Regarding the processing mode of MPLS for TTL, which of the following description is correct?
A . In the Pipe mode, when an IP packet passes through the MPLS network, the IP TTL is decremented by 1 to the MPLS TTL field in the ingress node.
B . The TTL of the MPLS label has the same meaning as the TTL in the IP header, which can prevent the MPLS network from generating a routing loop (according to the reason A)
C . Uniform simulation, when the IP packet passes through the MPLS network, the IP TTL of the ingress node is decremented by 1, and the MPLS TTL field is a fixed value.
D . In MPLS VPN, if you want to hide the structure of the MPLS backbone network, you can use the uniform mode in Ingress for private network packets.
Answer: B