Most types of OTU boards in the NGWDM equipment support the ESC mode; however, the SC2 board is generally configured in the existing networks so that the NGWDM equipment also supports the OSC mode. That is, the NGWDM equipment provides the ESC and OSC modes for options.
If both the OSC and ESC modes exist between two NEs, the priority arrangement of the DCCs in practice are as follows:
1. GCC12_18 > GCC12_9|D4�D12 > D1�D3|GCC0 > Pilot tone modulated DCC
2. Under the same available DCC bandwidth, a time sequence is followed for the priority arrangement of the DCCs.
The time sequence refers to an order in which the NE software identifies the DCCs one by one rather than the sorting of the DCC numbers from small to big. The time sequence of boards depends on the time points when the boards get online. The NE software preferably selects the DCC of the board that gets online early to transmit supervisory information.
Note: Some OTU boards of the NGWDM equipment also support channel D1�D3 if the WDM-side service type of the board is set to SDH, such as the L4G board.
The preceding description shows that the priority of the ESC mode is higher than the OSC mode on the NGWDM equipment. When both the OSC and ESC modes exist, the ESC is preferred for transmit of supervisory information.