F5 Networks BIG-IP 6800
Very Good  8.5
Bottom Line: The BIG-IP 6800 is an extremely capable load balancer and Web application optimization engine. It should be scalable enough for even the largest Web application, and offers a depth and breadth of features difficult to equal. Functions such as application firewalling and global load balancing come at additional cost.

Juniper DX3680 v. 5.2
Excellent  8.7
Bottom Line: The DX3680 is an example of the adage "you get what you pay for." It's a very capable 2U appliance that not only creates clusters of Web servers but also adds SSL encryption, user authentication, and protection against hacker attacks. All of this is done transparently without having to rewrite HTML code on the Web servers. The application rules functionality provides powerful customization capabilities as well.

Kemp Load Master 1500 Version 4.1-33
Good  7.7
Bottom Line: Although initial setup is a bit of a pain, the wide variety of preset options in the Kemp Load Master make configuring persistence or sophisticated health checks easier than usual. The GUI is clear and easy to navigate, and drop-down menus handle functions that require creating scripts or custom rules in other products. The Load Master goes a step beyond the Barracuda at a slightly higher price.

Zeus ZXTM 7000 4.0r1
Very Good  8.4
Bottom Line: The ZXTM 7000 offers a wide variety of features beyond the standard load balancing, and it’s easily expanded as needed. Although not quite as powerful or polished as competitors such as the BIG-IP, it is nevertheless easy to set up and manage, and it can be scaled by clustering up to 64 units.

How I tested
To test the performance of each product, I set up several servers with the same Web site (a demo version of an e-commerce site) and created a virtual cluster with those servers in it. The servers varied in processor number and power. I then used an Ixia 400T traffic generator and Aptixia IxLoad software to simulate a large number of users accessing the Web site, and compared the loads generated on each server. I then enabled features such as SSL sessions, Web acceleration, and application security, and attempted to overload the load balancer by simulating many simultaneous users.

Testing the Web application acceleration features of the products is more problematic. The greatest improvements in delivery of pages from the Web servers will occur when the server is heavily loaded (or would be heavily loaded if the load balancer weren’t present. The type of content being delivered also makes a big difference – static HTML pages will see big improvements while dynamic pages using .ASP, CGI, Java, or other application servers may not seem much faster. The performance of the server delivering the application will be the gating factor rather than network performance.