Load Balancing Basic Concepts

Before using Zevenet load balancing solutions, we are going to learn the load balancing basic concepts for getting an overview of the load balancing technology.

Farm is a set of servers which offers the same service over a single one entry point defined with an IP address and a port, a single IP address or a network interface; which is commonly called virtual service. The main farm task is to provide to the clients a direct access to the service in a transparent mode and taking care the persistence and other connection properties. Additionally, the farm definition establishes the delivery policies to every real server.

“Farm” is one of the main Load Balancing basic concepts because distributes the load among the backends.

Backend is a server that offers the real service over a farm definition and it processes all the real data requested by the client.

“Backend” is one of the main Load Balancing basic concepts because is a real server, transforming requests into responses, only makes sense to have more than one so the requests can be balanced.

Client is called to the source IP address which connects to the load balancer virtual service and it’s usually initiated by an user request or remote process. Several users or client processes could be identified by the same IP address.

“Client” is one of the main Load Balancing basic concepts because is where the balanced requests are coming from.

Application Session is a layer 7 concept which tries to identify a single user request although several clients share the same IP client address.

“Application Session” is one of the main Load Balancing basic concepts because the requests of the same session can be directed to the same backend, so some application requirements like authentication can be persistent. If a authenticated session is opened in a backend and another request is sent to a different backend, because the client is not authenticated on the second backend, the request will not be processed.

Real IP is a physical IP address defined over a network configuration which is assigned to a server or NIC.

“Real IP” is one of the main Load Balancing basic concepts because is the IP address of a backend, also known as a real server.

Virtual IP is a floating IP address over a network configuration which is used to be the entry point of a virtual service defined by a farm that is ready to deliver connections between redundant load balancing nodes.

“Virtual IP” is one of the main Load Balancing basic concepts because is the IP address of a Farm, the client does not know the IP of any backend, only the IP used by a Farm so the service can be balanced between backends through the Farm.

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