ADSL works over wet string (2017) | Hacker News Reader

ADSL works over wet string (2017)

revk.uk

273 pointsfanf2109 comments

100 Mbps Ethernet over barbed wire was demonstrated back in 1995. [0]

"Only four properties really affect the performance of most digital transmission structures. The "big four" transmission-line properties are impedance, delay, high-frequency loss, and crosstalk." Dr Johnson then goes to describe these properties in barbed wire.

0: https://www.sigcon.com/Pubs/edn/SoGoodBarbedWire.htm

P.S. Yes, this is the Dr. Howard Johnson of the famed "High-Speed Digital Design" book.

And a hundred years before that, you had farmers running DIY phone setups over their barbed wire fences [1].

[1] https://gizmodo.com/barbed-wire-fences-were-an-early-diy-tel...

“ Each house had its own distinctive ring—two short one long, for example—and it was considered impolite to listen in on another's call.”

https://en.m.wikipedia.org/wiki/Party_line_(telephony)

A party line! Our cabin still has a grandfathered one with the distinctive ring. I think we pay 1/4 of the regular rate so we keep it despite everyone having a cell phone now.

I don’t think there’s anyone else on the line.

Got a funny spam call with a recording for some miracle septic tank treatment. It asked me to press 1 for more information and I can’t do that on a rotary phone. Scammers don’t understand their target market. (We also don’t have septic system, just an outhouse.)

What’s the baud rate on that setup like?

“3.” “3 Mbps?” “No. 3.”

I recall reading about one of the last public ones to get replaced back in the late 80ies, somewhere remote in Idaho.

Here we go - 1990: https://www.washingtonpost.com/archive/national/1990/07/13/p...

I guess you can, but your phone sends impulsions instead of DTMF tones, that nobody understands anymore. I'm surprised you can dial out actually

I got a 'digital phone line' through the local cable company installed about a decade ago. I had it hooked up to a rotary phone and I was able to dial out just fine with it.

Pulses can be detected by modern stuff just fine, when said detecting occurs on the same electrical circuit that the phone is connected to (for example, an analog to VoIP interface). They just can't be detected on some other circuit that has only the audio, for example when a conversion to digital audio has occurred. Only tones make it through such conversion. And while a VoIP interface capable of detecting pulses will happily do so (and convert them into something more useful) when it is presenting a dial tone, it won't do a conversion to DTMF for the benefit of IVR [0] mid-call. Devices specifically design to perform this task, however, will!

[0] https://en.m.wikipedia.org/wiki/Interactive_voice_response

> It asked me to press 1 for more information

If you have absolute pitch, and have a friend with absolute pitch (and I mean absolute frequency really not pitch), and are both freaks who can sing perfect sine waves... you could sing the dual tone for number 1 (697 Hz + 1209 Hz).

Since at this point we are talking about mutant alien phreaks, you should also be able to do overtone singing and squeeze out a 2 or a 3 column on your own which are 10% flat and sharp from the 2nd order harmonic of the first row 697 Hz.

Happy phreaking

> freaks who can sing perfect sine waves

Whistle, don't sing. Try it with a realtime analyzer which shows the fundamental being far more prominent than any harmonics above it, which means it's close to a sine wave. Then sing various vowels which will show as a series of harmonics whose amplitude ratios change per vowel but are never reduced nearly as much as when whistling.

I remember Van Jacobson saying in the early 90s that IP would work over two tin cans and a piece of wet string. For several years, I set this as a possible student project, partly as a joke, but it was had no takers for quite a few years. Then in 2009 a student finally took me up on the offer. The main things we learned were that the tin cans were a bad idea (undesirable resonances), and that you could either do on/off coding at the string's resonant frequency, or try to stay well away from the resonant frequency, but then the signal strength was very low but you could distinguish multiple frequencies so do more interesting coding. In the end the project was successful, but the student ran out of time before he could really investigate in great depth.

What an awesome project!

Was the bandwidth that narrow at the resonant frequency? Intuitively, I wouldn't have expected that "wet string" has a high Q. :)

If I had been your student, I would have had great fun with it.

Resonace/ringing is essentially the enemy of bandwidth. Consider a taut guitar string... you can't change its magnitude easily.

What do you mean, cannot change its magnitude easily? I can just pluck it harder or softer? Do you mean frequency response?

And the bandwidth of a resonant circuit depends on its Q. Hence my question about a wet string’s Q, which might well be different from a guitar string’s Q.

https://www.allaboutcircuits.com/uploads/articles/series-res...

What happened if a carrier pigeon landed on the line?

This is funny. About 10 years ago, I had bonded ADSL for my internet (yay sonic.net). The idea being that two lines bonded together would have twice as much bandwidth as a single line. Each line had a max rate of 20Mbps, so I had a max of 40Mbps combined. It worked pretty well initially, but over time it degraded horribly. Because you could see stats for each line independently, I could tell that one line was operating at ~18Mbps and the other was around 2 and there was a lot of error recovery going on. After much complaining, I found out that one line was degraded and somehow reacted to rain (water got in the trunk somehow). And no, AT&T wasn’t going to fix the broken line.

I chose to just use the single (good) line.

So, yes, I can confirm this does work in the field… but with about as much practically as you’d expect.

I’m always a bit amazed when every home has 2 lines running to it, and probably 99% of those second lines never get used, but telcos figured it was worth it for those occasional 2nd lines/fax lines or redundancy instead of ever needing to run a 2nd pull.

Is this just a North America thing or an everywhere thing?

You could always move a line to another pair if one went bad. Not sure if that was part of the motivation or just a happy coincidence.

I'd guess that back in the 80's and 90's those 2nd lines were used a lot more than 1%. Nowadays I wonder if even 1% of a single line is used. ;)

Only two? Around 1995 we had four phone lines: home, home office, fax, and modem. There were only three physical pairs, so two of the lines (I think the voice lines) came off one physical pair with a frequency division splitter.

Some time later I saw a Pacific Bell truck and crew trenching the street. (We had underground utilities.) I excitedly asked them, "Are you running fiber?" "No, just more copper."

I guess they saw the demand for lots of copper lines per house and decided to meet it!

The underground phone lines did lead to some excitement one time. Their water sealing wasn't very good, and after a heavy rain the line would get noisy and clicky. During one of these episodes, we got a loud knock on the door: "San Jose Police! Open up!"

I ran to the door and asked what was going on. One of the officers said, "We got a 911 call from this address. The dispatcher couldn't hear anyone on the line, and no one answered when they called back. So we're required to come out and investigate the situation."

I replied, "That's odd, neither of us called 911. Oh... I think I know what may have happened. Come in and I'll show you."

We went to the kitchen and I put the wall phone (remember those?) on speaker and had the officers listen. It was clicking up a storm!

Then I asked them if they remembered the old rotary phones (they did). I explained how the phone dial worked by breaking and making the circuit N times for each digit you were dialing. And it must have been that in that flurry of clicks that the circuit was broken nine times, then once, then once again.

In India it was pretty common for phones put in semi-public locations to have a lock on the dial to stop people making outgoing calls. But if you were motivated enough, you could still dial out by tapping the number out on the switch hook.

> Some time later I saw a Pacific Bell truck and crew trenching the street. (We had underground utilities.) I excitedly asked them, "Are you running fiber?" "No, just more copper."

During the Australian NBN^^ rollout. Where I used to live was on the border of a FTTC and a coax/DOCSIS one. My street had no pre-existing cable TV cable so you'd think no brainer to lay fibre. Nope, brand new coax. And because the street had no coax that meant no homes had an existing cable so they had to trench every driveway to connect it to the street. It would have been an absolute no brainer to run fibre then use the existing phone lines up driveways to their homes. Cheaper, and an easy upgrade path to full fibre. This was 2019.

^^Australia built a national broadband network. It was originally designed to be all fibre (except for remote places over satellite etc), but politics happened and it was changed to a multi technology mix which included DOCSIS, fibre to the node then vdsl for the last km or whatever, or fibre to the curb and vdsl up your driveway. And the government entity building it NBN was buying up old copper phone lines and coax.

In Germany, the government of Helmut Schmidt (social democrats) planned to implement an optical network to every house in west Germany in 1981. In 1982 Helmut Kohl became chancellor, cancelled the 30 year plan and what we got was coax lines for cable TV. Thanks a lot, just imagine where Germany could be today … to be fair, a significant part of households gets their internet connection over the cable tv networks, but still it was a dumb decision.

German article on the matter:

https://netzpolitik.org/2018/danke-helmut-kohl-kabelfernsehe...

Don‘t forget that Helmut Kohl was also sharing a bed with the television industry at that time when optical networks couldn’t transmit analogue television.

He was a filthy, corrupt man.

Standard neoliberal bullshit coupled with a lack of imagination as to how things like local-loop unbundling might be used to create a competitive market. The UK is now in a fairly good position re broadband, but it could be so much better.

It might have dialed 112, as that sometimes also links to 911 (and 112 is much easier to accidentally dial).

If you go everywhere, you'll rapidly find countries where landlines didn't get meaningful penetration outside of metropolita areas at all.

But even in North America, I don't think every home had two pair all the way to the central office. They might not even all have two pair all the way to the crossbox [1]. It was not uncommon to order a 2nd phone line, and not be able to get it, because there weren't any available pairs on your pole. Especially if your neighborhood was established well before the explosion of the internet and fax in the mid to late 90s.

[1] https://en.m.wikipedia.org/wiki/Serving_area_interface

Very common across Europe too. Makes sense, running a second line is so much labour that only a few would have to order it to make the extra cable cost for everyone worth it.

It's also all the wiring in the walls, too. They all carry two lines, and you could even buy "two line telephones."

It made a lot of sense when I ran a dial-up BBS, or for homes that were heavy modem users. Otherwise, once high-speed internet was an option, 2nd lines made less and less sense.

the telcos used to pressurize cables in order to keep water out of it

http://www.airtalk.com/newsletter5.html

Did you have to pay twice the base price for the bonded ADSL setup?

Another issue with DSL bonding is crosstalk, which is pretty bad in many cases of telco wiring.

10 years ago there was a huge amount of surplus Cisco 1700s with SHDSL line cards (apparently coming from Czech government's project to connect every school to internet in early 00's) and we had huge spool of flat phone cable that was left over from earlier project. So we had the bright idea to wrap ethernet trafic in AAL5, pass that over SHDSL and use that as an LAN for anime convention. Interesting observation from that it matters whether the cable is coiled or un-coiled. We built and tested the whole network in a lab (with coiled cables), it worked well, the G.991bis bonded links synced up at 6Mbps with two pairs and everything was good. We labeled everything and we built the exact same thing (including same cables) at the venue and the links will not go above 1.5Mbps and were frequently losing sync. Disabling the second bonded pair caused it to work reliably at 2Mbps. (Back then, we did not need that much of bandwidth, it was essentially for few SCCP phones, some IP tunelled serial ports and ssh)

Well, next year we bought two boxes of Cat5 cable and switched to native ethernet (and today the backbone spans are 10G fiber, as it also carries video streams).

Ah yeah, if it was just flat cable instead of twisted pair or coax, coiling the cable could have made a massive difference in the characteristics. Interesting that coiling worked better...

We had a serious degradation in line speed every time it rained. We rang our isp (Andrews and Arnold, the same as in the original post), and it was fixed in a week. Thanks A&A!

They have somehow mastered the dark art of persuading Openreach to actually fix things

I think the secret is that they are small enough to be a constant hassling nuisance, so OR now knows that they’ll just get grief until it’s done. Squeaky wheel and all that :)

Well of course, I assume that's what my ISP is using.

Telekom Germany?

Has to be, it would explain my experience.

Could just as well be NBNco in Australia

Rogers in Canada?

I believe Rogers are running DOCSIS-over-Sewage, the competing cable standard.

Nawh, they're using ATM over finches. Those squeaks and chirps you hear outside are actually your packets.

I’m surprised they didn’t stick with the standard RFC 2549

https://www.rfc-editor.org/rfc/rfc2549

Latency and packet loss. And finches take less feed.

Man if there's one thing I can credit bell for, is that they really pushed for fiber. Before we had bell fibe here (for a shockingly reasonable price) in Montreal, we were stuck with absolute trash DOCSIS for so long. Every time the revisions increased ,the speeds would be nominally faster but in reality came with trash stability and peak time performance.

I'm sure DOCSIS is great for what it is, and in fact it's extremely impressive what it can do with existing cable lines, but the second biggest player here (Videotron) basically milked it dry. Again it's weird to praise them but Bell invested in wiring up the entire city and suburbs and I can get 3gbps symmetrical GPON FTTH for the price that 150mbps used to go for not even 3 years ago. I blame DOCSIS in a way because it made players with existing lines extremely complacent

Sewer are properly buried, Rogers cables are just thrown around with maybe a bit of dirt on top of it was a good day. I redid a wall in my backyard last year that is close to a Rogers box, I removed ~15 old cut cables from the ground.

I don't mean to boast, but on a good day, I get up to 4Mbps with Telekom. Welcome to the world of tomorrow!

There's also a follow up post that goes into a little bit more technical detail:

https://www.revk.uk/2017/12/please-upgrade-me-to-adsl-over-w...

Kind of by necessity the nature of ADSL, how else are you gonna offer broadband internet over the (by now) rotten infrastructure you were privatized into "owning". How can you squeeze as much profit (and as many bits per second) as humanly possible out of it, without ever investing a single cent more into your infrastructure than absolutely necessary? By relying on ever more absurd hacks.

Yeah, ADSL being so good at handling a crappy physical medium is both a blessing and a curse. If it weren't for these technologies we would have probably had to replace those rusty copper pairs decades ago for fiber optics. Instead the protocols continued to improve (ADSL2, ADSL2+, VDSL, VDSL2+, vectoring, supervector...) and allowed ISPs to provide usable network speeds without spending a cent on improving the infrastructure.

Copper thieves to the rescue!

Due to them, most ISPs in big cities in Brazil are switching to fiber to the home.

Mostly rural southern Chile got fiber before the coaxial-dependent capital because of the same problem.

You still need to bring fiber relatively close to the building, so it's not exactly happening without spending a cent.

Fun fact: Switzerland operates the only significant G.fast deployment in the world. The technology was such a flop that Huawei stopped making the hardware.

> Fun fact: Switzerland operates the only significant G.fast deployment in the world.

Nope. In Germany, M-net (Munich) and NetCologne operate massive g.fast networks, and if you don't want Huawei, go for Adtran's 516 lineup on the ISP side and AVM on the CPE side.

Zyxel and Fast Networks are also good on the ISP side (Not sure Fast Networks is still a thing - website seems to be down - but I run one of their DSLAMs and am happy with it)

When I still lived in Munich, I had M-Net since pretty much their inception. ADSL first, later fiber. It was always great, and on the very few occasions that I had problems, I usually directly got a technician on the line who knew exactly what they were doing, instead of a few layers of help desk peoples fielding calls.

My friends in Munich or the Ruhr region don't seem to know of any "massive" G.fast availability... which in any way is very late to the party. But I stand corrected.

I didn't know about network equipment from other manufacturers, not sure why we're stuck with Huawei here, but it's a dead end. The plan is to migrate as many G.fast subscribers as possible to FTTH in the next 5 years, and eventually to mmWave 5G in a few corner cases.

What about FTTC in Australia?

Has G.fast been deployed in significant numbers in Australia? I thought it was a few thousands subscribers only.

CenturyLink/Lumen has been using G.fast for most new FTTH deployments since 2016. They still install fiber to the outside of the house though, it's mostly about avoiding needing the installer to mess with wiring in the walls of existing houses, and being able to reverse power the outside node, instead of needing an outlet outside.

I'm pretty sure G.Fast was never actually deployed for NBN FTTC. It was planned/announced in 2021-2022, but eventually NBN came about their senses and decided to do FTTC -> FTTP upgrades like they're doing for FTTN.

I think that was an extremely small rollout. I didn't even know they ever deployed it until I checked when I read your comment. The upgrade path is full fibre, which you can now finally get in alot of places.

G.fast covers over a million premises in the UK. Extremely low take up partially as they started acceleration of FTTP build pretty much at the same time.

By the way most of the fibre needed to connect the FTTC/VDSL/GFast cabinets was already in the ground and they just needed to splice into it, as it was there for exchange to exchange backhaul, and leased lines. It's the final ~500 metres that's the expensive part of installing FTTP, as that has to be new and there is probably not a lead in duct that is clear so means climbing poles, clearing duct, or new trenching.

My home internet connection is VDSL2 and I see very consistent 100Mbps+ over the original phone cables of my house, which is built in 1933.

My wife and I have been looking for a property out in the rural parts of Michigan. One of the homes we went to visit with our realtor had left out a laptop computer in order to test the internet. Damn thing has ADSL and gets 2.2mbps down lmao. I do not miss the ADSL days.

>Damn thing has ADSL and gets 2.2mbps down lmao.

Had they considered an infrastructure upgrade to carrier pigeons, cans on a string, or smoke signals?

I started calculating the bandwidth for a continuous stream of carrier pigeons carrying 256GB flash drives, at different frequencies.

But the latency and loss rate would make it all worthless.

Latency definitely, but imagine pigeons carrying 8TB M.2 PCIe Gen-5 sticks strapped to their backs. That's some crazy throughput rivaling most domestic internet connections.

Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway.

https://www.reddit.com/r/vintagecomputing/comments/9of84w/ne...

Rings true for me. In my younger days I was "privileged" to catch an early morning flight to San Jose with a stack of tapes that I then drove to Palo Alto. All because a RAID array had gone kaput and tapes in a carry-on provided better bandwidth than the upstream from the office where our backups were.

My home used to get 4 Mbps down until water got into the paper insulated trunk lines and became unusable. My new pair maxxed out at 2. So happy that all my broadband internet surcharges were spent on improving the customer experience.

The Thumb area has been getting direct home fiber through a power company co-op. Been pretty great, I got mine like 6 months ago.

Before this we didn't even get DSL because the lines were so degraded.

I've been pleasantly surprised to see a lot of rural fiber from MEC - https://www.teammidwest.com/internet/

Actually serious question: Would this work as fallback tech in a war ridden zone? Not over wet string, but over something like reclaimed copper wire from whatever is around. Suppose laying fiber would be too risky and is too fragile, cannot be patched up in the field.

Fiber can be patched, but it take a lot more than just twisting the ends together like you can with copper. Usually they have a portable fusion splicer in case of a fiber cut and can at the very least fuse a length of fiber on each end of the break so it can pass light again.

I don't know what a fusion splicer is but I want one

The tool to make connections in fiber optic cables. They've got little handheld ones which are awesome.

https://www.fiberfoxamerica.com/fusion-splicer

Sounds like the type of thing one would borrow from Geordie Laforge.

I remember back around '98, there were a bunch of product that you could get that would turn the electrical wiring in your house into an ethernet network. You'd plug the thing in and then as long as the other end was on the same breaker, it would work great. I used it in my apartment to get network from one room to the other.

This reminds me of that.

Powerline adapters? They're fairly popular nowadays too, I've got four of them in my house.

Same… getting a decent connection too.

Yeah, I got some Devolo ones, they're pricy but they're bulletproof. I've never had to think about them once in the five years I've had them.

Home plug

ah i don't know. A 2023 (~cheap) car reverse camera for a videorecorder with (looking like) usb protocol on the wire between, does not work if cable is more than 5m. Or if it is another 5m cable (utp, ftp, 4x1mm, combination, whatever. Only that initial one). Period.

> Don't dare touch the string though...

Why not? Is it dangerous, ou would it just make it stop working?

The voltages used are very low, so it's more about adding impedance I'd say.

Literally and electrically impeding.

If it's also used as an analog phone line don't touch, if it's ringing you will get shocked

I guess if you are lucky, the added capacitance might rotate the impedance (on a smith chart) into a better range?

I guess it will rather disconnect the ADSL ;-)

This is why I get my internet from A&A, my wiring is pretty much this.

Way faster than dial up with a 56k modem.

That's how to get your internet to dry up.

Great experiment!

is this just a bot reposting old content?

Does it matter?

Almost certainly--judging by their submission timestamps, they appear to never sleep. I guess you can farm a lot of karma by just re-posting old popular posts.

Tony Finch is a real person: https://dotat.at/social.html

He used to be hostmaster@cam.ac.uk, amongst other things. Why he’s farming internet points on HN I’ve no idea!

A small world. I checked out his site and discovered I worked with his wife. He’s the Finch in Coleman Finch. Rachel is you are reading this, Hi! Hope you are well.

There are bots on HackerNews, 3 kind of them:

- Comments bots (like on other threads), usually to promote a crypto-thing.

- Submissions bots to farm karma (likely one of them here).

- Upvotes bots (taboo).

Recent karma is necessary for upvoting other posts, as there is a system which makes you can't upvote if you didn't get upvoted yourself.

If you can upvote some posts on HackerNews (as it would be on Reddit) you can help people make a lot of money, but again, you need recent karma.

Is that why I see so many comments that are just a paragraph or two pulled directly from TFA with no commentary or even indication that it's a quote?

Not entirely a bot and not entirely old content.

I’ve got a lot of good stuff in my link log https://dotat.at/:/ so I thought it might be fun to share a few retro classics. There has been some good discussion, so it seems to be worth it.

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