To clarify an OC3:
'OC' does stand for optical carrier. The '3' means that it is equal to 3 DS3s. So an OC3 is equal to 3 x DS3 (45mb), or 3x45mb=135mb. A DS3 is equal to 28 T1s (1.544mb), or 672 56k (DS0) circuits. Another way to think about it: say the average dialup is 28.8kbps, a DS3 equals 1444 dialup connections and an OC3 is 3 times that (4332).
