brown@lincoln.ac.nz (12/19/90)
Does anyone know why Digital allows only 2 repeaters in the signal path between any two stations on the network, whereas the 802.3 standard allows 4 repeaters between any two stations ? The reason I ask is that we are considering buying a fibre optic hub device. Digital's Chipcom device is repeaterless but expensive, while the competition's Isolan EtherConnect hub is classed as a repeater but is cheaper. We have a thickwire ethernet network with DEMPRs off it, and propose connecting the hub to this via a bridge. Out of the hub, fibre would run to several new locations on campus, with DELNI/DEMPR at the end of the fibre in order to run thinwire ethernet within buildings. Is anyone out there using an Isolan EtherConnect hub with fibre line card in this configuration ? What are your experiences ? With thanks in advance, Martyn Brown, Centre for Computing and Biometrics, Lincoln University, N.Z. Internet : m.brown@lincoln.ac.nz Bitnet : m.brown%lincoln.ac.nz@relay.cs.net Fax : (64)(3)252944
koning@koning.enet.dec.com (Paul Koning) (12/19/90)
|> |>Does anyone know why Digital allows only 2 repeaters in the signal path between |>any two stations on the network, whereas the 802.3 standard allows 4 repeaters |>between any two stations ? Both allow the same thing. The difference is ONLY in the way it is described: the DEC/Intel/Xerox "blue book" uses one set of terminology, the 802.3 standard a different one. In the blue book, "repeater" is something with connections to the coax (or equivalent) on each side. Something that connects to a fiber point to point link is a "half-repeater". The rules allow 2 repeaters, where each repeater can be replaced by a pair of half-repeaters. In the 802.3 standard, both "repeater" and "half-repeater" are called "repeater set". It says you can have up to 4 of these, but IN ADDITION adds the rule that out of the 5 resulting segments, only 3 can be coax segments. The remaining ones must be link segments. If you translate this into blue book terms, you will conclude that you can have either two repeaters ("2 repeater sets, 3 coax segments, 0 link segments"), or one repeater and two half-repeaters ("3 repeater sets, 3 coax segments, 1 link segment") or four half-repeaters ("4 repeater sets, 3 coax segments, 2 link segments"). So while this unfortunate terminology change makes the words different, there IS NO DIFFERENCE in the topologies that are permitted. paul