Editing Ethernet (section)

===Repeaters and hubs===
[[Image:Network card.jpg|thumb|A 1990s [[Industry Standard Architecture|ISA]] [[network interface card]] supporting both coaxial-cable-based [[10BASE2]] ([[BNC connector]], left) and twisted-pair-based [[10BASE-T]] ([[8P8C]] connector, right)]]
{{Main|Ethernet hub}}

For signal degradation and timing reasons, coaxial [[Ethernet segment]]s have a restricted size.<ref>{{Cite web|url=https://kb.wisc.edu/ns/page.php?id=7829|title=Ethernet Media Standards and Distances|website=kb.wisc.edu|access-date=October 10, 2017|archive-date=June 19, 2010|archive-url=https://web.archive.org/web/20100619010200/https://kb.wisc.edu/ns/page.php?id=7829|url-status=live}}</ref> Somewhat larger networks can be built by using an [[Ethernet repeater]]. Early repeaters had only two ports, allowing, at most, a doubling of network size. Once repeaters with more than two ports became available, it was possible to wire the network in a [[star topology]]. Early experiments with star topologies (called ''Fibernet'') using [[optical fiber]] were published by 1978.<ref>{{cite journal |title= Fibemet: Multimode Optical Fibers for Local Computer Networks |author1= Eric G. Rawson |author2= Robert M. Metcalfe |journal= IEEE Transactions on Communications |date= July 1978 |volume= 26 |issue= 7 |pages= 983–990 |url= http://ethernethistory.typepad.com/papers/Fibernet.pdf |doi= 10.1109/TCOM.1978.1094189 |access-date= June 11, 2011 |archive-date= August 15, 2011 |archive-url= https://web.archive.org/web/20110815204821/http://ethernethistory.typepad.com/papers/Fibernet.pdf |url-status= live }}</ref>

Shared cable Ethernet is always hard to install in offices because its bus topology is in conflict with the star topology cable plans designed into buildings for telephony. Modifying Ethernet to conform to twisted-pair telephone wiring already installed in commercial buildings provided another opportunity to lower costs, expand the installed base, and leverage building design, and, thus, twisted-pair Ethernet was the next logical development in the mid-1980s.

Ethernet on unshielded twisted-pair cables (UTP) began with [[StarLAN]] at 1&nbsp;Mbit/s in the mid-1980s. In 1987 [[SynOptics]] introduced the first twisted-pair Ethernet at 10&nbsp;Mbit/s in a star-wired cabling topology with a central hub, later called [[LattisNet]].<ref name=VonBurg2003 /><ref name="Spurgeon 2000"/>{{rp|29}}<ref>{{cite book| title = The Triumph of Ethernet: technological communities and the battle for the LAN standard| author = Urs von Burg| publisher = Stanford University Press| year = 2001| url = https://books.google.com/books?id=ooBqdIXIqbwC&pg=PA175| isbn = 0-8047-4094-1| page = 175| access-date = September 23, 2016| archive-date = January 9, 2017| archive-url = https://web.archive.org/web/20170109135141/https://books.google.com/books?id=ooBqdIXIqbwC&pg=PA175| url-status = live}}</ref> These evolved into 10BASE-T, which was designed for point-to-point links only, and all termination was built into the device. This changed repeaters from a specialist device used at the center of large networks to a device that every twisted pair-based network with more than two machines had to use. The tree structure that resulted from this made Ethernet networks easier to maintain by preventing most faults with one peer or its associated cable from affecting other devices on the network.{{citation needed|date=April 2020|reason=OK, repeaters are required to deactivate ports that send excessive collisions, such as due to internal defects, or external wiring defects. That is an important part of this statement.}}

Despite the physical star topology and the presence of separate transmit and receive channels in the twisted pair and fiber media, repeater-based Ethernet networks still use half-duplex and CSMA/CD, with only minimal activity by the repeater, primarily generation of the [[jam signal]] in dealing with packet collisions. Every packet is sent to every other port on the repeater, so bandwidth and security problems are not addressed. The total throughput of the repeater is limited to that of a single link, and all links must operate at the same speed.<ref name="Spurgeon 2000"/>{{rp|278}}