Kakao Reveals DSCP-Based L3DSR Load Balancing Configuration for Multi-IDC Environments

Kakao uses a DSCP-based L3DSR (Layer 3 Direct Server Return) configuration to perform load balancing without physical location constraints on servers in multi-IDC environments. While the existing L2DSR had the physical limitation that the server and ADC had to be in the same broadcast domain to change the MAC address, L3DSR overcomes this by modifying the IP header. The server sets the VIP on the Loopback Interface (lo:0) to prevent dropping packets where the Destination IP is the VIP, and allows only requests with the same DSCP value (e.g., 10) as the LB equipment via IPTABLES. For load distribution, it uses Round Robin to avoid the drawback of Least Connection, where traffic concentrates when new servers are introduced, and primarily utilizes L7 Health Check to verify normal application operation, ensuring service stability.