Result: standard mapping
How many E4s are in an ODU2?
An ODU2 carries 64 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.
64
E4s in an ODU2
Working
ODU2 → 1 × STM-64 → 64 × STM-1 → 1 × E4
- 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 STM-64
- 1 × 64 = 64 STM-1s
- 1 × 64 × 1 = 64 E4s
Leftover capacity
1.124377924 Gbit/s of each ODU2 line rate (10.037273924 Gbit/s) sits outside 64 × 139.264 Mbit/s of E4 line rate (8.912896 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 72.07, which floors to 72 E4s by bit rate only. The standard mapping is 64. Use the mapping.