This section describes the background and methods of dividing a DCN network into subnets.
The number of NEs in a network increases as the network scale expands, leading to more ECC routes between NEs. Due to the limitations of the communication protocol, the total number of NEs in a DCN network must not exceed the upper limit even though there are sufficient GNEs. If the total number of NEs in the DCN network exceeds the upper limit, some problems are likely to occur. For example, specific NEs are unreachable by the NMS, alarms on the NEs are lost, and the SCC boards on these NEs are reset unexpectedly. To prevent these problems, the DCN network must be divided into subnets and the number of NEs in each DCN subnet complies with the product specifications and ECC communication is not allowed between subnets. For detailed information about subnet scale, see Networking Capability.
NOTICE: After a DCN network is divided into DCN subnets, NEs in different DCN subnets cannot communicate with each other. Therefore, the features or functions that require DCN communication between NEs in different subnets will be unavailable. These features or functions include ALC, APE, EAPE, wavelength locking, and software package loading. It is recommended that you include NEs with these features enabled into one subnet. For a network that uses the HWECC protocol, inter-NE communication between subnets must be planned if NEs in different subnets use these features.
Subnet Division Principles
- The number of NEs in each DCN subnet is within the recommended range.
- The DCC or GCC communication between DCN subnets must be disabled.
- Before dividing a DCN network into subnets, an external DCN must be planned for connecting to GNEs in each subnet.
- The division of a DCN network must not compromise the existing DCN route restoration (protection) capability.
- Electrical and optical NEs belonging to the same site must be in the same DCN subnet.
Subnet Division Methods
Two methods are available for dividing a DCN network into subnets: horizontal division and vertical division.
Horizontal Division
In the case of horizontal division, a DCN network is divided into different DCN subnets based on the service domain that an NE belongs to.
Vertical Division
In the case of vertical division, a DCN network is divided into different DCN subnets by the physical location or topology of the network. This method does not concern whether the NEs on the same DCN subnet belong to the same service domain.
The vertical division also has the following problems:
Operations Related to Subnet Division
- Disable or delete DCN ports on edge NEs in each subnet. Specifically, this operation disables or deletes the edge port DCC or GCC channels of OSC or ESC boards on the edge NEs. NOTICE:
When the ASON protocol is enabled for the network, the DCN channels must be deleted, not just disabled.
- Configure transparent transmission of DCC information on edge NEs in each subnet. Specifically, this operation configures OSC boards or ESC boards on edge NEs to transparently transmit DCC or GCC bytes.