Running Ethernet over existing coaxial cable

https://til.simonwillison.net/networking/ethernet-over-coaxial-cable

by finallyy • 2 years ago

45 63 2 years ago

til.simonwillison.net

dmw_ng2• 2 years ago

AIUI the minimum latency on these is always measured in milliseconds, with 6-7ms apparently commonplace, which you're going to immediately feel using e.g. a block or network storage protocol. No references, but did look at moca for exactly the same reason a few months back. The physical size of the models I looked at also suggested you'd want to check power consumption before stuffing a home full of them - custom devices in a small market segment often drink electric.

I'd much prefer a consistent <1ms latency 10 Mbit connection than 10ish ms gigabit with 100ms spikes when next door boils their kettle, etc.

godman_8• 2 years ago

If you’re not using any splitters and zero to a few couplers you can expect latency to be ~3ms with the model OP is using. You can easily achieve 1Gbps using NFS with 3-10ms of latency as long as the underlying hardware can support it. I would avoid doing block storage even over ethernet though, that should be reserved for DAC or fiber. These particular adapters are rated for 10W (5V/2A) and I doubt they use all of that. I haven’t seen any noticeable latency spikes using these either but your mileage will vary depending on your cabling and connections (especially older pre-digital cable splitters.)

Schnitz• 2 years ago

Moca is a fantastic option if you have a good quality coax run, ideally point to point without splitters. For example a lot of people at some point pulled coax from wherever the cable enters the house to their living room. Now when you get fiber, the fiber probably enters the house in the same spot as the coax does. You can repurpose the coax run to keep your media center hardwired, as a wifi backhaul, etc. and in those use cases (streaming, wifi, etc) the additional 5ms of latency are IMHO irrelevant. Of course, if you can run a new cable with ease, nothing will beat high quality Cat 6. A lot of us just don't have that options, lack of crawl space or attic, etc.

runjake• 2 years ago

I have the same set of ScreenBeam MoCA adapters that are in the article and I get <=1ms. I do not have any other signal on the coax run I'm using.

Most home users aren't going to really notice or care about a 6-7ms latency for even network file protocols. They're probably using Wi-Fi anyway.

mdasen• 2 years ago

The average latency for MoCA 2 devices is 3.5ms which is half what you say the "minimum latency" is. The latency on my WiFi averages 7ms. So it's likely going to be better than a WiFi connection.

My MoCA devices don't use crazy amounts of electricity either.

It could also depend on where you are. In the US, homes often have quite good coax wiring. That might not be the case in many parts of the world.

I'd much prefer a consistent <1ms latency 10 Mbit connection than 10ish ms gigabit with 100ms spikes when next door boils their kettle, etc.

Honestly, this just feels like FUD. You've made up a scenario with latency numbers that are wrong claiming with zero support or evidence that a neighbor boiling their kettle will make a connection bad. It sounds like you briefly looked at MoCA, never tried it, but formed a very strong opinion about it based on basically nothing.

dmw_ng2• 2 years ago

but formed a very strong opinion about it based on basically nothing.

3.5 ms is between 5x - 53x worse than what you'd see out of gigabit ethernet, depending on the quality of the equipment, but even at the low end this is absolutely something noticeable in any application heavy on round-trips (such as those mentioned). Nothing breaks my focus more quickly than an unpredictably slow or janky UI, it is far from a made up scenario, just open an explorer window pointing at an SMB share with a few hundred JPEGs with uncached thumbnails and you've already hit it. I'd much prefer consistency of a slower network than usability that evaporates at random, else what is the point of preferring a wired network over wireless in the first place?

FWIW, listing a directory or opening a single file over SMB is at least 4 round-trips, that's 14 ms burned on lag just for a single thumbnail, in the best case, and it only multiplies from there.

thehappypm• 2 years ago

Umm, what? MoCa devices are very small and use negligible power. They also introduce far less latency than WiFi.

core-utility• 2 years ago

I have these to get wired connection from my rack to my home office, to add in a WAP and wire my desk computers. They've worked solidly and I get great throughput. I'm not a gamer so I can't speak to latency but I'd imagine if the tradeoff was this or wifi, this would still be a more desirable option.

I'm self-limited to 1G because what supports 2.5G these days? Not my equipment.

PlutoIsAPlanet4• 2 years ago

I have tried MOCA, but it runs at higher frequencies than cheap European coaxial was designed for (lower frequencies for terrestrial television) and had stability/performance issues due to this.

There's an alternative called G.hn over Coaxial, that runs at 100-200Mhz which seems to fair much better on crappy coaxial, at the cost of max bandwidth (500Mbps-1000Mbps) and harder to get hardware.

The manufactures of G.hn2 Coaxial adapters seem to be stingy about selling them to individuals.

sidewndr463• 2 years ago

Given that WiFi is meant to work over the air, you could probably get a set of access points, RP-SMA to type-F adapters, and a set of attenuators and connect them back to back over basically any random coax. The loss is higher in the coax than in the air but there should be a noise floor consistent with transistor noise at room temperature.

You'd want to start with as many pads as possible, so something like >80 dB of pad. Remove them one on by one until the reported signal level is in the middle of the acceptable range.

From the device perspective it won't really know the difference. You might need to disable antenna diversity as otherwise the APs might attempt to use one of the antenna ports with nothing connected to it.

Dylan168074• 2 years ago

The loss is higher in the coax than in the air

Oh, I did the math on this before.

So you technically don't have much loss from the air itself, but you lose 6 decibels every time you double the distance from the antenna. So at the distances people normally use wifi, the loss from distance alone is higher for air than for coax. And that's not counting the 40+ decibels of loss you start with for adjacent devices with antennas.

ssl-35• 2 years ago

Wifi radios are generally designed for 50 Ohm impedances.

But household TV coax in the States (RG-59, RG-6, RG-11, and friends) is 75 Ohm.

And impedance matters. How much it matters varies by application, but it can be very important. There's more going on in bit of coax than a shielded conductor[1]. (Relatedly, twisted pair cabling like Cat5e has more going on than a few pairs of wires that happen to be twisted.)

But the concept of having a pair of radios connected together with coax does, of course, work fine as long as the I's are crossed and the T's are dotted. I've set up PtP Wifi-ish wireless links on the bench with attenuators and coax jumpers instead of antennas, but I kept the characteristic impedance consistent throughout. (Many-to-many networks are also possible, with similar caveats.)

[1]: Similarities of Wave Behavior, as presented by Dr. J.N. Shive, 1959. https://www.youtube.com/watch?v=DovunOxlY1k

shellfishgene• 2 years ago

The manufactures of G.hn2 Coaxial adapters seem to be stingy about selling them to individuals.

I can find several at Amazon (Germany). For example https://www.amazon.de/GIGA-Copper-Ethernet-Netzwerk-Koaxialk...

PlutoIsAPlanet4• 2 years ago

I wanted to grab a pair of Nexuslink/Comtrend adapters.

mrkstu• 2 years ago

I have ancient coax in the US on my house built in the 70s, leading to syncing at lower bandwidth often on my moca, sometimes as low as 100Mb. Luckily it runs outside the house, so at some point I’ll replace it with newer cable and actually get the theoretical 2.5 Gb.

Symbiote• 2 years ago

If you're replacing the cable, you may as well install an ethernet cable.

PlutoIsAPlanet4• 2 years ago

I would suggest trying G.hn over MOCA on old coax networks.

When I tried MOCA, disabling the upper frequencies on the devices would lead to a much stable performance, at the cost of speed. MOCA seems designed with cable networks in mind.

G.hn had no issues, and the latency is much lower than Moca (1-2ms vs 6ms).

jauntywundrkind• 2 years ago

G.hn also is available as a power line technology too.

I'd used HomePlug powerline for years in various houses/apartments. Some links would be 150Mb/s, others struggled to keep 20Mb/s, depending.

I had high hopes G.hn2 was going to be a lot better, but both Nexuslink & Comtrend 2Gb/s failed to make a significant difference for me versus the HomePlug, still usually under 40Mb/s. That house had particularly bad wiring it seems.

Dedicated coax could be way better. Interesting to hear a moca failed story! I didn't consider that as a possibility.

PlutoIsAPlanet4• 2 years ago

I'm in the UK where powerline doesn't fair well agaisnt the UKs ring circuit style electrical networks.

zcw1002• 2 years ago

There’s something even better than MOCA. Black electrical tape. You tape the cat5 to the end of the coax and then pull really hard and then you get great performance.

franga2000• 2 years ago

If the cables were run in conduits AND if there aren't any sharp turns AND if you own the place or got your landlord's permission.

zcw1002• 2 years ago

Yes. All true. I just hate the coax in my house. It pisses me off every time I see there they installed it by just drilling a hole in the facade.

Spivak• 2 years ago

I will eat my hat if anyone installing coax actually uses conduits, the kind of people doing the installation -- your cable provider gives zero shits. Avoiding "sharp turns" should be no issue since in your average home you're not gonna need >4 quarter turns that would necessitate a junction box.

sidewndr463• 2 years ago

I did the same thing but actually pulled the original coax back through as well. It's just like a permanent pull cord now. The stuff is too small to be useful for anything anyways, might as well live out the rest of its life sitting in a wall cavity.

tguvot5• 2 years ago

i believe, in usa, according to building code wires should be stapled to studs (if wiring done during construction). i tried to pull out one stapled wire, it didn't really work

ssl-35• 2 years ago

There aren't any universally-adopted residential building codes in the US. (Things like the National Electric Code and Universal Plumbing Code simply aren't at all what their titles may appear to suggest.)

gkfasdfasdf• 2 years ago

If cables are running through holes drilled through studs/joists those may be filled with flame-retardant foam, which could make pulling tricky.

xenadu02• 2 years ago

There are also PoE over Coax devices if your house (like mine) was setup with NTSC security cameras: https://www.amazon.com/gp/product/B07G194BQD

This device picks up PoE power and ethernet at one end and delivers up to 21w at 100m to the remote end (less for longer runs). Enough to run most IP cameras. Speed is only 100Mbps (up to 300m, 10Mbps at 1000m) but that's more than enough for 4k live streaming.

It also supports transmission over twisted pair instead of coax. You can use that to pipe Ethernet and PoE over twisted pair doorbell or phone wire. Apparently a common usage is getting Ethernet onto older elevators over the legacy twisted pair emergency phone line. How much bandwidth and power you get depends on the quality and type of wire - in my experience it does a decent job adapting to conditions.

Dylan168074• 2 years ago

I bet there was something physically wrong with the cat5 wiring as the actual reason it couldn't do gigabit.

Libcat99• 2 years ago

Regular cat5 is only rated at 100mbit.

5e will handle gigabit, and I've seen 5 work for short runs too.

Dylan168074• 2 years ago

5e will not just handle gigabit, it's enough to run 2.5gig at spec to 100 meters.

5 has the same bandwidth as 5e but allows more crosstalk. And gigabit is intended to work on cat5. If gigabit is not working on cat5 cables <50m, I put my money on there being something wrong with the hardware/install in that house.

dboreham• 2 years ago

GigE works totally fine on bog standard 25 year old Cat5 over 100s of ft.

toast0• 2 years ago

The spec for older ethernet standards is with 100 meters of cabling with most of it un dense conduit. You can get away with lesser cable when runs are shorter and not in dense conduit. I had a run of mixed cat5e and cat3 that did gigE just fine. I'm not sure I've ever seen actual cat5 in the wild, but from what I've heard, most cat5 will test to cat5e spec too.

I have 10g-base-t running reliably on cat5e as well. (30ish meters)

riehwvfbk• 2 years ago

Was going to post the same thing. I had a new construction townhouse in the Bay Area that had Ethernet. The max speed was either 10 or 100 Mbps depending on which jack was used. Opened up the jacks to discover that the cables were stripped of the jacket for at least 6 inches, the twisted pairs were untwisted and this mess was jammed into the wall behind the jack. At every single location. The worst offender wouldn't connect at all. That had a foot of jacket stripped off. Re-crimping all the jacks made everything work at 1 gigabit.

In summary, general tradespeople don't know how to install Ethernet.

justsomehnguy• 2 years ago

My best anecdote on that is when an Ethernet wallplug was punched down with a flat screwdriver... which worked as hardware firewall for the SMB traffic. Everything else worked fine: ICMP, HTTP/S... but not SMB. After I re-punched it with a proner Krone it started work fine for the SMB traffic just fine.

antisthenes• 2 years ago

Yep, I had a cable that was working at gigabit, until it was pinched by a door and bent really hard. Then it started working at 100 MBPS.

icedchai• 2 years ago

It probably only has 4 wires hooked up. That's all you need for 100 meg.

Despite claims to the contrary, gigabit will work over cat 5 (just not 5e!) in the majority of cases.

johnklos• 2 years ago

Cat 5 is more than adequate to do gigabit for even huge houses.

If some conductors aren't connected, have bad connections, or the order of wires is wrong, then many gigabit ports will negotiate to 100 Mbps, which only requires four working wires out of the eight.

A cable tester from Micro Center (if you're lucky enough to have one close enough to visit) is $7.99, plus a 9 volt battery (which, funnily, is about half the price of the cable tester). Amazon has the same testers for around $10.

MoCA is great, particularly if you're using cable boxes that require Internet over MoCA and you want to replace the NAT router your ISP provides, but it's a bit silly to use MoCA when you have wires that probably just need to be re-terminated or terminated properly.

khaki54• 2 years ago

I have these in my house. They work super good, and I usually plug them in to a switch that can do 2.5Gb and then from there any media devices or AP. What's interesting is they are not point to point, they're like a bus topology or something. You can have 5 and they will all work fine.

lostmsu• 2 years ago

What models?

superkuh• 2 years ago

RF IF modulation will always be more spectrally efficient than baseband modulation all things held equal. Especially at the low end of the DC->whatever range. RF is just more computationally/electrically expensive.

hughesjj2• 2 years ago

Funny, literally just bought one of these for an htpc in a noisy wifi environment with a cable run but no Ethernet

flenserboy• 2 years ago

Just got some MoCA adapters, & they've been great. Not quite gigabit speed, but the ones I got only go to 1 or 2.5 if there are only two, while we have three in place. It's made the whole house much more usable — older houses & WiFi don't always mix. If there's a run already in place, it's definitely worth trying out.

Aloha• 2 years ago

I put Coax and Ethernet all over my house with the idea of doing MoCA or whatever else I could with it - right now its feeding an FM Modulator into my coax system.

kps2• 2 years ago

Sorely disappointed this wasn't about 10base5.

zh3• 2 years ago

No mention of frozen garden hose in the title should have given it away.

kps2• 2 years ago

I still have a few vampire taps in a box in the basement, but no cable. (Anyone need spares?)

yjftsjthsd-h• 2 years ago

Yeah, my first thought was also along the lines of "well yeah that's just ethernet"; I figured somebody hit a use case where the older physical wiring was easier to use:)

cyrialize• 2 years ago

My old apartment had coax cables in the office I used. My old apartment was also an old home with a TON of interference, making WiFi travel terribly.

I did my research, bought moca adapters, and set everything up. As it turned out, the coax cables upstairs in the office... weren't plugged into anything.

I ended up just buying a flat ethernet cable and 3m strips. I put it all around the trim and both my wife and I are pretty short - so no one ever saw it. It went to a POE AP in the office.

I now own an old home. I was excited to see a bunch of coax outside, but alas, previous homeowners have either pulled out all the old coax or snipped it. There still are old holes everywhere from the coax - so hopefully one day I'll be able to snake an ethernet cable through and get an AP up.

orev• 2 years ago

MoCa is great, but I don’t see a mention of using a point of entry filter to make sure your local network doesn’t leak out into the rest of the neighborhood. I’m surprised that kit didn’t come with one.

Running Ethernet over existing coaxial cable

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