On Wed, Jun 27, 2018 at 10:59 AM, Paul Koning <paulkon...@comcast.net> wrote:
> > On Jun 27, 2018, at 12:36 PM, Eric Smith via cctalk < > cctalk@classiccmp.org> wrote: > > Collision detection was the reason (or at least _a_ reason) why the > spacing > > of taps on the 10BASE-5 "thick" Ethernet cable was required to be an > exact > > multiple of 2.5m. It was never clear to me why this was not also a > > requirement for 10BASE-2 "thin" Ethernet. > > Yes, to avoid false alarms. The purpose of the spacing rule is to ensure > that there is enough signal integrity that you do not get spurious > collision indications due to reflections off the impedance variations along > the cable. On a segment with few transceivers, there is enough margin that > the rule doesn't matter. This is why 10Base-2 doesn't have that rule: the > station count limit is low enough that it isn't needed. > Interesting! I won't disagree with what you're saying, since I'm ignorant of these details, but in my experience 10BASE-2 networks usually had far _more_ nodes on a network than any 10BASE-5 network I saw. I routinely saw over 100 nodes on a 10BASE-2, but I never saw more than 20 or so on a 10BASE-5. (There certainly may have been larger 10BASE-5 networks; I only ever saw about a dozen 10BASE-5 networks.)