5 ms·

Semi-off-topic Q: Why did twisted pair cables become the standard for ethernet? Seems to me from a signal integrity standpoint that coaxial (yes, there was "thi

by jabl 8y ago

Semi-off-topic Q: Why did twisted pair cables become the standard for ethernet? Seems to me from a signal integrity standpoint that coaxial (yes, there was "thin" and "thick" ethernet back in the day) or twinax type cables would be much better? Were they originally cheaper than coax, or what is the reason?

eyeareque 8y ago
Briefly, twisted pairs reduce noice and crosstalk.
alanfranzoni 8y ago
IIRC coaxial was terrible back then. It was stiffer and hence harder to place around corners, and the connectors were harder to clip on. I don't know if those reasons were important or even considered, back then.
avian 8y ago
Cost and simplicity of installation. Twisted pairs and crimp-on RJ connectors were already widespread in telecom due to POTS. If not for anything else, they were cheap and their reliability well understood due to economies of scale. On the other hand, coax cable was significantly more expensive per length. Compared to RJ, BNC coax connectors were expensive and hard to correctly crimp onto the cable. When computer industry tried to make them cheaper it also resulted in very crappy products. Unreliable connections were cause of most of the gripe with older coax-based networks. Which is kind of counter intuitive. A properly made BNC is very reliable and still used extensively in electronics test equipment and RF applications. But apparently reliability just didn't scale down cost-wise.
- flyinghamster 8y ago
  I also don't miss the daisy-chain wiring of coax Ethernet. Any one connector getting out of whack, or a bad/missing terminator on either end, would take the whole network down.
  - ansible 8y ago
    And adding a new drop with coax meant taking down the entire network temporarily.
  - avian 8y ago
    Yes, but network topology is orthogonal to the type of cable used. We could have just as well used coax for modern switched connections.
    - chrisdhoover 8y ago
      We did star configure CCTV systems using RG59 and RG6. The cables are heavy and the connectors big. You can't get the same density as with UTP. A 48 port coax switch took 4U versus a 1U UTP switch
duncans 8y ago
In the 90s I worked for a small company whose LAN was Ethernet over coax. The main issue was if there was a dodgy BNC connector/splitter or break in the cable anywhere in the building, the whole LAN would go down, which was fun to track down. When hubs and switches became cheaper and twisted pair (10BASE-T) more common we migrated over.
- jabl 8y ago
  Yeah, for ethernet the switch from coax to twisted pair coincided with the switch to a star topology. That topology change was good for a lot of reasons. When asking this question, I was more interested in learning about the signaling issues in the different cable types.

by jabl 8y ago

eyeareque 8y ago

Briefly, twisted pairs reduce noice and crosstalk.

alanfranzoni 8y ago

IIRC coaxial was terrible back then. It was stiffer and hence harder to place around corners, and the connectors were harder to clip on. I don't know if those reasons were important or even considered, back then.

avian 8y ago

Cost and simplicity of installation. Twisted pairs and crimp-on RJ connectors were already widespread in telecom due to POTS. If not for anything else, they were cheap and their reliability well understood due to economies of scale. On the other hand, coax cable was significantly more expensive per length. Compared to RJ, BNC coax connectors were expensive and hard to correctly crimp onto the cable. When computer industry tried to make them cheaper it also resulted in very crappy products. Unreliable connections were cause of most of the gripe with older coax-based networks. Which is kind of counter intuitive. A properly made BNC is very reliable and still used extensively in electronics test equipment and RF applications. But apparently reliability just didn't scale down cost-wise.

flyinghamster 8y ago
I also don't miss the daisy-chain wiring of coax Ethernet. Any one connector getting out of whack, or a bad/missing terminator on either end, would take the whole network down.
- ansible 8y ago
  And adding a new drop with coax meant taking down the entire network temporarily.
- avian 8y ago
  Yes, but network topology is orthogonal to the type of cable used. We could have just as well used coax for modern switched connections.
  - chrisdhoover 8y ago
    We did star configure CCTV systems using RG59 and RG6. The cables are heavy and the connectors big. You can't get the same density as with UTP. A 48 port coax switch took 4U versus a 1U UTP switch

duncans 8y ago

In the 90s I worked for a small company whose LAN was Ethernet over coax. The main issue was if there was a dodgy BNC connector/splitter or break in the cable anywhere in the building, the whole LAN would go down, which was fun to track down. When hubs and switches became cheaper and twisted pair (10BASE-T) more common we migrated over.

jabl 8y ago
Yeah, for ethernet the switch from coax to twisted pair coincided with the switch to a star topology. That topology change was good for a lot of reasons. When asking this question, I was more interested in learning about the signaling issues in the different cable types.