Result: standard mapping
How many DS3s are in a STM-256?
A STM-256 carries 768 DS3s, per ITU-T G.707.
768
DS3s in a STM-256
Working
STM-256 → 256 × STM-1 → 3 × DS3
- 256 × STM-1 in each STM-256 ITU-T G.707256 × STM-1.
- 3 × DS3 in each STM-1 ITU-T G.707Three VC-3s, each able to carry a DS3.
- 256 STM-1s
- 256 × 3 = 768 DS3s
Leftover capacity
5.455872 Gbit/s of each STM-256 line rate (39.813120 Gbit/s) sits outside 768 × 44.736 Mbit/s of DS3 line rate (34.357248 Gbit/s). That remainder is overhead, fixed stuff or justification. It is not another whole tributary.
By bit rate only
Dividing the line rates gives 889.95, which floors to 889 DS3s by bit rate only. The standard mapping is 768. Use the mapping.