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

A network with ROADM GMPLS nodes and optical transponder connections could have both L0 and L1 restoration capabilities. L0 restoration refers to the ability of the network to recover from failures at the optical layer, such as fiber cuts or node failures, by rerouting the affected LSPs to alternative paths at the same layer. L0 restoration can be achieved by using GMPLS signaling protocols, such as RSVP-TE or CR-LDP, to establish backup LSPs in advance or on demand. L0 restoration can provide fast recovery times and high availability for optical services34. L1 restoration refers to the ability of the network to recover from failures at the sub-wavelength layer, such as transponder failures or wavelength unavailability, by rerouting the affected LSPs to alternative paths at a higher layer. L1 restoration can be achieved by using GMPLS routing protocols, such as OSPF-TE or ISIS-TE, to advertise the sub-wavelength information and availability to other nodes in the network. L1 restoration can provide more flexibility and efficiency for sub-wavelength services56. References:

• 3: GMPLS - Nokia
• 4: Generalized Multi-Protocol Label Switching - Wikipedia
• 5: Sub-Wavelength Switching - Nokia
• 6: Sub-Wavelength Switching in Optical Networks - IEEE Xplore

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]

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