When studying layer 4 load balancing it is natural to also compare the Layer 7 load balancing options as well. Layer 4 load balancing is relatively simple while layer 7 load balancing is far more complex. For this reason while Layer 4 load balancers are normally available free of charge and at the same time they are extremely good at what they do, load balancers that combine Layer 4 and Layer 7 load balancing are far more complex and for this reason you need to prepare to purchase them as they are not available as free ware.
Layer 4 load balancing defined
One of the best known Layer 4 load balancers is Microsoft Network Load Balancer or NLB, this is a core network load balancer software that is available to users of mission critical Microsoft applications including Microsoft Exchange and Microsoft OCS the unified communications platform. Like other Layer 4 load balancer solutions it is fairly simple. Most layer 4 load balancers perform the following functions:
- Load balances at a simple level and directs traffic based on server response time
- Each server shares the same IP address
- The least busy server responds to the content demand
- Round Robin DNS is extensively used
Layer 7 load balancing is more complex but far more efficient
Layer 7 load balancing is effectively ruled by directing the traffic according to the application that is being used.
So the servers are divided up and used based on their specialization to deliver:
- PHP applications
- Java content
- Rich graphic content
Each task here can be allocated to a different server and this is different to Layer 4 load balancing where replication is the key. At Kemp we have combined the simplicity of Layer 4 load balancing with the content sensitive and rich options offered by layer 7 load balancing and delivered these combined in a way to get the best from both platforms.
User experience is key to us and making it easier to have a “great user experience” is our goal by making complex decisions simple, at Kemp that is what we do.