Rerouting policy when ASON network resources are insufficient


Rerouting policy when ASON network resources are insufficient:
When the resource of a link is insufficient, the VC4 service will be rerouted to a different link until there is no idle resources.

Other related questions:
Rerouting rules of Huawei WDM/OTN ASON systems
Through traffic engineering, a WDM/OTN ASON network has various rerouting constrains: 1. Constraints on explicit network resources: explicit nodes, links, wavelengths, and channels 2. Constraints on excluded network resources: excluded nodes and links 3. Limitation on the quantity of nodes (or hops) traversed by a strict route or service 4. Limitation on the reach of an optical fiber carrying services, loading sharing mode, SRLGs, and associated services 5. Combinations of the preceding constraints

Parameters that are considered and computed for ASON rerouting
To achieve dynamic rerouting for optical-layer ASON services and ensure service transmission quality, optical parameters must be considered, such as OSNR, CD, and PMD. In addition, they need to be included in service routing constraints.

Rerouting policies of diamond services
The rerouting policies for diamond services are described as follows: Permanent 1+1 protection: Rerouting is triggered when either the working or protection LSP is interrupted. Rerouting 1+1 protection: Rerouting is triggered only when both the working and protection LSPs are interrupted. Flex P&R: In this rerouting policy, P indicates the number of protection times. R indicates the number of rerouting times. Before P is used up, rerouting is triggered when either the working or protection trail becomes faulty. After P is used up, rerouting is triggered only when both the working and protection LSPs become faulty. After R is used up, rerouting is stopped. Non-rerouting 1+1 protection. No rerouting is triggered upon interruption of LSPs regardless of the working or protection LSP. On the NMS, the configuration of electrical-layer ASON services depends on the rerouting policies. On the page for creating electrical-layer diamond services, the services can be configured by setting the Trigger Condition parameter in Routing Attributes . There are four types of trigger conditions: 1. Rerouting is triggered when any LSP is interrupted. 2. Rerouting is triggered when both LSPs are interrupted. 3. Rerouting is not triggered. 4. Rerouting is triggered based on the flex P&R protection policy.

Precautions for setting rerouting trigger conditions on an ASON network
Rerouting trigger conditions are determined based on the number of available network resources and service importance. If there are sufficient resources or protected services are important, you can select the policy of triggering rerouting when any LSP fails. In this way, 1+1 protection is retained for services under SNCP protection or optical-layer associated services, and quick switching can be achieved upon a fault. Even if a rerouting failure occurs, the failure can be detected in a timely manner. If there are insufficient resources or the protected services are less important, you can select the policy of rerouting when both LSPs fail. In this way, the 1+1 protection provided for the services can survive only one fault. When both LSPs fail and service rerouting is triggered, the service will be interrupted for a short time (depending on the rerouting time), or be interrupted for a long time if rerouting fails.

Method used to select routing policies on an ASON network
Various rerouting policies are provided on an ASON network and are selected based on the available system resources. When the resources are sufficient, diamond services can be used. As resources are continuously consumed, a user may have to select copper services to ensure that sufficient resources are provided for diamond services. Copper services are rarely used. Generally, only temporary services are configured as copper services.

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