By using load balancing technology, Combell distributes the workload of your servers optimally across your server farm. This way, we make sure that your infrastructure is as ready as possible to support your business.
The actual distribution of the workload can be performed on the different layers of the OSI model. Depending on the layer where the load balancing is performed, another type of load balancer is required. There are thus several methods for load balancing: the load balancer distributes the load of the servers on the level of the network (layer 3 in the OSI model), on the level of the application layer (layer 7 in the OSI model) or on the level of the application combined to SSL.
Simply put, you could compare load balancing to the proceedings of traditional postal mail. A layer 3 load balancer that works on network level acts as the mailman who delivers a letter to the address of a company.
This is how the load balancer distributes workload over the different servers, simply by means of the IP address. Load balancing on application level - on layer 7 - goes one step beyond and distributes the workload over the servers in accordance with the content of the application itself. Thus, layer 7 load balancers are intelligent. Let us compare the system with a traditional letter again. With a layer 7 load balancer, the mailman opens the letters and distributes them in accordance with their content: all letters on white stationary get a specific destination, the same goes for all hand-written letters, etc. The benefit of a layer 7 load balancer is that, thanks to the built-in intelligence, it is able to distribute the load far more accurately over the available systems.
The combination of load balancing on application level with SSL does basically the same thing, but with added security.
The letter is then contained in an encrypted envelope. Only when the load balancer has the correct key at its disposal, can it further perform the task.
Basing itself on open source products, Combell has developed a layer 3 load balancer of its own, that works on network level. For layer 7 load balancing, Combell works with products of, among other brands, Cisco and F5.