Result: standard mapping
How many E4s are in an OTU4?
An OTU4 carries 640 E4s, per ITU-T G.709 and ITU-T G.707. This path maps STM-64 into ODU2; E4 into STM-1 as a client, then follows that client's tributaries.
640
E4s in an OTU4
Working
OTU4 → 1 × ODU4 → 10 × ODU2 → 1 × STM-64 → 64 × STM-1 → 1 × E4
- 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.
- 1 × E4 in each STM-1 ITU-T G.707Client mappingAsynchronous E4 mapped into the C-4 / VC-4. This client holds 64 E1s internally; the VC-12 tributary count of an STM-1 is 63.
- 1 ODU4
- 1 × 10 = 10 ODU2s
- 1 × 10 × 1 = 10 STM-64s
- 1 × 10 × 1 × 64 = 640 STM-1s
- 1 × 10 × 1 × 64 × 1 = 640 E4s
Leftover capacity
22.681013568 Gbit/s of each OTU4 line rate (111.809973568 Gbit/s) sits outside 640 × 139.264 Mbit/s of E4 line rate (89.128960 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 802.86, which floors to 802 E4s by bit rate only. The standard mapping is 640. Use the mapping.