Key details for this exam, checked against the published exam outline
Each question shows the correct answer and an explanation of why it is right
A network architect is designing an optical transport network that will use GMPLS to automate lightpath provisioning. During the design review, a colleague asks what fundamental capability the GMPLS control plane adds compared to a purely NMS-driven provisioning model. Which statement best answers this question?
The GMPLS control plane extends MPLS traffic engineering concepts to non-packet technologies (TDM, lambda, fiber switching), enabling distributed signaling (RSVP-TE) and routing (OSPF-TE) protocols to run between network elements so that connections can be dynamically discovered, computed, signaled, and restored without manual per-node provisioning. The other options misstate GMPLS's role: it does not replace the data plane, it does not eliminate dynamic routing, and it is specifically designed to extend control to non-packet (optical/TDM) switching, not exclude it.
An engineer is troubleshooting why two neighboring optical nodes in a GMPLS network fail to exchange traffic engineering link-state information, even though the control channel is up. The engineer confirms that RSVP-TE signaling works correctly for existing connections, but no new topology updates are being learned. Which protocol is most likely misconfigured or down?
OSPF-TE is the routing protocol extension responsible for distributing traffic engineering link-state information (bandwidth, link attributes, topology) between GMPLS nodes. If RSVP-TE signaling still functions for existing LSPs but no new topology/link-state updates are learned, the issue points to the routing protocol (OSPF-TE), not the signaling protocol. LMP manages control channel and link verification but is not primarily responsible for TE topology distribution, and SNMP is a management protocol, not part of the GMPLS control plane routing/signaling stack.
A service provider requires that, in the event of a fiber cut, traffic on a critical wavelength service be restored within tens of milliseconds using a pre-computed and pre-signaled backup path that is not carrying traffic under normal conditions. Which mechanism best meets this requirement?
1+1 or 1:1 protection schemes pre-establish and pre-signal a dedicated backup path (or bridge traffic simultaneously in 1+1) so that switchover occurs almost instantaneously upon failure detection, meeting stringent sub-100ms restoration requirements. Restoration approaches, by contrast, compute and signal the backup path only after failure is detected, which takes longer (typically hundreds of milliseconds to seconds) due to path computation and signaling overhead. Manual NMS re-provisioning is far too slow for this use case.
In a GMPLS-controlled network, an operator wants a failed connection to be restored using a newly computed path that had not been pre-signaled prior to the failure, since bandwidth availability changes frequently and pre-reserving backup capacity is not cost-effective. Which recovery approach is being described?
Restoration is the recovery mechanism in which the backup path is computed and signaled dynamically after a failure is detected, rather than being pre-established. This approach is more resource-efficient because backup capacity is not permanently reserved, but it incurs longer recovery times than protection schemes. Protection mechanisms like 1+1, linear protection, and SNCP all rely on a pre-computed and often pre-signaled backup path, which contradicts the scenario's requirement of dynamic, on-demand path computation.
A network operations team performs regular audits of a GMPLS-controlled optical network to verify that the control plane's view of active LSPs and link resources matches the actual state of the data plane, in order to catch database inconsistencies before they cause provisioning failures.
This type of routine verification activity is an example of which category of GMPLS network management?
Ongoing tasks such as auditing control plane databases against the actual data plane state, verifying resource consistency, and performing routine health checks fall under GMPLS maintenance and operations. These day-to-day activities ensure long-term network stability and correctness of automated provisioning, distinct from the initial architectural design of the control plane, the definition of signaling protocols themselves, or physical installation work, all of which are separate phases or topics.
40 questions covering all exam domains, starting from $20
Exam domains verified against: Official Nokia 4A0-220 exam guide, last checked September 2026.
Introduces the overall purpose and structure of the course. Outlines the key areas that will be covered across the modules. Sets expectations for the skills to be gained by the end of the course.
Explains the basic concept of the GMPLS Control Plane. Describes the architectural components involved in GMPLS. Covers how the control plane fits into optical network design.
Sample question from this domain above: Q1
Covers the protocols used to enable GMPLS functionality. Explains how signaling and routing are handled within GMPLS. Describes the role of protocols in supporting control plane operations.
Sample question from this domain above: Q2
Explains mechanisms used to protect network traffic. Covers restoration processes used after a network failure. Describes how protection and restoration maintain service continuity.
Covers day-to-day operational tasks for GMPLS networks. Explains maintenance procedures to ensure network stability. Describes how operations are managed within a GMPLS-controlled environment.
Sample question from this domain above: Q5
Common questions about the exam itself
