4A0-220 Nokia GMPLS-Controlled Optical Networks Questions and Answers

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

Tunnel Property Heritage is a feature of GMRE that allows the propagation of certain properties from higher order (HO) LSPs to lower order (LO) LSPs in a multi-layer network. These properties include cost, SRLG, and color. Cost is a metric that reflects the preference of using a certain link or path for routing. SRLG is a set of links that share a common risk of failure. Color is an attribute that can be used to group or filter LSPs based on service classes or customer profiles. By propagating these properties from HO to LO LSPs, GMRE can ensure that the end-to-end LSPs are consistent and optimal across different layers34. References:

• 3: Nokia GMPLS-controlled Optical Networks Course | Nokia
• 4: GMPLS - Nokia

A Label Switched Path (LSP) is the path created by MPLS nodes that use labels to forward packets across the network. A label is a short identifier that is attached to each packet and indicates the next hop or destination of the packet. The nodes use a label forwarding table to switch packets based on their labels, without inspecting the packet headers. This can improve the performance, security, and quality of service of the network. An LSP can be established by using GMPLS protocols such as OSPF-TE and RSVP-TE, which exchange information about the network topology, resources, and constraints. References : Nokia GMPLS-controlled Optical Networks Course | Nokia, GMPLS - Nokia

The Soft Shutting Down state in the NFM-T is an administrative maintenance state where services stay up but no new traffic can be routed over the TE-link. This state is used to prepare a TE-link for maintenance or decommissioning without affecting the existing services. The NFM-T sets the TE-link to Soft Shutting Down state by sending a Notify message with the Administrative State Change flag to the head-end node of the TE-link. The head-end node then stops accepting new LSP requests over the TE-link and sends a PathErr message with the Administrative State Change flag to all the tail-end nodes of the LSPs in the TE-link. The tail-end nodes then stop sending new traffic over the LSPs and send a ResvErr message with the Administrative State Change flag to all the intermediate nodes of the LSPs. The intermediate nodes then update their routing tables and stop forwarding new traffic over the LSPs. The existing traffic, however, continues to flow over the LSPs until they are manually deleted or rerouted by the NFM-T. References : Nokia GMPLS-controlled Optical Networks Course | Nokia, Nokia Advanced Optical Network Management with NFM-T Course | Nokia

The label on the top of the MPLS label stack is swapped at an intermediate node. This is because the top label is the one that is visible to the node and determines the forwarding decision. The node looks up the top label in its label forwarding table and swaps it with a new label that corresponds to the next hop or destination. The node then forwards the packet to the next node, which repeats the same process. The bottom label is only used to indicate the end of the label stack and is not swapped. References : [Nokia GMPLS-controlled Optical Networks Course | Nokia], [MPLS Label Stack - Nokia]

The Link Maintenance window is a feature of NFM-T that allows the user to perform maintenance tasks on links and nodes in a GMPLS network. The Link Maintenance window is a wizard that provides commands to set links and nodes to maintenance mode, which prevents them from being used for routing new LSPs or carrying traffic. The user can also use the Link Maintenance window to reroute existing LSPs away from the links and nodes that are in maintenance mode, either manually or automatically. The Link Maintenance window helps the user to perform network maintenance operations without disrupting the service availability or quality12. References:

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

GMPLS stands for Generalized Multi-Protocol Label Switching, which is a protocol suite that extends MPLS to control different types of switching technologies, such as optical, TDM, and packet switching1. The meaning of Generalized in GMPLS is that it can be used for traffic types other than data packets, such as wavelengths, time slots, or fibers2. GMPLS can also use implicit labels that are derived from the physical properties of the data stream, such as wavelength or timeslot, instead of explicit labels that are carried in the packet header3. This allows GMPLS to support various transport networks and applications, such as optical transport networks (OTN), wavelength switched optical networks (WSON), and automatic switched optical networks (ASON)4. References:

• 1: Nokia GMPLS-controlled Optical Networks Course | Nokia
• 2: What is MPLS and GMPLS? - Metaswitch
• 3: Generalized Multi-Protocol Label Switching - Wikipedia
• 4: GMPLS - Nokia

The OSPF-TE protocol is an extension of the Open Shortest Path First (OSPF) protocol that is used to exchange information about the state of links in a GMPLS network. OSPF-TE advertises link attributes such as bandwidth, latency, priority, protection, or switching capabilities to other nodes in the same area. OSPF-TE enables nodes to build a Traffic Engineering Database (TED) that contains the topology and resource information of the network. OSPF-TE helps nodes to perform CSPF calculations and establish LSPs using RSVP-TE signaling. References : Open Shortest Path First - Wikipedia, Understand Open Shortest Path First (OSPF) - Design Guide, RSVP-TE and OSPF-TE extensions for GMPLS

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