Result: standard mapping
How many DS2s are in an OTU4?
An OTU4 carries 13,440 DS2s, per ITU-T G.709 and Telcordia GR-253. This path maps OC-192 into ODU2 as a client, then follows that client's tributaries.
13,440
DS2s in an OTU4
Working
OTU4 → 1 × ODU4 → 10 × ODU2 → 1 × OC-192 → 192 × OC-1 (STS-1) → 7 × DS2
- 1 × ODU4 in each OTU4 ITU-T G.709The OTU4 frame carries exactly one ODU4.
- 10 × ODU2 in each ODU4 ITU-T G.709Ten ODU2s use all 80 tributary slots, eight slots each.
- 1 × OC-192 in each ODU2 ITU-T G.709Client mappingCBR OC-192, the same client rate as STM-64, mapped into OPU2.
- 192 × OC-1 (STS-1) in each OC-192 Telcordia GR-253192 × OC-1 (STS-1). Channelized OC-192 is 192 STS-1s.
- 7 × DS2 in each OC-1 (STS-1) Telcordia GR-253Seven VT groups, one VT6 (DS2) each.
- 1 ODU4
- 1 × 10 = 10 ODU2s
- 1 × 10 × 1 = 10 OC-192s
- 1 × 10 × 1 × 192 = 1,920 OC-1s
- 1 × 10 × 1 × 192 × 7 = 13,440 DS2s
Leftover capacity
26.976693568 Gbit/s of each OTU4 line rate (111.809973568 Gbit/s) sits outside 13,440 × 6.312 Mbit/s of DS2 line rate (84.833280 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 17,713.87, which floors to 17,713 DS2s by bit rate only. The standard mapping is 13,440. Use the mapping.