Result: standard mapping
How many E0s are in a STM-256?
A STM-256 carries 483,840 E0s, per ITU-T G.707 and ITU-T G.704.
483,840
E0s in a STM-256
Working
STM-256 → 256 × STM-1 → 63 × E1 → 30 × E0
- 256 × STM-1 in each STM-256 ITU-T G.707256 × STM-1.
- 63 × E1 in each STM-1 ITU-T G.70763 VC-12 tributaries: 3 TUG-3 × 7 TUG-2 × 3 TU-12.
- 30 × E0 in each E1 ITU-T G.70430 voice channels in 32 timeslots. TS0 is framing and TS16 is channel-associated signalling.
- 256 STM-1s
- 256 × 63 = 16,128 E1s
- 256 × 63 × 30 = 483,840 E0s
Leftover capacity
8.847360 Gbit/s of each STM-256 line rate (39.813120 Gbit/s) sits outside 483,840 × 64 kbit/s of E0 line rate (30.965760 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 622,080, which floors to 622,080 E0s by bit rate only. The standard mapping is 483,840. Use the mapping.