Result: standard mapping
How many E3s are in an OTU4?
An OTU4 carries 1,920 E3s, per ITU-T G.709 and ITU-T G.707. This path maps STM-64 into ODU2 as a client, then follows that client's tributaries.
1,920
E3s in an OTU4
Working
OTU4 → 1 × ODU4 → 10 × ODU2 → 1 × STM-64 → 64 × STM-1 → 3 × E3
- 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 × STM-64 in each ODU2 ITU-T G.709Client mappingCBR STM-64 mapped into OPU2.
- 64 × STM-1 in each STM-64 ITU-T G.70764 × STM-1.
- 3 × E3 in each STM-1 ITU-T G.707Three VC-3s, each carrying an E3.
- 1 ODU4
- 1 × 10 = 10 ODU2s
- 1 × 10 × 1 = 10 STM-64s
- 1 × 10 × 1 × 64 = 640 STM-1s
- 1 × 10 × 1 × 64 × 3 = 1,920 E3s
Leftover capacity
45.823413568 Gbit/s of each OTU4 line rate (111.809973568 Gbit/s) sits outside 1,920 × 34.368 Mbit/s of E3 line rate (65.986560 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 3,253.31, which floors to 3,253 E3s by bit rate only. The standard mapping is 1,920. Use the mapping.