Content-aware load-balancing solutions can provide the ability to drill deeper than ever before into HTTP requests and use the information in them to make decisions about where to direct traffic. Even a simple cookie-based solution can provide a load-balancer with additional information on which to base its choice of server. All that is left is to direct those high-dollar transactions to whichever server the engineers call "El Speedy" and complete transactions faster than ever -- all without radically modifying your existing e-business infrastructure. With Layer 7, or content-aware, load-balancing devices, you can achieve this type of functionality without completely reworking your e-business infrastructure.

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The concern when using Layer 7-based load-balancing is that performance will degrade. And while our testing of five solutions proved that this is generally true, we found that the real question is how much will performance degrade (see "Performance of Load-Balancers" below).

But performance isn't everything. Scalability requires that changes to the farm -- whether adding new servers or altering logic -- be made as painlessly as possible and without interruption to services. A good management and configuration interface will provide the ability to perform these tasks. Whether via a CLI (command-line interface) or GUI, performed locally or remotely, the ability to configure, maintain and monitor your server farm is essential to your e-business infrastructure.

In the e-business world, stateful failover features are more important than ever. Load-balancing devices almost always provide a method of failover -- a secondary unit waiting in the wings to take over if the primary should fail. But what happens to the sessions stored in the primary device when the secondary device takes over? Stateful failover solves this problem. New load-balancing devices mirror sessions -- passing session information to the secondary unit (or to the primary unit in an active-active configuration) at specified intervals. This ensures that even in the event of a load-balancing device failure, most of the sessions will be maintained as the secondary device takes over for the failed primary unit.

And if you're looking for a Layer 7-based load-balancing solution, you certainly need to examine the logic of each product. You'll want to know how rules are created and what information you can base your switching decisions on.

To the Test

In our partner lab at Schneider National, in Green Bay, Wis., we put Alteon WebSystems (now owned by Nortel Networks) AceDirector 4, Radware's Web Server Director Pro, CyberIQ Systems' HyperCommerce, F5 Networks' Big-IP HA+ Controller 3.3 and HydraWeb's Hydra2500 to the test. We also invited Foundry Networks to participate, but it declined, citing a lack of available resources. Foundry resells F5's Big-IP as well.

We invited, cajoled and pleaded, but we could not convince Cisco Systems to participate in this review. All our efforts were met by a stone wall -- with no explanation offered. Intel was invited but declined to participate on the basis that its product is an appliance rather than a switch. Interestingly, the company took part in our review last summer against some of the same vendors that participate here (see "Web Content Switching").

During testing we noticed a couple of new trends. Two products offer the ability to heavily customize load-balancing algorithms to provide better scalability and availability of back-end servers. Whether it's done via a proprietary method or good old SNMP, this feature is definitely appealing. The second interesting feature among these load-balancing solutions is integrated bandwidth-management capabilities. Two of the products we tested offer this capability. Bandwidth management is a complementary technology that only adds to the appeal of a load-balancing solution. With it, you can control the traffic coming in as well as how it is distributed to back-end servers.

Lighting a Fire

We examined the administrative and configuration methods of all the products in our test, especially in the area of building and maintaining clusters. Our performance tests were designed to find any degradation between two possible solutions -- one that used ports to distinguish between customers and the other with Layer 7-based features. Our test transaction comprised four objects (three images and one text file) for a total of 24 KB of data. We loaded up 15 Dell Computer Corp. workstations with RadView Software's WebLoad 4.0 to generate a set of tests ranging from 750 to 2,000 clients.

We ran three sets of tests for each configuration -- the first using 750 clients, then 1,500 clients and finally 2,000 clients. We got a good view of configuration and management while setting up each product for the tests.

Radware's Web Server Director Pro squeaked by both Alteon WebSystems AceDirector 4 (AD4) and F5's Big-IP HA+ Controller to take our Editor's Choice award. Radware's ConfigWare application made configuration and management effortless. Not only is Web Server Director Pro robust and intuitive, but it also offers multiple views of your servers. The ability to customize your own load-balancing algorithms based on SNMP values gives it the edge to home the prize. AceDirector and Big-IP HA+ Controller tied for second in our testing.

The Big-IP HA+ Controller offers spectacular logic and a great price. The only place it fell down was in its GUI-based configuration software. Improving this might give it the win next time. Big-IP's Web-based GUI tool has a confusing layout that caused us to make mistakes during configuration.

While AceDirector performs over and above the competition and its easy-to-configure WebOS 8.0 is a dream, we had to take into consideration switching logic as well. The AceDirector's logic is still behind the Web Server Director Pro's. Just a bit more maturity in AceDirector's Layer 7 switching options would have given it the lead.

Our final two products came in well behind the leaders. Configuring HydraWeb's Hydra2500 left our heads spinning around faster than Linda Blair's. However, the product does provide a rich logic set at an acceptable price. The product offers only two load-balancing algorithms -- a highly configurable proprietary system as well as round-robin. But its lack of gigabit interfaces -- the AceDirector, Big-IP HA+ Controller and Web Server Director Pro all offer at least two Gigabit Ethernet interfaces -- is problematic.

CyberIQ Systems' HyperCommerce has a lot of work to do to be a contender. Its support of only cookies and SSL session ID at Layer 7 is one reason the HyperCommerce took last place. Management and monitoring functionality is also lacking when compared with those of its competitors. And without gigabit interfaces, this product gives us little to be excited about.

Build for the Future

Going back to our entrepreneurs, the third little pig built a high-availability e-business infrastructure by examining not only what he needs today, but what he would need to support a growing e-business in the future. His brothers built for today -- and as so many dot-com ventures are finding out, this tactic is a recipe for failure. If the first two little pigs had patience and invested in their e-business infrastructure, they may have been able to handle the demands of their customers and business partners.