F3215-HP Load Balancing Module Load Balancing Configuration Guide-6PW101

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Figure 6 Work flow of Layer 7 server load balancing
Layer 7 server load balancing operates in the following way:
Step 1 through 3—Host and the LB module establish a TCP connection.
4. Host sends a service request, using VSIP as the destination address.
5. Upon receiving the request, the LB module selects an appropriate server group for the request
according to a real service group method, uses an algorithm to calculate to which server in the
server group it distributes the request, and then caches the request.
6. The LB module sends an SYN packet to Server. The sequence number is the sequence number of
the SYN packet sequence number sent by the host.
7. Server sends an SYN ACK packet, using the destination IP as Host IP.
8. After receiving the SYN ACK packet, the LB module responds with an ACK packet.
9. The LB module changes the destination IP and TCP sequence number of the request cached at step
5, and sends them to Server.
10. Server sends a response to the LB module, using the destination IP as Host IP.
11. The LB module changes the source IP and TCP sequence number in the response, and sends them
to Host.