IEEE 802.3 Quick Primer
7
Propagation
Round-trip propagation delay throughout the entire cable system, from farthest
ends, may not exceed 51.7
µ
s.
Propagation delay is the time it takes a signal to travel from the input of a system
component to the output. Propagation delay is usually measured in nanoseconds.
IEEE 802.3 has specific propagation delay maximums for the Ethernet
components. Cable length plays a major role in propagation delay. (That is, a 50
meter [164 ft.] AUI cable has a maximum propagation delay of 257 ns.) The
propagation delay of a cable is dependent on the length and velocity factor of the
cable type.
Four Repeater Rule
No more than four repeaters can be linked to connect five segments and no other
attachments may be on the linking segments. If attachments are present on the
repeater coax link segments, then no more than two repeaters linking three
segments may be configured. These limitations are set to keep propagation delay,
packet jitter and signal attenuation to within acceptable standards.
MR125DBook Page 7 Wednesday, August 21, 1996 4:24 PM
