RS6500: Net Traffic Cop With a Mission

Appliance ably manages site use, but it's not for heavy-duty server chores.

NetScaler Inc.s RS6500 traffic management appliance can improve the performance and security of enterprise Web infrastructures without emptying the IT budget.

In eWeek Labs tests, the NetScaler RS6500, which shipped in November, integrated high-performance traffic management capabilities with hardware that gave our test Web site a significant performance boost.

The RS6500 runs on FreeBSD and is priced at $35,000 per high-availability pair, which is competitive with other Web traffic management appliances in its class. For example, F5 Networks Inc.s Big-IP 5000 IP application switches cost $32,000 each and $58,000 for a redundant pair, and Radware Inc.s Web Server Director Pro costs $24,500 for a stand-alone unit.

However, unlike the Big-IP 5000, the RS6500 doesnt have built-in SSL (Secure Sockets Layer) acceleration, nor does it have a switch fabric—it currently supports only two Gigabit Ethernet ports. NetScaler offers the RS6500 in a package with an SSL appliance, the RS6600, for $45,000, but for shops that want an application switch instead of a dedicated traffic manager, the Big-IP 5000 might be a better choice, offering built-in SSL along with multiple 10/100M-bps and Gigabit Ethernet ports.

The RS6500 comes in a compact 3.5-inch chassis housing a 1GHz Pentium processor, 1GB of RAM and dual Gigabit Ethernet ports. For sites that dont require all that horsepower, NetScaler offers less-expensive Ethernet models at prices ranging from $15,000 to $30,000 per pair.

In tests, the RS6500 provided robust server load balancing, content switching and cache redirection. Its surge protection feature can safeguard Web sites from debilitating traffic surges such as DoS (denial-of-service) attacks. The RS6500 appliance is also armed with NetScalers Request Switching Technology, which handles traffic management at the application-request level.

The idea behind RST is simple but effective: The RS6500 maintains a number of persistent HTTP 1.1 connections between clients and the Web server farm. The RS6500 manages the traffic through these connections by analyzing the requests and sending them to the appropriate Web server. The persistent connections are offloaded from the servers to the NetScaler appliance, so servers have more CPU cycles available.

Although the RS6500s server load balancer can greatly improve the performance of a site, it does not support multisite load balancing. Enterprise sites that want to balance traffic to mirror sites around the globe should look to the Big-IP 5000 or the WSD Pro. NetScaler is planning to offer multi-site server load balancing in the next release.

The RS6500 uses multiplexing techniques to fuse multiple client connections into a smaller number of persistent connections that the Web servers can handle more effectively, increasing the overall site performance.

The RS6500 supports Layer 7 Content Switching for sites that have dedicated servers for specific contents. The appliance will analyze the traffic based on the application-level protocol associated with the request and forward the request to the servers with the correct content.

This works best for sites that have dedicated Web servers or farms for specific services such as FTP, Network News Transfer Protocol or streaming media.

An Avalanche of Data

The NetScaler RS6500 performed well in tests using Caw Networks Inc.s WebAvalanche Web stress-testing appliance. We used WebAvalanche to subject the RS6500 to high loads of HTTP 1.0/1.1 requests, simulating the traffic generated by a large number of Web clients. At the back end, we used Caws WebReflector to gauge responses to the requests generated by WebAvalanche, simulating the behavior of Web server farms.

We set up a pool of 20 Web servers in a virtual test site and directed the WebAvalanche "clients" to the virtual IP address of the RS6500. The RS6500 did well in our test for maximum number of HTTP GET commands, delivering more than 20,000 transactions per second.

To test the RS6500s throughput, we used WebAvalanche to fetch large files from the WebReflector with the RS6500 in between. The RS6500 clocked close to 700M bps in these tests.

The RS6500 can be configured using the CLI (command-line interface), Secure Shell or Web-based GUI. Shops familiar with Unix should be able to set up the box fairly quickly using the CLI and configuration scripts. NetScaler provides a useful command reference for the CLI, and the GUI is straightforward—we set up the test configuration without problems —but we would like to see configuration wizards or utilities to make setup more intuitive for first-time users.

Technical Analyst Francis Chu can be reached at [email protected]