When using Alibaba Cloud SLB, users can enable the health check function. Layer-4 SLBs (TCP protocol) determine the availability of ECS instances through_____________. (Single answer)

When using Alibaba Cloud SLB, users can enable the health check function. Layer-4 SLBs (TCP protocol) determine the availability of ECS instances through_____________. (Single answer)
A . Whether the 3-way handshake can be established between the backend ECS instance and the SLB
B . Special characters contained in the message returned from backend ECS instances
C . Status codes returned from backend ECS instances
D . Length of message returned from backend ECS instances

View Answer

Answer: A