4A0-220 Exam Dumps - Nokia GMPLS-Controlled Optical Networks

The SNC state is a parameter that indicates the status of a resource in a GMPLS network. A resource can be a link, a wavelength, a timeslot, or a fiber. The SNC state can have different values, such as N, n, P, p, R, r, and so on. Each value has a specific meaning and implication for the resource and the LSP that uses it. The SNC state of lower case “n” means that the resource is the nominal resource on a TE-link that is notin use. A nominal resource is the default or preferred resource that is assigned to an LSP when it is created. A TE-link is a logical link that represents a set of resources that share the same attributes and constraints. A TE-link can have multiple resources, such as wavelengths or timeslots, but only one of them can be the nominal resource. If an LSP is using a resource other than the nominal resource on a TE-link, it means that the LSP has been rerouted or switched due to a failure or a constraint violation. In this case, the SNC state of the nominal resource will be “n”, indicating that it is not in use by any LSP12. References:

• 1: Nokia GMPLS-controlled Optical Networks Course | Nokia
• 2: Nokia Network Functions Manager for Transport User Guide | Nokia

Constrained Shortest Path First (CSPF) is an extension of the shortest path first (SPF) algorithm that is used to find the best path for a Label Switched Path (LSP) in a GMPLS network. CSPF takes into account additional constraints such as bandwidth, latency, priority, or node or link inclusion or exclusion. CSPF works by pruning those links that do not meet the specified constraints and then applying the SPF algorithm to the remaining links. This way, CSPF can find a path that satisfies both the shortest distance and the constraints. References : Constrained Shortest Path First - Wikipedia, Constrained Shortest Path First (CSPF) - Metaswitch

The Commissioning File in GMRE nodes is a file with target values that determine whether a given LSP is possible. The Commissioning File contains parameters such as power, OSNR, Q-factor, and dispersion that are used to evaluate the feasibility of an LSP request. The Commissioning File is generated by the Network Planning Application (NPA) based on the network design and optical impairments. The Commissioning File is uploaded to each GMRE node and is used by the CSPF algorithm to find a suitable path for the LSP. References : Nokia GMPLS-controlled Optical Networks Course | Nokia, Network Planning Application (NPA) | Nokia

The Shutting Down state is a transient state that occurs when a TE-link is set to maintenance mode in the NFM-T. In this state, the TE-link is not available for routing new LSPs, but the existing LSPs (SNCs) that use the TE-link are not immediately terminated. Instead, they are soft-rerouted, which means that they are gracefully switched to alternative paths without disrupting the traffic. The Shutting Down state lasts until all the SNCs on the TE-link are successfully soft-rerouted or forcefully terminated. After that, the TE-link transitions to the Administrative Maintenance state, where no traffic can be routed over the TE-link12. References:

• 1: Nokia GMPLS-controlled Optical Networks Course | Nokia
• 2: Nokia Network Functions Manager for Transport User Guide | Nokia