Despite its management and configuration shortcomings, BIG/ip³ has some important features. Securing your Web site and your Web load balancer makes good sense. Features like its configuration synchronization tools, combined with superb performance, make BIG/ip³ worthy of consideration for both Internet and intranet sites.

Resonate Central Dispatch 2.11
Last year, we evaluated an early beta of the software load balancer Resonate Central Dispatch (RCD). In its more recent version, we found improvements in its management software, installation and overall look and feel. Its real-time monitoring tools are second to none, with graphs and node information. Other features, such as URL-based load balancing and the InSite testing tool, make it a distinctive and strong performer, and perhaps a suitable alternative to proprietary hardware-based solutions.

RCD's URL-based load balancing, based on incoming HTTP requests, allows administrators to place server power where it's needed most. For example, using the URL-based load balancing feature, we configured our test cluster to load balance our CPU-intensive CGI scripts onto a robust Pentium II server with 512 MB of RAM. All other content was balanced over the rest of the cluster. This ensured that visitors to our test cluster would receive prompt responses from any CGI scripts. Bright Tiger ClusterCATS is the only other load balancer we tested that can handle this scenario, but RCD does a much better job than the ClusterCATS' DNS/redirect load balancing.

Unlike ClusterCATS, RCD is a TCP/IP load balancer and can handle any TCP/IP service. Rules are made to determine what services are balanced where and at what thresholds. All of this information can be viewed and changed using the Dispatch Manager, a standalone Java GUI management program that can run anywhere on the network. RCD currently supports Solaris and Windows NT platforms; an HP-UX version is expected soon.

RCD pricing depends on the number of servers you have for your Web site and how powerful they are. Multiprocessor machines cost more than single-processor machines, and Solaris-based server pricing varies from that of Windows NT servers.

Dispatch Manager includes the most complete real-time monitoring tools. Administrators can monitor open connections and hits per second for both server nodes and aggregate clusters. Server nodes are also polled for network latency. RCD is much more comprehensive and has more features than ClusterCATS, LocalDirector and BIG/ip³; however, it's hurt by less-than-desirable performance numbers.

Bright Tiger Technologies Bright Tiger ClusterCATS 1.1
The ClusterCATS (Content, Application and Transactions Smart) software load balancer, another newcomer to the field, has many notable configuration and management features. But despite its time-savers, including content replication and real-time monitoring tools, we found ClusterCATS to be severely lacking for deployment in an enterprise environment. As impressed as we were by its many intuitive features, we did not like the mandated use of Microsoft Corp.'s Internet Information Server (IIS) 2.0 (or above) and Windows NT. We also found ClusterCATS' failover and load-balancing mechanisms inadequate for an enterprise environment.

The most important thing to know about ClusterCATS is that it relies on round-robin DNS to load balance servers. When a user requests Web content, the server will handle the request only when it is functioning in the "nonbusy" state. Servers are "busy" whenever the HTTP response time exceeds a configured value.

Although this may result in suboptimal response times--particularly when a specific server is very busy--it is an effective means of load balancing. Its weakness is that the server has no control over new Web requests and must deal with them constantly. ClusterCATS is much less efficient in its load-balancing algorithms than all the hardware load balancers we tested.