4A0-220 Sample Questions Answers

Signaling protocols are protocols that are used by the ingress router to set up a new LSP in an MPLS network. Signaling protocols are responsible for requesting, allocating, and releasing resources along the LSP, as well as establishing and maintaining the label bindings between the nodes. Some examples of signaling protocols are RSVP-TE, LDP, and CR-LDP34. References:

• 3: Nokia GMPLS-controlled Optical Networks Course | Nokia
• 4: MPLS Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 7.1.x - Implementing MPLS Label Distribution Protocol [Cisco IOS XR Software (End-of-Sale)] - Cisco

A distributed control plane for GMPLS means that each router has software to run the GMPLS protocols and can modify the node’s switching fabric. This allows the routers to communicate with each other and establish Label Switched Paths (LSPs) across the network without relying on a centralized controller or network manager. A distributed control plane can improve the scalability, reliability, and efficiency of the network. References : Nokia GMPLS-controlled Optical Networks Course | Nokia, GMPLS - Nokia

To configure the Trail template in NFM-T for an Uplink board (such as 2UC400) in a network with only LI restoration capability, you need to check the Logical Link box, set the Port Type to Unterminated, uncheck the ASON Routed box, and uncheck the ASON Tunnel box. This configuration allows you to create a logical link between two Uplink boards that can be used for LI restoration. The logical link is not terminated at the Uplink board, but at the OTU board. The ASON Routed option is not needed for LI restoration, as the LSPs are established by NFM-T and not by GMPLS. The ASON Tunnel option is not applicable for Uplink boards. References : Nokia Advanced Optical Network Management with NFM-T Course | Nokia, Nokia 1830 PSS-4, PSS-8, PSS-16 and PSS-32 Platforms - NATO

The GMRE functionality is guaranteed in Nokia equipment by controller redundancy. The controller is the hardware component that runs the GMPLS software and controls the switching fabric of the node. Each node has two controllers, one active and one standby, that synchronize their states and databases. If the active controller fails, the standby controller takes over and ensures the continuity of the GMRE functionality. References : Nokia GMPLS-controlled Optical Networks Course | Nokia, 1830 Photonic Service Switch (PSS) | Nokia

RSVP-TE Notify message is a message type defined in the RSVP-TE protocol, which is an extension of the RSVP protocol for MPLS traffic engineering. RSVP-TE Notify message is used to inform non-adjacent nodes of LSP events, such as setup, modification, or teardown. This allows the nodes to update their local state information and perform actions based on the notification. For example, a Notify message can be used to trigger a fast reroute mechanism in case of a link or node failure12. References:

• 1: RFC 3473 - Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource Reservation Protocol-Traffic Engineering (RSVP-TE) Extensions
• 2: RFC 3471 - Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description

A Nominal Route in a GMPLS network is the optimal path that meets the Traffic Engineering (TE) constraints for a given LSP request. A Nominal Route is calculated by the NFM-T using the Constrained Shortest Path First (CSPF) algorithm, which takes into account parameters such as bandwidth, latency, priority, protection type, and other QoS attributes. A Nominal Route is stored in the NFM-T database and can be used to provision LSPs over the network. A Nominal Route can differ from the Current Route, which is the actual path that the LSP is taking at a given time, due to network changes or failures. References : Nokia GMPLS-controlled Optical Networks Course | Nokia, Nokia Advanced Optical Network Management with NFM-T Course | Nokia

The SNC state with an uppercase “N” means that the resource is currently using the nominal resource assigned to it. As explained in the previous question, a nominal resource is the default or preferred resource that is assigned to an LSP when it is created. If an LSP is using the nominal resource on a TE-link, it means that the LSP has not been rerouted or switched due to any failure or constraint violation. In this case, the SNC state of the resource will be “N”, indicating that it is in use by an LSP12. References:

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

GMPLS is a protocol suite that extends the MPLS signaling and routing capabilities to control different types of switching technologies, such as optical, TDM, and packet switching1. GMPLS has several key features, such as self-discovery, fast protection, and restoration. Self-discovery allows GMPLS nodes to automatically discover their neighbors and exchange information about their capabilities and resources2. Fast protection enables GMPLS nodes to quickly switch to backup paths in case of a failure, without relying on the control plane3. Restoration allows GMPLS nodes to dynamically establish new paths in the network after a failure, using the control plane3. Resource optimization is not a key feature of GMPLS, but rather a potential benefit of using GMPLS to efficiently utilize the network resources and avoid over-provisioning. References:

• 1: Nokia GMPLS-controlled Optical Networks Course | Nokia
• 2: GMPLS - Nokia
• 3: Traffic survivability through Protection and Restoration Combined (PRC) - YouTube
• [4]: GMPLS: Architecture and Applications - Google Books