Introduction to F5 load balancer tool.

What is the purpose of an f5 load balancer?
F5 Networks, Inc. is a company that has developed and manufactures products including load balancers. Load balancers are a mechanism for making an application tier redundant and available even during hardware failures of single servers,
A local server load balancer will distribute the load between a pool of application servers, such as a web server. The load balancer has an IP address that client computers, like web browsers, will send requests. The load balancer has different options for what method to determine which server to send the session to. For example, the load balancer can track how many concurrent sessions each server has and will send the next new session to the server with the least connections, ergo least connections is one method,

The load balancer also polls each of the servers and if one stops responding, the load balancer will stop sending traffic to the dead server,
Another aspect of load balancing is that some applications must “stick” the client connects to the same server for the duration of its communication. The load balancer can make certain that persistence or “sticky” does this.
F5 and other manufacturers of load balancers also make global site load balancers that redirect domain name service (DNS) between geographic locations, whereas local site load balancing redirects IP addresses.

Load Balancer
A load balancer is a device that acts as a reverse proxy and distributes network or application traffic across a number of servers. Load balancers are used to increase capacity (concurrent users) and reliability of applications. They improve the overall performance of applications by decreasing the burden on servers associated with managing and maintaining application and network sessions, as well as by performing application-specific tasks.  

Load balancers are generally grouped into two categories: Layer 4 and Layer 7. Layer 4 load balancers act upon data found in network and transport layer protocols (IP, TCP, FTP, UDP). Layer 7 load balancers distribute requests based upon data found in application layer protocols such as HTTP.
Requests are received by both types of load balancers and they are distributed to a particular server based on a configured algorithm. Some industry-standard algorithms are:

• Round robin
• Weighted round-robin
• Least connections
• Least response time
  

Load Balancer - F5 Networks

Layer 7 load balancers can further distribute requests based on application-specific data such as HTTP headers, cookies, or data within the application message itself, such as the value of a specific parameter.
Load balancers ensure reliability and availability by monitoring the "health" of applications and only sending requests to servers and applications that can respond in a timely manner.