Result: standard mapping
How many DS3s are in an OTU3?
An OTU3 carries 768 DS3s, per ITU-T G.709 and ITU-T G.707. This path maps STM-256 into ODU3 as a client, then follows that client's tributaries.
768
DS3s in an OTU3
Working
OTU3 → 1 × ODU3 → 1 × STM-256 → 256 × STM-1 → 3 × DS3
- 1 × ODU3 in each OTU3 ITU-T G.709The OTU3 frame carries exactly one ODU3.
- 1 × STM-256 in each ODU3 ITU-T G.709Client mappingCBR STM-256 mapped into OPU3.
- 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.
- 1 ODU3
- 1 × 1 = 1 STM-256
- 1 × 1 × 256 = 256 STM-1s
- 1 × 1 × 256 × 3 = 768 DS3s
Leftover capacity
8.661165559 Gbit/s of each OTU3 line rate (43.018413559 Gbit/s) sits outside 768 × 44.736 Mbit/s of DS3 line rate (34.357248 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 961.6, which floors to 961 DS3s by bit rate only. The standard mapping is 768. Use the mapping.