Link Load balancer is to distribute internal network request toward multiple ISP lines for:
- Fast Internet Access
- WAN Load Balancing
- WAN Link Bonding
- 100% Internet Uptime with Automatic Failover
- Application Access Prioritization
Network Load Balancer is to distribute incoming network request across multiple servers in a server farm which operates at layer 3/4 of the OSI model.
Application Load Balancer (also known as Server Load Balancer) is quite similar to Network Load Balancer but operates at layer 7 of the OSI model and offer wider range of routing rules based on traffic content type, cookie data, custom headers, user location, or the application behavior.