Silver WDM ASON Trail

Silver WDM ASON trail, including WDM ASON OCh trails, ODU0 trails, ODU1 trails, ODU2 trails, ODU3 trail and ODU4 trails, the revertive time is several seconds. The silver level service is suitable for those data or internet services that have low real-time requirement.

Silver services are also called rerouting services. When an LSP failure, the ASON triggers rerouting to restore the service. If there are not enough resources, service may be interrupted.

As shown in Figure 1, A-B-G-H-I is a silver service trail. If the fiber between B and G is cut, the ASON triggers rerouting from A to create an LSP that does not pass the cut fiber. Hence, services are protected.

Figure 1 A silver service

Table 1 lists the attributes of silver services.

**Table 1** Attributes of silver services
Attribute	Silver Services
Requirements for creation	Sufficient non-protection resources are available between the source node and the sink node.
Service restoration	When the original LSP fails, rerouting is triggered to create an LSP to restore services.
Rerouting	Supports setting the revertive mode. Supports setting the WTR time. Supports setting the scheduled reversion time. Supports setting revertive lockout. Supports rerouting lockout. Supports setting the rerouting priority. Supports setting the crankback times. Supports setting the trigger condition. Supports five rerouting policies: Use existing trails whenever possible Do not use existing trails whenever possible No rerouting constraint Use simulated section restoration Use preset restoration Supports rerouting triggered by SD. Supports setting the rerouting hold-off time.
Revertive	Supports Automatically Revertive, Non-Revertive, and Scheduled revertive. After the automatically revertive diamond service is rerouted, the service is automatically reverted to the original path if the fault in the original path is rectified. After the scheduled revertive diamond service is rerouted, the user can set the service to be reverted to the original path at a specific future time (ranging from 10 minutes to 30 days) on the NMS if the fault in the original path is rectified. After the non-revertive diamond service is rerouted, the service is not reverted to the original route after the fault is rectified.
Preset restoration trail	Supports setting two preset restoring trails. Preset restoration trails are preferred in rerouting.
Service upgrade and downgrade	Supports traditional unprotected WDM trails upgrade to silver WDM ASON trails. Supports silver WDM ASON trails downgrade to traditional unprotected WDM trails.
Service migration	Migration between optical-layer WDM ASON OCh trails is not supported. Supports migration between electrical-layer silver WDM ASON trails and diamond WDM ASON trails. Supports migration between electrical-layer silver WDM ASON trails and copper WDM ASON trails.
Service optimization	Supports manual service optimization.
Service association	Supports service association.