Abstract: Aiming at the problem of data centers difficulty in adapting to traffic growth for horizontal expansion and ensuring connection consistency, this paper explains the important role of layer-4 load balancing technology in coping with high concurrent access and improving resource utilization, and sorts out four-layer load balancing modules domestic and international. The advantages and disadvantages of load balancers deployed in different ways are summarized, and the application and latest development of network programmable forwarding technology in the field of layer-4 load balancing are analyzed. Finally, The development of load balancing technology under the new network situation is further prospected and future research directions are discussed.

Key words: data center, load balancing, connection consistency, programmable forwarding technology