Last Updated: August 16, 2025
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A Lower Order-ODU or LO-ODU is an ODUk, whose OPUk transports a inside mapped client.

An Higher Order-ODU or HO-ODU is an ODUk, whose OPUk transports an inside multiplexed ODUj.
LO-ODU and HO-ODU have the same structure but with different clients.
The LO-ODU is either mapped into the associated OTUk or multiplexed into an HO-ODU.
The HO-ODU is mapped into the associated OTUk.
Please notice that, HO-ODUj multiplexed into HO-ODUk is an undesired hierarchy in one domain.
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