Constitution of the DCN

On a DCN, the NMS and all the NEs are nodes of the DCN. The DCN between the NMS and NEs is called an external DCN, and the DCN between NEs is called an internal DCN.

Figure 1 Constitution of the DCN

External DCN

On an actual network, the NMS and NEs may be located on different floors of a building, in different buildings, or even in different cities. Therefore, an external DCN that is comprised of data communication equipment, such as LAN switches and routers, is required to connect the NMS and the NEs.

External DCNs involve data communication. Therefore, no detailed description is provided in this document. Unless otherwise specified, DCNs mentioned in this document refer to internal DCNs.

Internal DCN

The OptiX RTN 905, OptiX RTN 910, OptiX RTN 950, OptiX RTN 950A, OptiX RTN 980 and OptiX RTN 980L supports the port types and transmission channels listed in Table 1 for transmitting network management messages on an internal DCN.

**Table 1** Port types and transmission channels for transmitting network management messages on an internal DCN
Port Type		Transmission Channel
Microwave port	PDH radio	One Huawei-defined DCC byte in a microwave frame (capacity: less than 16xE1) Three Huawei-defined DCC bytes in a microwave frame (capacity: equal to or greater than 16xE1)
	SDH radio	D1 to D3, D4 to D12, or D1 to D12 bytes in a microwave frame NOTE: Only the DCC bytes in the first one of 2xSTM-1 microwave frames are used to transmit network management messages.
	Integrated IP radio NOTE: The OptiX RTN 905 and OptiX RTN 950A do not support.	Three Huawei-defined DCC bytes in a microwave frame Partial Ethernet service bandwidth in a microwave frame
SDH port		D1 to D3, D4 to D12, or D1 to D12 bytes in an SDH frame
NMS port or NE cascade port		All the port bandwidth
External clock port		Some timeslots (serving as DCC bytes) in received E1s
FE/GE port		Ethernet service bandwidth
Multi-functional cascade port NOTE: Only the OptiX RTN 905 supports.		3 bytes (D1 to D3) Partial bandwidth of ML-PPP links over Multi-functional cascade port
Channelized STM-1 port NOTE: The OptiX RTN 905 does not support.		D1 to D3, D4 to D12, or D1 to D12 bytes in an SDH frame Partial bandwidth on a Multi-Link Point-to-Point Protocol (ML-PPP) link
Smart E1 port NOTE: The OptiX RTN 905 does not support.		Partial bandwidth on an ML-PPP link

In an internal DCN, OptiX RTN 605, OptiX RTN 610 and OptiX RTN 620 use the DCC bytes of the overhead as the physical channels of the DCN.

When the D1 byte of the PDH microwave overhead is used, a bandwidth of 64 kbit/s can be provided for the DCN.
When D1-D3 bytes of the PDH microwave overhead are used, a bandwidth of 192 kbit/s can be provided for the DCN.
When D1-D3 bytes of the SDH regenerator section overhead (RSOH) are used, a bandwidth of 192 kbit/s can be provided for the DCN.
When D4-D12 bytes of the SDH multiplex section overhead (MSOH) are used, a bandwidth of 576 kbit/s can be provided for the DCN.
When D1-D12 bytes of the SDH section overhead are used, a bandwidth of 768 kbit/s can be provided for the DCN.
When D1-D3 bytes of the Hybrid microwave overhead are used, a bandwidth of 192 kbit/s can be provided for the DCN.

NOTE:

In the PDH microwave frame or Hybrid microwave frame, the DCC bytes are defined by Huawei.
In the SDH microwave frame, the defined DCC bytes comply with the SDH overhead specifications.

Table 2lists OptiX RTN 310, OptiX RTN 360, OptiX RTN 380 ports and channels that can transmit network management messages on an internal DCN.

**Table 2** Port types and transmission channels for transmitting network management messages on an internal DCN
Port Type	Transmission Channel
Microwave port	Three Huawei-defined data communications channel (DCC) bytes in a microwave frame Ethernet service bandwidth in a microwave frame
NMS port or NE cascade port	All bandwidths at the NMS port
GE port	Ethernet service bandwidth
1+1 cascade port	Ethernet bandwidth

Gateway NE and Non-Gateway NE

Generally, a gateway NE is connected to an NMS through a LAN/WAN. The application layer of the NMS directly communicates with the application layer of the gateway NE. One NMS needs to be connected to one or more gateway NEs.

A non-gateway NE communicates with its gateway NE through DCN channels between them.

Inband DCN and Outband DCN

Inband DCN is a DCN networking mode that uses a portion of service bandwidth for data communication. For example, the OptiX RTN 980uses Integrated IP radio ports or the Ethernet service bandwidth on FE/GE ports to transmit network management messages.
Outband DCN is a DCN networking mode that does not use service bandwidth for data communication. For example, the OptiX RTN 980uses DCC bytes (in microwave frames or SDH frames, or on or external clock ports), an NMS port, or an NE cascade port to transmit network management messages.