines, they'll list a suitable profile which can include additional recommendations for the like of High Interleaving on the downstream, Fixed Rate profile, etc. In exchanges with both ADSL and ADSL2 or 2+ gear, sometimes there'd be 2 sets of profiles listed for the different gens
Again, all of this tends to be flexible and usually you can call the ISP and request to be bumped up or request things like fastpath or higher interleaving on older ADSL connections. Some support agents will decline, others will be happy to bump you up or tweak you and let you decide yourself if it's stable or not. One particular pain point though was requesting a swap from ADSL to ADSL2 / 2+ in exchanges where it was available. Again, miserable ISP's it seemed, refusing to pay for an engineer to nip out and switch the pair between racks but thankfully with the VDSL upgrades ongoing, this type of request isn't as common
Just a note on target SNR's too... I'm not overly familiar on this but I believe the ISP's are following target SNR's but it's not something you hear mentioned too often. AFAIK, some ISP have their own, safer target that they aim for too besides what open eir have advised. That said, on ADSL connections and with a modem with SNR adjustment, you could freely drop the SNR to the floor to get more from your allowable profile speed... or you could raise it to make the line more stable!
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Re. FTTH... I'll develop a little on the prospects of national FTTH, of which there is much discussion on the various Irish forums. My understanding is merely what I've gained from the very informative postings and work of others (who'll hopefully join in here in time)... so it might be patchy or down-right incorrect!
Most of our ISP's submitted proposals to the government last year for the National Broadband Plan. Those ISP's who made serious submissions were touting FTTH as the most feasible solution for a national broadband network. I understand our topography, our one-off housing problems and generally non-clustered population layout in large areas means rolling out FTTH is more economical in the long run, perhaps more expensive up front. Some have rightly pointed out that to cater for the national need using VDSL or (God forbid) fixed-wireless is simply un-feasible due to the sheer number of cabinets or mast sites, planning permission, power supply and civil works that would be required... plus it leaves huge amounts of active equipment to be maintained. This against FTTH where it's run once, forget about it for the next 20 years!
G.Fast is certainly interesting but I haven't heard of any trials or developments around it over here. Have there been any G.Fast deployments in the UK? In my own view, I can't see it coming on-stream here. Others have stated that to go the full slog and drop in FTTH is only slight more expensive if not on-par with mounting G.Fast nodes, powering them and ongoing maintenance. Either way, open eir are well placed to expand with FTTH or even G.Fast as for every VDSL cab they installed, they left 20 or so spare fibres sitting under it for future expansion out to GPON nodes perhaps