DCN Communication Channels

Huawei's WDM devices can use either OSC or ESC channels to carry DCN communication protocol packets for DCN communication.

Comparison

Table 1 describes the differences in functions and features of the OSC and the ESC.

**Table 1** Comparison between OSC and ESC
Item	OSC	ESC
Principle	The OSC board provides private optical supervisory channels for the WDM equipment to transmit the supervisory information of the NEs.	The ESC transfers the NE supervisory information by using the overhead bytes (DCCs/GCCs) in the fixed frame structure of the service. In this case, the communication between NEs can be achieved directly through the interconnection of the OTU units, tributary units or line units.
Functions and Features	Occupies private wavelength to transmit the supervisory, OAM information. Ensures that the ultra-long transmission can be achieved without the signal amplification. Uses the CMI line encoding. The sensitivity of the receive side is greater than -48 dBm.	Transfers the supervisory information through the interconnection of the OTU units, tributary units or line units so that dedicated supervisory unit is not required. Transfers the supervisory information along with the primary service signals. Transfers the supervisory information without occupying wavelength resource.
Applicable board	HSC1/SC1/SC2/ST2/DAS1	OTU, tributary board, line board
Transmission channel	D1-D3, D4-D12, OSC_18, FE_DCN	GCC0, GCC0_18, GCC12_9, GCC12_18, GCC1_24, GCCM_24, RES_ODU, pilot tune DCC
Maximum distance	Smaller than 200 km. The value depends on board types.	No limit. The value depends on service type.
Stability	High	Medium
Cost	Because the optical supervisory channel board is used, the cost is relatively high.	Low
Maintainability	High	Low
Stability of ECC topology	Fixed and stable	Low. The stability varies according to services.
Restriction	All NEs, except for the extended ECC subrack, require the optical supervisory channel board	The OLA stations cannot be managed.
The GCC0_18 and GCC1_24 channels are supported only by coherent boards. The D4-D12, GCC1_24, RES_ODU, and GCCM_24 channel bytes are used to transmit ASON information by default. Users can configure them to transmit ASON or DCN information on the NMS.

NOTE:

The ESC-based ECC network topology depends on the allocation of wavelengths, which is more flexible than the OSC. The disadvantage of the ESC-based ECC network topology is that it is inconvenient for management and maintenance.