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Author Topic: Ethernet over coaxial?  (Read 4655 times)

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Offline Floid

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Re: Ethernet over coaxial?
« on: April 05, 2003, 02:32:19 AM »
"Run one pair" to the coax?  Huh?

Anyhow, hubs with a 10base2 'uplink' can be found from PCBay.  Note that those are FCC Class A, meaning "they could use some shielding" ;) -  using them at home did give cause me a little localized TVI that I really should've done something about.  (A little bit of patterning on off-air channel 5, with the coax run ungrounded and strung close to the antenna.  Probably nothing that'd bother neighbors.)

If your network card has an AUI connector (DB15), you can find an external transceiver cheap on eBay.  Search for "thinnet transceiver," "10base2 transceiver," etc.  You might also find a more bulletproof hub.

If your card doesn't have an AUI or BNC connector, and we're talking x86-land here, it's cheapest to just find one that does.  I like old ISA cards based on the Realtek 8019(AS?), which is about as high-performance as an NE2000 clone gets.

You can also scrounge true plug'n'play UTP <-> 10base2 bridges/repeaters on eBay.

If you're thinking about recycling television wiring as 10base2- no, it's not the same stuff, but you can sneak by if you're not concerned about potentially sacrificing your cards/hubs.  Here's a newsgroup thread on the topic, and another post by someone suggesting a termination technique.  I wouldn't risk any rare-classic-Amiga-hardware to such a setup, but with two Ark/Noname hubs on each end, it's a possibility.

Other neat ethernet tricks include recycling unused phone pairs for 10baseT, as I said elsewhere (presumes your location was wired with decent-quality CAT3 cable), and then there's HomePNA and HomePlug and wireless to choose from...
 

Offline Floid

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Re: Ethernet over coaxial?
« Reply #1 on: April 06, 2003, 05:00:31 AM »
Quote

redrumloa wrote:
Thanks for all the responses! I am going to be upgrading an arcnet network to ethernet and using the existing coaxial would be the easiest route.

Anyone know off the top of their head what flavour coxial arcnet uses?


RG-62, with an impedance of 92 ohms.
Which feels like a bit of a stretch for 10base2.  If you're dealing with a home or extreme-SOHO setup, you could see how things fare with 50 ohm terminators and the aforementioned disposable hubs, but if this is anything 'real' - meaning intended to be relied on at all - you'll need to find some true media converters, which probably won't come cheap.  (Google's not being helpful for me tonight.)

I find one reference to Windows offering Ethernet-over-Arcnet encapsulation, a trick that could probably be performed by Linux or *BSD as well... that'd imply sticking with the existing Arcnet, and plopping tunnel endpoints on each end.  This would, of course, leave you stuck with Arcnet and its speed limitations, but at least you'd know you're in-spec and shouldn't need to plan for replacing impedance-mismatch-torched hardware.

Here's one hit for some more-appropriate hardware:
USENet thread mentioning media conversion hardware..
Be sure to read down to the next message, which elaborates on the 'unbaluns' that could be used as well.

Sounds like, if you've got a building/campus full of the stuff, you want to track down a bunch of the mentioned RG-62-capable hubs.  If it's just one point-to-point link, you might get by "reliably" with the cheapo Ark hardware, *and*  appropriate 'unbaluns.'  Or, if we're talking a whole building here, and tracking down enough of the RG-62-capable hubs is trouble, an all-10base2 hub/switch, *and* enough of those unbaluns for both ends, allowing one of the cheapo Ark hubs (or a machine with a 10base2 NIC) to be placed at each drop.

When you get to that last point, just about any alternative- pulling CAT5, deploying wireless, buying a few overpriced HomePNA bridges and recycling existing phoneline- starts to sound good.
 

Offline Floid

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Re: Ethernet over coaxial?
« Reply #2 on: April 06, 2003, 05:05:04 AM »
I did find one Google hit for the 'unbaluns.'  You'd have to order from Germany, but maybe it's still cheaper/saner than other possibilities for your application.

Edit: ...and note that you need a true "media converter" (or a hub) to go between 10baseT and 10base2.  You might come across 'dumb' baluns that can use UTP as the equivalent of coax for 10base2 networks, but they can't magically turn the differential signals of 10baseT into a signal that can travel over coax.  (I don't know where you or anyone else is coming from in this thread, so... as a basic identification metric: if it has blinkenlights and/or requires power, it's not 'just a balun.'  If it doesn't require power, it probably is.)
 

Offline Floid

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Re: Ethernet over coaxial?
« Reply #3 on: April 08, 2003, 11:45:44 AM »
Quote

Desmon wrote:
@redrumloa
If the project really is that critical, then replacing all the Arcnet cable with thin ethernet coax is gunna get to be more costly than replacing it with Cat5 AND supplying ethernet cards to all the machines.


Agreed, only again noting the special case of those 'unbaluns.'  Those are pretty simple (ie: shouldn't be failure-prone) gadgets, so if the coax is in good shape, it might still be economical- if you can just find a source for enough, with enough spares just-in-case, which seems to be the hard part.

Then there's the matter of what you put at the 'top' of the network- AFAIK, industrial-strength switches can (still) be had with all 10base2 cards (though this is more of a "call Cisco" issue than a "go to CompUSA" one) - and at the edges, going with the dirt-cheap Arks I mentioned will only give shared, not switched, ethernet among their ports at each drop, so it depends what each drop will be serving.  You could always plug a cheapo 10/100 switch into each hub (or just use media converters, but the Ark hubs make cheaper media converters than the media converters), if it makes sense (e.g., if most drops serve one office, and that office's computers will mostly talk to themselves anyway)...

Running a spreadsheet on costs of hardware vs. costs of labor to pull cable would be a good idea, if this is an option.

Quote

One other advantage is that the Cat5 can be run to a central switch (or hub if you prefer) without all the hassles of a peer 2 peer network.


ArcNet is a star topology, even on coax, so all his runs are heading back to central point(s).  However, you'll never break 10mbit on coax with ethernet, so it's also a question of what the facility is meant to be used for, meant to be future-proofed against, etc.  (You could, of course, tie various 'workgroup'ish areas at the switch end, linking various 10mbit networks with 100mbit switches, routers, etc...)

If they survived on ArcNet until now, one has to wonder about their bandwidth needs.  OTOH, any 'normal' contractor would just come in, shrug, and send guys around fishing CAT5 or fiber (MCSEs because "That's what you need for computers!" and UNIX guys because they know you'll need the bandwidth *someday* ;)), so it's all about the cost-benefit work.

Questions to ask yourself are, obviously- Is this an organizational network (e.g., workgroups, backups, etc?), or "just" a way to get internet to a lot of people? - How cheap is wireless going to be/is it an option for the facility/5 years down the line? - Any RFI issues (welding machines, medical equipment) that make fiber look really good? - How long *are* these runs? - Does anyone want centralized backups/massively centralized file storage/anything else that'll saturate even 100mbit for minutes at a time?

Stupid thought- If these are *really* long (>200m, is it?) runs, maybe some of the cable-modem DOCSIS stuff is something to look into... (Google for "CMTS" and similar.)  You'd (still) need (different- 93->75 ohm) unbaluns, for that case, a handy knowledge of RF/CATV to install it, and appropriate modems for the edges, but it might be a way to get 'modern' speeds without changing the whole cable plant.  May also survive ArcNet 'passive hubs.'

Sorry for the disorganized response; just trying to raise even more issues to worry about.  Just hanging around the building my father's office was in, I saw all sorts of goofy stuff- one floor with some law offices wired for 100mbit, at much cost, only to dangle a Linksys router off of.. and  down the stairs, the booking/IT department for a travel agency, filling the dumpster with cable every dozen months  as they went from generic UTP to CAT3, CAT3 to CAT5, CAT5 to 5e...  The moral is, plan!  (And if recycling the coax is fractional to the cost of rewiring the place, you could always do it just to see what the usage will really look like, before commiting to any new topologies.)

Edit:  Oh yeah, and @redrumloa- No problem, and good luck! ;)