Result: standard mapping
How many E1s are in an OTU3?
An OTU3 carries 16,128 E1s, 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.
16,128
E1s in an OTU3
Working
OTU3 → 1 × ODU3 → 1 × STM-256 → 256 × STM-1 → 63 × E1
- 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.
- 63 × E1 in each STM-1 ITU-T G.70763 VC-12 tributaries: 3 TUG-3 × 7 TUG-2 × 3 TU-12.
- 1 ODU3
- 1 × 1 = 1 STM-256
- 1 × 1 × 256 = 256 STM-1s
- 1 × 1 × 256 × 63 = 16,128 E1s
Leftover capacity
9.988269559 Gbit/s of each OTU3 line rate (43.018413559 Gbit/s) sits outside 16,128 × 2.048 Mbit/s of E1 line rate (33.030144 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 21,005.08, which floors to 21,005 E1s by bit rate only. The standard mapping is 16,128. Use the mapping.