Power line vs phone line LAN products
November 5, 2012 7:40 AM   Subscribe

Why are there many products for in-home power-line computer networking, but nearly nothing for phone-line networking?

Naively I would think that running a LAN over the phone wires that are already in my house would be ideal. Of course it would not be as good as CAT 5 arranged in a star topography with a switch in the middle. But the phone is already designed to carry data, and all the jacks on the same line already are electrically connected. I don't even have phone service in my apartment so I wouldn't even need to deal with "interference" from a phone. The phone line can already carry DSL, which is slow by today's standards but surely is more reliable than bad WiFi.

Or, you can run a LAN over power lines. People complain that performance varies depending on whether the sockets used are on the same phase or in the same circuit. Other possible interference sources include refrigerators, air conditioners, compact fluorescent bulbs, hair dryers--in other words, common things to plug into electrical sockets.

My searches revealed something called HomePNA, sort of the industry group to promote phone-line networks. But there are practically no products out there that actually do it. Meanwhile there are tons of power-line products, which some folks say work great and others say have problems.

So why are there so many power-line products but no phone line ones? Is the power line better for data than the phone line--seems odd to me, seeing as the phone line was actually intended to carry some data, no matter how slowly?
posted by massysett to Computers & Internet (7 answers total)
The typical home has power outlets in every room - often more than one. Phone sockets, not so much.

the phone is already designed to carry data

The phone wiring is designed to carry voice-grade analog audio, not data. The fact that DSL works at all is an absolute triumph of engineering.

DSL, which is slow by today's standards but surely is more reliable than bad WiFi.

802.11n WiFi is actually fairly easy to make not bad, and it's quite a lot faster than DSL.
posted by flabdablet at 7:50 AM on November 5, 2012

Power lines are good, thick copper. Phone lines, well... those are what's known as a Cat3 cable. If it's a good quality cable, it will run at 10mbps, wich is, today, three times slower than a typical cable modem connection. (Your house phone is not rigged to use 100B-T4).

Also, to get that 10mbps, you will need to disrupt phone communications over those lines. You and I may have cut the cord to the phone company, but most people have not. Those who have, need more oomph than a 10mbps connection between boxes. Wireless is much cheaper and faster.
posted by Slap*Happy at 7:53 AM on November 5, 2012

As flabdablet says, the typical home has many, many more power outlets - and as such, possible locations for network jacks with powerline networking - than phone jacks. But it's more than that: many types of computing hardware, from wireless access points to desktop computers, require both power and network connections. Many legacy phone jacks in older American homes are in locations where there is not also a power jack; they're up high on walls, or in alcoves, or just places where there aren't power jacks. That makes phone line networking a poor candidate for many applications; powerline gives you power and network in one location in virtually every room, while phone lines may not be present, or require you to run power from another location if they are.

While it's true that home phone line networking has typically been restricted to 10mbps, with only exotic 100mbps units that do not allow for telephone service to also be on the line, it is technically possible to run higher speed data over the line and maintain analog phone service; after all, ADSL2 can do 40mbps over phone lines over a limited distance. But given the broad applicability of powerline networking in typical homes, and the more limited applicability of phone line networking in those same homes, I don't believe there's much incentive for manufacturers to market those products.
posted by eschatfische at 8:05 AM on November 5, 2012

In university we set up our own LAN using arcnet which does in fact use phone cords instead of cat-5. It worked fine for us so there is that possibility, buy some arcnet cards (You still have an ISA slot right) and just use the existing phoe lines. You would need terminators and other nifty things that are a big pain in the ass, but we were able to play DOOM easily as well as connection share a couple of modems that were connected to the university 24-7. Oddly they didn't like it at the university and we had to take it down and next year there was a line in the student handbook about not being able to install your own network. The year after that you weren't allowed to install your own ceiling fans or tamper with the wiring in the dorm rooms (again after we had done just that).
posted by koolkat at 8:24 AM on November 5, 2012

Also think about coax networking. I have Verizon FIOS and it sends network over the home cable TV coax wires via a protocol called MoCA. There are inexpensive MoCA adapters available for purchase on Amazon and elsewhere that will give you a 100Kbps - 200Kbps network drop anywhere you have a cable TV connection in your home.

You may not need Verizon FIOS to use MoCA; you can just buy the plug and play adapter kit and start networking via coax.

Here is a good intro

posted by dudeman at 8:30 AM on November 5, 2012

There were a couple of folks who made phone-line networks. The HomePNA folks are the latest. Back in the day, Farallon made gear that could be used this way, though that was probably more for the Appletalk network (designed to be used on daisychained phone lines). Not sure were you are looking, but there seems to be a lot of people currently shipping HomePNA devices.

In theory, you could also use something like RS-485 if your end points supported it. There's some level of support for using IP over RS-485 in Linux; no idea about Windoz. That goes to about 1Mb/s, but usually much slower.

If you only want to connect two nodes together (like, a PC to the broadband router), you could pick up a pair of *DSL routers for not much and use that. Pairs of SHDSL modems come up on eBay regularly for small $. That gets you to 2.5Mb/s or so. You could even run T-1 over it.

As a followup to @dudeman, HomePNA 3.1 includes a standard for running IP over coax cable at up to 1Gb/s. Not sure if anyone is shipping product based on that yet.
posted by kjs3 at 9:36 AM on November 5, 2012

Unless you have some reason that your can't just fish a new wire (you rent, perhaps), that's the course I'd recommend over all make do options.

If you need real network speeds, and 802.11n isn't going to work, in my experience it's cheaper to just pull a new wire. We did this last year after spending years previous messing around with various other solutions including wireless, and powerline networking. I looked at cable (coax) and homePNA options as well. They all work to a degree, but the hardware necessary is actually very similar to the price of a cable pull and a pair of faceplates.

Call a local electrician. You might be surprised how cheap getting real Cat-6 installed is.
posted by bonehead at 10:27 AM on November 5, 2012

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