Which of the following descriptions of the railway business network security and reliability requirements are incorrect?

Which of the following descriptions of the railway business network security and reliability requirements are incorrect?
A . TDM services and Ethernet services are physically isolated using different hard pipes
B . Different Ethernet subsystems use ODUk physical pipes to isolate services
C . E1 services are on the TDM plane, and IP services are on the packet plane. The encapsulation and forwarding efficiency of the two types of services are optimized.
D . Business connections tend to be IP-based, so physical isolation of business is no longer required

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Answer: D