The hub was built to emulate the behavior of 10base2 and 10base5. 10base5 was the original inch-thick coax, and adaptors actually drilled into the cable. I hav

The hub was built to emulate the behavior of 10base2 and 10base5. 10base5 was the original inch-thick coax, and adaptors actually drilled into the cable. I have found 10base5 taps in odd places over the decades of my career. 10base2 was coax cable that we recognize, and there were t-connectors that allowed two cables to link into a host's network adapter. The ends of the cable were capped with resistors ("terminators") that would radiate network traffic into (a very small amount of) heat. This model uses CSMA/CD (carrier sense mutiple access/collision detect) very literally. Any station could transmit at any time, up to a maximum of 1518 bytes, including the Ethernet frame header. Transmit collisions were detected as frame size overruns. If the cable were too long, the ends would see correct transmissions, but the middle would see collisions. This explains the 500 and 200 meter limits of 10base5 and 10base2. An understanding of this original topology and its limits is informative in the reasoning for modern Ethernet.