Quick Answer
The correct answer is the Segment Routing Path Computation Element (SR-PCE) architecture. This is because the scenario explicitly describes a centralized controller that computes paths based on traffic demand and network constraints, which is the precise function of a Path Computation Element. In Segment Routing, the SR-PCE acts as this centralized controller, using traffic engineering constraints to calculate optimal paths and then communicating those paths to the headend router via the Path Computation Element Protocol (PCEP). On the Cisco SPCOR 350-501 exam, this question tests your ability to distinguish between centralized and distributed control plane models—a common trap is confusing SR-TE (the overall traffic engineering mechanism) with the specific centralized controller architecture itself. Remember the key: if the question mentions a centralized controller computing paths, think PCE. A useful memory tip is "PCE = Path Computation Engine," the brain that does the math, while the headend just follows orders.
This 350-501 practice question tests your understanding of architecture. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network operator is deploying segment routing in an MPLS network. They want to use a centralized controller to compute paths based on traffic demand and network constraints. Which architecture is being used?
LDP-based MPLS
Why wrong: LDP is distributed, not centralized.
Segment Routing Traffic Engineering (SR-TE)
Why wrong: SR-TE can use a controller but is not specifically an architecture name.
Segment Routing Path Computation Element (SR-PCE)
SR-PCE is a centralized controller for path computation.
Segment Routing Best Effort (SR-BE)
Why wrong: SR-BE does not use a centralized controller.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Segment Routing Path Computation Element (SR-PCE)
The scenario describes a centralized controller computing paths based on traffic demand and network constraints, which is the definition of a Path Computation Element (PCE) architecture. In Segment Routing, the SR-PCE (Segment Routing Path Computation Element) is the centralized controller that calculates optimal paths using traffic engineering constraints and then communicates the path information (via PCEP) to the headend router. This is distinct from distributed control plane approaches like LDP or SR-BE, and from SR-TE which is the overall traffic engineering mechanism but not the specific centralized controller architecture.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
LDP-based MPLS
Why it's wrong here
LDP is distributed, not centralized.
Segment Routing Traffic Engineering (SR-TE)
Why it's wrong here
SR-TE can use a controller but is not specifically an architecture name.
Segment Routing Path Computation Element (SR-PCE)
Why this is correct
SR-PCE is a centralized controller for path computation.
Related concept
Read the scenario before looking for a memorised answer.
Segment Routing Best Effort (SR-BE)
Why it's wrong here
SR-BE does not use a centralized controller.
Common exam traps
Cisco often tests the distinction between the overall traffic engineering mechanism (SR-TE) and the specific centralized controller architecture (SR-PCE), leading candidates to pick SR-TE when the question explicitly mentions a 'centralized controller' for path computation.
Detailed technical explanation
The SR-PCE architecture leverages the Path Computation Element Protocol (PCEP, RFC 5440) to communicate computed paths to the headend router, which then installs a segment list (label stack) for SR-TE tunnels. A key subtlety is that the PCE can be stateful, maintaining the state of all LSPs in the network to avoid double-booked bandwidth and to optimize globally. In real-world deployments, SR-PCE is often combined with BGP-LS (Link State) to collect network topology and TE metrics, enabling constraint-based path computation like avoiding certain links or meeting latency requirements.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Architecture — This question tests Architecture — Read the scenario before looking for a memorised answer..
The correct answer is: Segment Routing Path Computation Element (SR-PCE) — The scenario describes a centralized controller computing paths based on traffic demand and network constraints, which is the definition of a Path Computation Element (PCE) architecture. In Segment Routing, the SR-PCE (Segment Routing Path Computation Element) is the centralized controller that calculates optimal paths using traffic engineering constraints and then communicates the path information (via PCEP) to the headend router. This is distinct from distributed control plane approaches like LDP or SR-BE, and from SR-TE which is the overall traffic engineering mechanism but not the specific centralized controller architecture.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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