Result: standard mapping
How many DS2s are in a STM-256?
A STM-256 carries 5,376 DS2s, per ITU-T G.707 and ANSI T1.107.
5,376
DS2s in a STM-256
Working
STM-256 → 256 × STM-1 → 3 × DS3 → 7 × DS2
- 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.
- 7 × DS2 in each DS3 ANSI T1.107M13 multiplex: seven DS2s.
- 256 STM-1s
- 256 × 3 = 768 DS3s
- 256 × 3 × 7 = 5,376 DS2s
Leftover capacity
5.879808 Gbit/s of each STM-256 line rate (39.813120 Gbit/s) sits outside 5,376 × 6.312 Mbit/s of DS2 line rate (33.933312 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 6,307.52, which floors to 6,307 DS2s by bit rate only. The standard mapping is 5,376. Use the mapping.