Consider a slotted ring of length 20 km with a data rate of

Consider a slotted ring of length 20 km with a data rate of 100 Mbps and 1000 repeaters, each of which introduces a 1-bit delay. Each slot contains room for one source address byte, one destination address byte, two data bytes, and 8 control bits for a total length of 40 bits. How many slots are on the ring?

Solution

The propagation time around the ring:

Tprop = [1000 repeaters / (10^7 sec/repeater)] + [(20000m) / (200 × 106^m/sec)] = 200 × 10^–6 sec

The \"bit length\" of the ring:

Lb = (200 × 10^–6 sec) × (10^7 bits/sec) = 2000 bits

We have [2000 bits / (40 bits/slot)] = 50 slots

There are 50 slots on the ring.