Electricians also almost always use the wrong colors when wiring speakers with something like a 16/4. I have ran into this a lot.
When I went to do low voltage later I realized what he meant. Stereo and security installations just isn’t something you want your electrician, whose knowledge mostly revolves around huge, 1000+ amp panels, to be doing. There’s way more money in commercial installs, so most electricians only do residential work to tide them over.
My dad doesn’t even want to terminate anything more complicated than 4 conductor phone wire, and would pull me into a job just for that reason.
What happens if you somewhat exceed the 100m limit? The only sources I can find boil down to just don't do that but I can't find a chart showing what happens to performance/frame loss.
Would it help to have a heavily shielded cable?
It depends on your system. If you're running old school shared medium Ethernet (with hubs, not switches, for cat5), or even just half-duplex mode, if your run length is too long, the big issue is that you've lost guarantees about collision detection; in that case, receivers may see collisions that senders don't, and you're left with transport layer resends (if any) instead of Ethernet layer resends. This is because of transmission speed, minimum packet lengths, and the length of the cable mean that one sender could finish transmission before seeing the second sender's preamble.
If you're running full-duplex dedicated medium, collision detection is a non-issue, there are no collisions. GigE transmits and receives on all four pairs simultaneously and uses echo cancellation to remove the echo'd send that comes back from the far end, the extra distance will make the echo come back later than expected, and that might be outside the ability of the network cards' signal processing to adjust.
Assuming that's not a problem, you would have more resistance, and probably more? capacitance, which may make signal recovery more challenging. 100BaseTx would probably be more likely to work than GigE, in my opinion, but I'd certainly try both. Ethernet autonegotiation runs on a single pair at 1Mbps, so it's quite possible that the cards will negotiate to 1G, and then not be able to actually communicate at that speed because of the wiring parameters.
One important thing to consider is that Ethernet wiring specifications are such that minimum standard wiring will work at a very low error rate at maximum length when in a bundle with many other ethernet cables/other low voltage signaling cables. If you don't have a lot of bundled cables, you have a bit more wiggle room. Of course, if you run the wires parallel and close to AC wires, you have a lot less wiggle room.
It would certainly make network engineers cry, but you have to work with the site and wiring you have, and only sometimes is it easy or convenient to run new cabling.
That is, at least, what was described to me in Computer Networks I back in 2006. I'm sure things have changed as we've moved to always using full-duplex wiring and fully-switched networks.
At work we had to repurpose a pair 170ish meter cat 6 cables for some cameras and it has worked nicely for three years (with PoE even). We tried again with a 100m cable rated for exterior (plus female + patch cords) and it wouldn't even link at 100mbps
The day came when it was time to test it out. All the Ethernet lights came on, but throughput was on the order of less than a few kbps. I let the project manager know that something was wrong with the cabling.
He got back to me a week later. The electrician who ran the line ran out mid way and used wire nuts to splice another length of cable. The fix was to simply terminate each end correctly on a splice connector. IIRC they might have even just re-ran one single length.
But the instinct not to trust electricians to run CAT5/6 was 101% correct!