Niall’s virtual diary archives – Thursday 24 April 2025

Thursday 24 April 2025: 21:50. Yet another not a house post this time, but in fact I originally wrote one very long post which was about three completely independent topics. So it made more sense to break them up into individual days. This one is about fibre broadband in Ireland, and the new fibre broadband just installed into my rented house.

A few months ago, our vDSL connection disappeared and when the man came out to fix it, he said the line had gone so he switched us over to another line. This new line synced at about 30 Mbps rather than the 92 Mbps we got before, and kept dropping out for twenty minutes or more at a time. This was similar to when we first had vDSL put in – I had to have the repair guy out many times until one of them finally came up with a stable vDSL solution. That had lasted since then until now.

Thankfully Ireland now has better options! You can now get fibre installed into the premises for free if you sign up to a twelve month contract. A man appeared about three weeks ago, he installed an additional cable from the pole into the current rented house, and voilà I now have a direct fibre internet connection to the world.

In my post about fibre to the premises in Ireland, it turns out I incorrectly stated that Ireland uses multi-mode fibre for the last mile. This is true in other countries, but I have since learned that Ireland went with single-mode fibre for its GPON (Gigabit capable Passive Optical Network) last mile solution throughout as we tend to have more sparsely populated urban settlements and it was easier to deploy one unified solution. Thus, in Ireland, every premises gets its own dedicated fibre pair from the ONT (Optical Network Terminal) within the premises back to the cabinet to your own dedicated port on the OLT (Optical Line Termination) card. That card is very similar to a managed switch, and it shares an upstream fibre connection between up to 128 ports i.e. premises, though it’s usually less than that (supposedly, always less than 64 in Ireland). You might then get a 2.5 Gbps uplink from the OLT to the backhaul carrier, which therefore has up to 64 premises sharing it.

The physical fibre backhaul in Ireland for historical reasons has three independent implementations: (i) the ducts of the historical telephone network, which tends to follow major roads and motorways (Open Eir) (ii) the ducts of the power supply network, which connects mobile phone towers (SIRO) (iii) where the government has spent public money on installing fibre where it is commercially not viable to otherwise do so (NBI). To make things a bit more confusing, the owners of the physical fibre are not always the operators nor maintainers of that fibre, and there has been an ongoing government push to consolidate everything under a single one stop shop – however, for now, it all remains a patchwork and there are separate OLTs for fibre from the historical telephone network (Open Eir) and for fibre from the power supply network (SIRO). So, to be specific, if I order fibre broadband from an ISP which uses Open Eir for the backhaul and when that contract ends I order fibre broadband from an ISP which uses SIRO for the backhaul, I get two ONTs with two fibre cables installed into my house. They hope to fix that by year 2030, as that’s obviously daft, but it will require new laws to be passed so there it is.

SIRO due to its physical trunking along major power cables tends to mainly appear only in urban centres, so for both my rented house and my future house being both rural the only backhaul fibre connectivity available is Eircom’s fibre network which for rural Ireland is usually the nearest ‘N-road’ which is the type which connects major towns, which eventually feed into the motorway system which ultimately ends up arriving into Dublin. In other words, if you follow the roads, you can say how the data flows which makes things a bit easier.

What happens next is a bit more complicated. The physical fibre moves the bits of data, and as far as I can tell there appear to be several Layer 3 packet switching network implementations some of which share the same duct, but may use physically separated cables or even separated fibres within the same cable. As of Q3 2024, 1.3 million premises were connected to the Eir fibre network; 609,000 to SIRO’s fibre network and 300,000 to NBI’s fibre network. There isn’t much public information about how all this hangs together, so I apologise in advance if this post also contains mistakes – I gleaned most of this off social media where network engineers say how they think things work (which isn’t always correct either I’ve noticed).

I mention all this detail because the fibre installed to the site uses the Eircom Layer 4 backhaul, whereas my rented house uses the BTIreland Layer 4 backhaul. I read online that ISPs can choose to run PPPoE or IPoE over the backhaul, and ISPs who use multiple wholesale networks tend to choose PPPoE because then they can mostly ignore which wholesale network is the backhaul, and treat the lot as if a single network. What this means, of course, is all traffic must go via Dublin if PPPoE is used, whereas it doesn’t if IPoE is used.

Let’s see this in practice:

From rented house to site:

traceroute to 217.183.227.33 (217.183.227.33), 30 hops max, 46 byte packets
 1  lo1001.bas101.cwt.btireland.net (193.95.131.6)  8.949 ms  10.137 ms  9.245 ms
 2  be137-50.rt101.cwt.btireland.net (193.95.152.1)  7.961 ms  11.220 ms  8.181 ms
 3  be103-100.core201.cwt.btireland.net (193.95.129.239)  8.915 ms  be104-100.core202.cwt.btireland.net (193.95.129.241)  9.419 ms  be103-100.core201.cwt.btireland.net (193.95.129.239)  8.204 ms
 4  be204-100.rt102.cwt.btireland.net (193.95.129.244)  9.345 ms  be203-100.rt102.cwt.btireland.net (193.95.129.242)  12.443 ms  9.375 ms
 5  lag-40.br1.6cr.border.eircom.net (185.6.36.82)  8.567 ms  11.518 ms  8.825 ms
 6  eth-trunk21.hcore1.prp.core.eircom.net (86.43.12.214)  14.236 ms  11.549 ms  20.680 ms
 7  eth-trunk11.hcore1.lmk.core.eircom.net (159.134.123.10)  18.473 ms  17.230 ms  16.650 ms
 8  lag-1-agg3-mlw-hcore1-lmk.agg3.mlw.lmk-mlw.eircom.net (86.43.253.149)  15.396 ms  15.442 ms  18.941 ms
 9  217-183-227-33-dynamic.agg3.mlw.lmk-mlw.eircom.net (217.183.227.33)  17.578 ms  18.452 ms  20.854 ms

From site to rented house:

traceroute to 194.125.122.54 (194.125.122.54), 30 hops max, 46 byte packets
 1  217-183-226-1-dynamic.agg3.mlw.lmk-mlw.eircom.net (217.183.226.1)  2.635 ms  3.926 ms  3.776 ms
 2  eth-trunk122.hcore1.mlw.core.eircom.net (86.43.253.150)  8.553 ms  3.782 ms  3.742 ms
 3  eth-trunk15.hcore1.prp.core.eircom.net (86.43.254.143)  19.218 ms  10.235 ms  10.804 ms
 4  *  *  *
 5  inex1.btireland.net (185.6.36.166)  9.500 ms  8.894 ms  8.884 ms
 6  be103-100.core201.bmt.btireland.net (193.95.129.161)  5.781 ms  9.060 ms  8.759 ms
 7  be304-100.core202.cwt.btireland.net (193.95.129.83)  8.706 ms  be304-100.core201.cwt.btireland.net (193.95.129.85)  9.394 ms  be404-100.core202.cwt.btireland.net (193.95.129.87)  8.888 ms
 8  be104-100.rt101.cwt.btireland.net (193.95.129.240)  10.145 ms  10.076 ms  10.875 ms
 9  po2.bas101.cwt.btireland.net (193.95.152.7)  10.364 ms  9.766 ms  9.866 ms
10  194.125.122.54 (194.125.122.54)  20.493 ms  17.644 ms  17.767 ms

(In case you think I am leaking my IP addresses, by the time you read this they will have been rotated – both are allocated by the ISP via dynamic DHCP and they change every few hours)

Geolocation works for these IPs! For site to rented house:

1. Mallow (Eircom)
2. Limerick (Eircom)
3. Citywest, Dublin (Eircom) – note I think this wrong, see below
4. Dublin Internet Neutral Exchange Association (INEX), which is where a lot of Ireland’s internet traffic gets peered.
5. Saggart, Dublin (BTIreland/Esatnet)
6. Swords, Dublin (BTIreland/Esatnet)
7. (Remaining IPs all geolocate to Dublin thanks to the PPPoE until …)
8. Cork (BTIreland/Esatnet)

I think the geolocation database a bit off though – in the traceroute, prp.core.eircom.net looks like Priory Park Telephone Exchange near Mount Merrion in Dublin, not Citywest; lmk.core.eircom.net looks like Roches Street Telephone Exchange in Limerick; mlw.core.eircom.net looks like some exchange in Mallow. cwt.btireland.net does look like Citywest instead.

This is the problem with my rented house’s ISP using PPPoE. If my rented house were also on Eir for its broadband – and because Eir only use their own backhaul exclusively – traffic between the two sites wouldn’t leave the Mallow switch and round trip ping times would be under three milliseconds. By forcing everything via Dublin, we get eighteen milliseconds instead. In case you are wondering if Eir’s Limerick node will route traffic destined for North America directly without it going via Dublin, unfortunately not – I assume it must go to Dublin to get routed onto whoever provides transatlantic cabling.

You’re probably wondering ‘get to what we care about – how fast is it?’:

The download speed is gated by the new G.hn powerline adapters I installed, which do at least go 3x faster than the Homeplug AV2 ones they replaced, and my testing of those did show they capped out on my rented house’s AC wiring at pretty much exactly that speed. So I’ll never see the full 500 Mbps the connection is supposedly capable of, but 345 Mbps is perfectly respectable especially when we got 92 Mbps under the former vDSL.

BUT there is more to a broadband connection than how it performs when the wind is blowing right. We began to notice slowdowns and disconnections, so I put a ping trace on both the rented home fibre broadband and onto the site’s fibre broadband connection. It pings the outermost node in BTIreland’s or Eir’s network every thirty seconds (i.e. their Dublin termination node), and these are a week of measurements up to last Monday:

So, firstly, yeah the BTIreland backhaul clearly has congestion problems in the evenings, there is a clear repeating spike in latencies in the second half of each day. There are also stability problems where the connection will randomly just hang and it takes a minute or two to renegotiate the PPPoE connection. There doesn’t seem to be a pattern to this – Wednesday on the graph was particularly bad, yet Sunday-Monday has been solid.

I showed these graphs to the ISP’s customer support and they said that because I wasn’t using their router, there would be zero support. It’s what you get for €35 per month I suppose. Eir costs €74 per month so it’s double the cost (albeit for a 1 Gbps connection instead of 500 Mbps).

Eir’s backhaul, in comparison, seems to never experience congestion at all. The one (mild) ping spike on Saturday is because my children turned on the TV at the site, which then synchronised the media library with home which meant the connection ran flat out for a few minutes as lots of data got moved. Even then, ping times went from less than ten milliseconds to less than fourteen milliseconds. Not bad, Eir.

In case you’re wondering if BTIreland’s connection is being presented unfairly here, I can tell you we don’t stream anything over the internet. Yes it’s a more actively used connection than the site connection, but when we max it out is usually in the early hours of the morning where no ping spikes appear. This makes sense – what is throttling the maximum download speed is the powerlink connection, not the fibre connection, and I believe G.hn has a separate priority queue for ICMP.

I tried my best to figure out how the PPPoE implementation is routed to BTIreland in Citywest. I didn’t find out a conclusive answer, so I’m going to assume it is routed over Eir’s fibre and that the traffic congestion issues are within its Citywest data centre. The connection reliability issues may be the Powerline network, they may be the fibre between here and the pole, the cabinet or anything else. Or it could also be a Citywest capacity issue. I can’t really tell without a lot more work, and in the end it is ‘good enough’.

One thing I did learn is that almost all ISPs apart from Eir use PPPoE over fibre in Ireland. This makes sense for them, Ireland is a small network so a single IPv4 range could traverse all wholesale providers as a single network. But PPPoE isn’t without overhead, both in terms of ‘routing stupidity’ but also in CPU and network overhead. IPoE is definitely preferable, and Eir is currently the only ISP in Ireland guaranteeing that.

In fairness to Eir fibre broadband, you do get a nearly static public IPv6 /56 allocation – I say nearly static because I’ve never seen it change yet in a year, but because it’s handed out by DHCPv6 and Eir gave me no guarantees, it could change. The IPv4 address does change frequently though, leases are only one hour long and they appear to change every few days. OpenWRT makes setting up dynamic DNS easy, so the Wireguard VPN between the sites is never out for more than a few minutes.

My ISP using BT Ireland does not support IPv6 at all incidentally. From my experience to date, I think I’ll be sticking with Eir when we move into the new house. This is despite that, from my limited testing, international peering appears to better for BTIreland than for Eir e.g. I get 228 Mbps from New York to rented house whereas just 159 Mbps from the same New York provider to the site. Similarly, my colocated servers in the Czech Republic actually have no peering at all because it is Vodafone/BT networks all the way between home and the colocation.

Still, reliability and consistency trumps peak performance, and on that Eir is well ahead of BTIreland.

#broadband #internet