Azure Application Gateway is a web traffic load balancer that can be used to manage traffic to web applications. This web traffic load balancer operates at the application layer (Layer 7 in the OSI network reference stack).
It offers web load balancing, which is for HTTP(S) only. Traditional load balancers operate at the transport layer (Layer 4 in the OSI network reference stack), and route traffic—based on the source IP address and a port number—to a destination IP address and a port number. With Azure Application Gateway, traffic can be routed based on the incoming URL as well. For instance, if /pictures is part of the incoming URL, traffic can be routed to a particular set of servers that have been specifically configured for pictures. If /audio is part of the incoming URL, the traffic is routed to another set of servers, configured specifically for audio files. The following diagram shows the workflow of Azure Application Gateway...