Result: standard mapping
How many E3s are in a STM-256?
A STM-256 carries 768 E3s, per ITU-T G.707.
768
E3s in a STM-256
Working
STM-256 → 256 × STM-1 → 3 × E3
- 256 × STM-1 in each STM-256 ITU-T G.707256 × STM-1.
- 3 × E3 in each STM-1 ITU-T G.707Three VC-3s, each carrying an E3.
- 256 STM-1s
- 256 × 3 = 768 E3s
Leftover capacity
13.418496 Gbit/s of each STM-256 line rate (39.813120 Gbit/s) sits outside 768 × 34.368 Mbit/s of E3 line rate (26.394624 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 1,158.43, which floors to 1,158 E3s by bit rate only. The standard mapping is 768. Use the mapping.