What is the function of a TLOC extension interface?

A TLOC extension interface allows a WAN Edge router to utilize the transport network (e.g., MPLS, Internet) connected to a neighboring WAN Edge router. This is particularly useful in scenarios where one router might not have direct connectivity to all available transports, or to provide redundancy. Instead of forming its own direct connection to a transport, it "extends" its TLOC over to its neighbor's transport. The other options are incorrect: "gives access to business Internet" is too specific; TLOC extensions work with any transport, not just the Internet. "forms an alternate connection to connected transport" is vague and doesn't capture the essence of extending to a neighbor's transport. "synchronizes the configuration with the neighboring WAN Edge router" describes a control plane function, not a data plane connectivity mechanism like TLOC extension.