What a STM-256 contains
A STM-256 carries 516,096 DS0s, per ITU-T G.707 and ANSI T1.107.
STM-256 → 256 × STM-1 → 84 × DS1 → 24 × DS0
- 256 STM-1s
- 256 × 84 = 21,504 DS1s
- 256 × 84 × 24 = 516,096 DS0s
E1 mapping: 16,128 E1s, which is 483,840 voice channels at 30 per E1. E1s in a STM-256.
Down to DS0
- 256 × STM-1 ITU-T G.707256 × STM-1.
- 84 × DS1 ITU-T G.70784 VC-11 tributaries: 3 TUG-3 × 7 TUG-2 × 4 TU-11.
- 24 × DS0 ANSI T1.10724 payload timeslots. The framing bit adds 8 kbit/s and brings the line rate to 1.544 Mbit/s.
- 1 × E4 ITU-T G.707Client mappingAsynchronous E4 mapped into the C-4 / VC-4. This client holds 64 E1s internally; the VC-12 tributary count of an STM-1 is 63.
- 3 × E3 ITU-T G.707Three VC-3s, each carrying an E3.
- 3 × DS3 ITU-T G.707Three VC-3s, each able to carry a DS3.
- 63 × E1 ITU-T G.70763 VC-12 tributaries: 3 TUG-3 × 7 TUG-2 × 3 TU-12.
- 84 × DS1 ITU-T G.70784 VC-11 tributaries: 3 TUG-3 × 7 TUG-2 × 4 TU-11.
- 4 × STM-64 ITU-T G.7074 × STM-64.
- 16 × STM-16 ITU-T G.70716 × STM-16.
- 64 × STM-4 ITU-T G.70764 × STM-4.