Result: standard mapping
How many DS2s are in an OC-3?
An OC-3 carries 21 DS2s, per Telcordia GR-253.
21
DS2s in an OC-3
Working
OC-3 → 3 × OC-1 (STS-1) → 7 × DS2
- 3 × OC-1 (STS-1) in each OC-3 Telcordia GR-2533 × OC-1 (STS-1). Channelized OC-3 is 3 STS-1s.
- 7 × DS2 in each OC-1 (STS-1) Telcordia GR-253Seven VT groups, one VT6 (DS2) each.
- 3 OC-1s
- 3 × 7 = 21 DS2s
Leftover capacity
22.968 Mbit/s of each OC-3 line rate (155.520 Mbit/s) sits outside 21 × 6.312 Mbit/s of DS2 line rate (132.552 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 24.63, which floors to 24 DS2s by bit rate only. The standard mapping is 21. Use the mapping.