[2024年07月25日]4A0-220問題集完全版問題、試験学習ガイド
Nokia Optical Network Services Expert無料認定試験材料GoShikenからの40問題
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質問 # 19
Which of the following information is present in every GMPLS-enabled node?
- A. The frequency of each client path in the entire network
- B. The bandwidth of each client path in the entire network
- C. The state of each link in the entire network
- D. The list of LSPs created in the entire network
正解：C
解説：
Explanation
GMPLS-enabled nodes use routing protocols, such as OSPF-TE or ISIS-TE, to exchange information about the topology and the state of the links in the network12. This information includes the link attributes, such as bandwidth, wavelength, protection, and shared risk link groups (SRLGs)3. The state of each link indicates whether it is up or down, available or reserved, and so on. This information is used by GMPLS-enabled nodes to compute feasible paths for LSPs and to avoid routing loops or conflicts. The bandwidth and the frequency of each client path are not present in every GMPLS-enabled node, but only in the ingress and egress nodes that initiate and terminate the LSPs. The list of LSPs created in the entire network is also not present in every GMPLS-enabled node, but only in the nodes that are involved in the LSPs or that maintain a global view of the network. References:
* 1: GMPLS - Nokia
* 2: Generalized Multi-Protocol Label Switching - Wikipedia
* 3: Nokia GMPLS-controlled Optical Networks Course | Nokia
質問 # 20
Which label is swapped in an MPLS label stack at an intermediate node?
- A. The label with the highest value
- B. The label on the bottom
- C. The label on the top
- D. The label with the lowest value
正解：C
解説：
Explanation
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]
質問 # 21
When should two physical connections belong to the same SRG?
- A. When they share the same risk of failure
- B. When they are both selected during the setup process
- C. When they are fully disjoint respective to the risk of failure
- D. When one is the protection of the other
正解：A
解説：
Explanation
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
質問 # 22
Which of the following parameters is not considered when restoring an LSP?
- A. Equipment vendor
- B. Maximum latency
- C. Reservation priority
- D. Coloring
正解：A
解説：
Explanation
The equipment vendor is not a parameter that is considered when restoring an LSP. Restoration is the process of re-establishing an LSP after a failure by using an alternative path that meets the same constraints as the original LSP. The parameters that are considered when restoring an LSP include coloring, reservation priority, maximum latency, bandwidth, protection type, and other QoS attributes. The equipment vendor does not affect the restoration process as long as the nodes support GMPLS protocols and interoperate with each other. References : RFC 4427 - Recovery (Protection and Restoration) Terminology for Generalized Multi-Protocol Label Switching (GMPLS), [Nokia GMPLS-controlled Optical Networks Course | Nokia]
質問 # 23
How is the GMRE functionality guaranteed in Nokia equipment?
- A. Redundant LAN cables guarantee GMRE functionality
- B. Controller redundancy guarantees GMRE functionality
- C. Rack redundancy guarantees GMRE functionality in case of a power outage
- D. The specific software configuration guarantees GMRE functionality
正解：B
解説：
Explanation
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
質問 # 24
A network with ROADM GMPLS nodes and optical transponder connections could have:
- A. L1 restoration capabilities
- B. No restoration capabilities
- C. L0 and LI restoration capabilities
- D. L0 restoration capabilities
正解：C
解説：
Explanation
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
質問 # 25
What is a Label Switched Path (LSP)?
- A. A protocol used by nodes to exchange information about the state of labels
- B. A switched protection path
- C. The path created by MPLS nodes
- D. A High Order Container for client signal
正解：C
解説：
Explanation
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
質問 # 26
How do you configure the Trail template in NFM-T for an Uplink board (such as 2UC400) in an MRN network with LO and LI restoration capabilities?
- A. Uncheck the Logical Link box Set the Port Type to Terminated Check the ASON Routed box Check the ASON Tunnel box
- B. Check the Logical Link box
Set the Port Type to Unterminated Check the ASON Routed box Check the ASON Tunnel box - C. Uncheck the Logical Link box Set the Port Type to Terminated Check the ASON Routed box Uncheck the ASON Tunnel box
- D. Check the Logical Link box
Set the Port Type to Unterminated Check the ASON Routed box Uncheck the ASON Tunnel box
正解：D
解説：
Explanation
To configure the Trail template in NFM-T for an Uplink board (such as 2UC400) in an MRN network with LO and LI restoration capabilities, you need to check the Logical Link box, set the Port Type to Unterminated, check 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 LO or LI restoration. The logical link is not terminated at the Uplink board, but at the OTU board. The ASON Routed option enables the GMPLS control plane for the logical link, while 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
質問 # 27
How are L0 and L1 resources coordinated in case of a failure in an MRN?
- A. Coordination is achieved by setting the color constraints
- B. Coordination is achieved by setting the WSR parameter
- C. Coordination is achieved by segregation of color and colorless LSPs
- D. Coordination is achieved by comparing the Setup Priorities
正解：A
解説：
Explanation
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
質問 # 28
What is the definition of Constrained Shortest Path First (CSPF)?
- A. It is the SPF algorithm applied for low latency LSPs.
- B. It is a combination between OSPF-TE and RSVP-TE.
- C. It is the 5FP algorithm applied after pruning links that do not meet the specified constraints.
- D. It is the SPF algorithm applied to low bandwidth LSPs.
正解：C
解説：
Explanation
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
質問 # 29
Which of the following statements best describes a distributed control plane for GMPLS?
- A. The network is managed by more than one network management system.
- B. The network manager controls all the routing for the network.
- C. The control plane is active in some network nodes and not in others.
- D. Each router has software to run the GMPLS protocols and can modify the node's switching fabric.
正解：D
解説：
Explanation
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
質問 # 30
What is the function of the OSPF-TE protocol?
- A. To monitor the availability of the links interconnecting adjacent nodes
- B. To assign different priority to various types of transported signals
- C. To exchange with other nodes data about the state of links
- D. To create an MPLS tunnel between two or more end points
正解：C
解説：
Explanation
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
質問 # 31
Which of the following statements about the Wait for Server Restoration (WSR) parameter in the MRN is correct?
- A. When WSR is false, the LI services do not wait for the LO restoration and restore through LI switching.
- 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 optical channel remains in the link until the failure is fixed.
- D. When WSR is true, the LO channels do not wait for the LI services to restore.
正解：A
解説：
Explanation
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
質問 # 32
Which of the following is not a key feature of GMPLS?
- A. Restoration
- B. Fast protection
- C. Resource optimization
- D. Self-discovery
正解：C
解説：
Explanation
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
質問 # 33
What is the GMRE node address?
- A. The IP address for communication between NEs
- B. An IP address for CORBA communication with the NMS
- C. The OSPF-TE broadcast IP used to flood the link adjacency information
- D. The LMP Control Channel ID. This field contains the IPv4 address of the ingress LER as a global unique identifier
正解：A
解説：
Explanation
The GMRE node address is the IP address for communication between network elements (NEs) in a GMPLS-controlled optical network. The GMRE node address is also known as the GMRE loopback address or the GMPLS node IP. It is used by GMPLS protocols such as LMP and RSVP to identify and communicate with other GMRE nodes. The GMRE node address is configured on each NE and is advertised by OSPF-TE to other nodes in the same area. References : Nokia 1830 PSS-4, PSS-8, PSS-16 and PSS-32 Platforms - NATO, 1830 PSS Identifiers
質問 # 34
What is Tunnel Property Heritage?
- A. Cost, SRLG, and Color properties are propagated from HO to LO LSPs.
- B. Maximum allowed bandwith is propagated from HO to LO LSPs.
- C. The hierarchy tunnels cannot be nested unless they share the same properties.
- D. A restored tunnel inherits the ODUk flows.
正解：A
解説：
Explanation
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
質問 # 35
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