The provisioning steps that are common in both CP to plain MP networks are node creation, CPB provisioning process, node synchronization, and CPB power balance. These steps are required to create and commission the nodes, provision the cross-connect boards (CPBs), associate the links between the nodes, synchronize the network elements (NEs) with the NFM-T, and balance the power levels of the CPBs. References : Nokia GMPLS-controlled Optical Networks Course | Nokia, Nokia Advanced Optical Network Management with NFM-T Course | Nokia
Questions 5
How are L0 and L1 resources coordinated in case of a failure in an MRN?
Options:
A.
Coordination is achieved by setting the color constraints
B.
Coordination is achieved by comparing the Setup Priorities
C.
Coordination is achieved by segregation of color and colorless LSPs
D.
Coordination is achieved by setting the WSR parameter
Coordination of L0 and L1 resources in case of a failure in an MRN is achieved by setting the color constraints. Color constraints are used to specify which wavelengths or timeslots can be used by a given LSP request. By setting the color constraints, the NFM-T can ensure that the L0 and L1 resources are compatible and consistent across the network. For example, if an L0 LSP request requires a specific wavelength, the NFM-T can set the color constraint to match that wavelength and assign it to the L0 LSP. Similarly, if an L1 LSP request requires a specific timeslot, the NFM-T can set the color constraint to match that timeslot and assign it to the L1 LSP. This way, the coordination of L0 and L1 resources is achieved by ensuring that the same color is used by both layers. References : Nokia GMPLS-controlled Optical Networks Course | Nokia, 3. GMPLS - Nokia
Questions 6
What does the SNC state with an uppercase "N" mean in a resource in NFM-T?
Options:
A.
Indicates it's using a link other than the Nominal
B.
Indicates the nominal resource on a TE-link that is not in use
C.
Indicates if s a higher alarm state level
D.
Indicates it's currently using the Nominal resource assigned to it
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
Questions 7
What is the purpose of the RSVP-TE Notify message?
Options:
A.
It is the node's alarm control channel
B.
It is a mechanism to inform the NM5 of L5P events
C.
It is a mechanism to inform non-adjacent nodes of LSP events
D.
It is confirmation of a node's resource reservation
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:
A Shared Risk Link Group (SRLG) is a set of links sharing a common resource, which affects all links in the set if the common resource fails5. These links share the same risk of failure and are therefore considered to belong to the same SRLG. For example, links sharing a common fiber are said to be in the same SRLG because a fault with the fiber might cause all links in the group to fail. SRLGs are used in MPLS and GMPLS networks to provide traffic engineering and protection/restoration mechanisms. When computing the secondary path for an LSP, it is preferable to find a path such that the secondary and primary paths do not have any links in common in case the SRLGs for the primary and secondary paths are disjoint6. This ensures that a single point of failure on a particular link does not bring down both the primary and secondary paths in the LSP. References:
5: Shared risk resource group - Wikipedia
6: Shared Risk Link Groups for MPLS | Junos OS | Juniper Networks
Questions 9
Which of the following statements about the Wait for Server Restoration (WSR) parameter in the MRN is correct?
Options:
A.
When WSR is true, the LO optical channel remains in the link until the failure is fixed.
B.
When WSR is false, if the failed optical channel can be restored at LO, the data traffic stays in the tunnel.
C.
When WSR is true, the LO channels do not wait for the LI services to restore.
D.
When WSR is false, the LI services do not wait for the LO restoration and restore through LI switching.
The Wait for Server Restoration (WSR) parameter in the MRN is a boolean parameter that determines whether an LI service should wait for the LO restoration or not in case of a failure.When WSR is false, the LI services do not wait for the LO restoration and restore through LI switching. This means that if an LO optical channel fails, the LI services that use that channel will switch to another available optical channel at LI layer without waiting for the LO layer to restore the failed channel. This option provides faster restoration time for LI services, but may result in suboptimal resource utilization at LO layer. When WSR is true, the LI services wait for the LO restoration and do not switch at LI layer. This means that if an LO optical channel fails, the LI services that use that channel will remain in that channel until the LO layer restores it or until a timeout occurs. This option provides optimal resource utilization at LO layer, but may result in longer restoration time for LI services. References : Nokia GMPLS-controlled Optical Networks Course | Nokia, 3. GMPLS - Nokia
Questions 10
What category of protocols is used by the ingress router to set up a new LSP?
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
Questions 11
What is the purpose of preemption when establishing an LSP?
Options:
A.
To measure the end-to-end latency
B.
To pick the next hop during LSP signalling
C.
To tear down an existing LSP in order to accommodate higher priority traffic
D.
To assign the correct wavelengths depending on the type of traffic
Preemption is a mechanism that allows a higher priority LSP to tear down an existing lower priority LSP in order to obtain the required resources for its establishment. Preemption can occur when there is not enough bandwidth or other resources available on a link or node to accommodate a new LSP request. In this case, the node can select one or more lower priority LSPs that are using the resources and send them a PathErr message with a Preempt error code. This causes the lower priority LSPs to beterminated and release their resources. The node can then allocate the resources to the higher priority LSP and send a Resv message to confirm its reservation34. References:
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
Exam Code: 4A0-220
Exam Name: Nokia GMPLS-Controlled Optical Networks
