Result: standard mapping
How many DS1s are in a STM-4?
A STM-4 carries 336 DS1s, per ITU-T G.707.
336
DS1s in a STM-4
Working
STM-4 → 4 × STM-1 → 84 × DS1
- 4 × STM-1 in each STM-4 ITU-T G.7074 × STM-1.
- 84 × DS1 in each STM-1 ITU-T G.70784 VC-11 tributaries: 3 TUG-3 × 7 TUG-2 × 4 TU-11.
- 4 STM-1s
- 4 × 84 = 336 DS1s
Leftover capacity
103.296 Mbit/s of each STM-4 line rate (622.080 Mbit/s) sits outside 336 × 1.544 Mbit/s of DS1 line rate (518.784 Mbit/s). That remainder is overhead, fixed stuff or justification. It is not another whole tributary.
By bit rate only
Dividing the line rates gives 402.9, which floors to 402 DS1s by bit rate only. The standard mapping is 336. Use the mapping.