The operations team plans to migrate the core to Segment Routing (SR‑MPLS) for LSP steering. Which legacy control‑plane protocol can be safely removed in an SR‑MPLS core for label distribution?
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Correct answer: LDP.
Why this is the answer
LDP (Label Distribution Protocol) is used in traditional MPLS to distribute labels for IP prefixes. In an SR-MPLS (Segment Routing with MPLS data plane) core, label distribution for forwarding is handled by the IGP (like OSPF or ISIS) which advertises segment identifiers (SIDs). These SIDs serve as the labels, eliminating the need for a separate label distribution protocol like LDP. Therefore, LDP can be safely removed. OSPF is an IGP and is essential for routing information. RSVP-TE is used for traffic engineering with explicit paths and is not directly replaced by SR-MPLS's core label distribution. BGP is used for inter-domain routing and VPN services, not for core label distribution for IGP prefixes.
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