What an OC-1 contains
An OC-1 carries 672 DS0s, per Telcordia GR-253 and ANSI T1.107.
OC-1 (STS-1) → 28 × DS1 → 24 × DS0
- 28 DS1s
- 28 × 24 = 672 DS0s
E1 mapping: 21 E1s, which is 630 voice channels at 30 per E1. E1s in an OC-1.
Down to DS0
- 28 × DS1 Telcordia GR-253Seven VT groups × four VT1.5 (DS1).
- 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 × DS3 Telcordia GR-253Asynchronous DS3 mapping into the STS-1 synchronous payload envelope.
- 7 × DS2 Telcordia GR-253Seven VT groups, one VT6 (DS2) each.
- 21 × E1 Telcordia GR-253Seven VT groups × three VT2 (E1).