In a sense, load balancers operate on different layers.
Layer 4 load balancers forward traffic based on data found in network packets, such as source and destination IP addresses and port numbers. This type of load balancer is often used for forwarding traffic to a specific server or group of servers.
Layer 7 load balancers make forwarding decisions based on data found in application layer protocols such as HTTP and HTTPS. This allows the load balancer to make more intelligent decisions about where to send traffic, such as sending all requests for a certain website to the same server.
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