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NetScaler 3100: Ad Fast

By Karen J. Bannan & Rob Schenk
April 18, 2001

Web sites want their content to load quickly. Not surprisingly, companies that serve ads to Web pages want their content to load even fast er. At least, that's the view of Alfredo Botelho, founder and CTO of Zedo, a San Francisco-based Internet advertising firm.

Zedo provides targeted advertising to half a dozen medium-size gaming and chat Web sites and a women's interest portal, each with more than 100 million page views per month. To get visitors to click through while they wait for a page to load, ads need to load first. Botelho did two things to accomplish this. He added the NetScaler 3100 to his company's infrastructure and at the same time signed up f or Akamai's content distribution network to get the ads closer to end users.

The combination seems to be working.

Ads are loading up to four times as fast as before, which results in an increased number of click-throughs. "The fact that the ad comes up now way before the page's content is what we call prime-time advertising," says Botelho.

The process of adding the 3100 was simple, since NetScaler handled all the integration. The entire installation was completed in less than a day, and without any additional infrastructure upgrade to the Zedo network or servers.


The NetScaler 3100 ($20,000 list) is an appliance that sits in front of a Web site's server farm, providing strong scalability as well as protection against big surges in traffic.

The 3100 works by enabling persistent HTTP 1.1 connections between the back-end server infrastructure and itself. As external Web site requests are made, the 3100 multiplexes these requests (combines multip le signals for transmission over a single line) from the numerous client connections into a smaller number of well-regulated, persis tent TCP connections and HTTP requests. This effectively reduces the load on the Web server, freeing up valuable system resources. The 3100 optimizes the management of HTTP connections, handling the chores that servers aren 't very efficient at, such as setting up and tearing down connections.

The 1U rack-mountable 3100 includes three 10/100 Ethernet ports (in, out, and fail-over, if you have multiple NetScalers, which cost $30,000 for a pair). The NetScaler 3200 model (not tested) offers Gigabit Ethernet support.

Performance test results were impressive. The 3100 was able to manage over 340,000 concurrent TCP sessions with a Windows 2000 Web ser ver while averaging between 143 to 202 HTTP gets per second, depending on the back-end server infrastructure.

The 3100 has a 966-MHz Pentium III processor with 512MB RAM, and it runs on a modified FreeBSD 2.4 kernel. Keyboard and monitor ports are located on the back of the unit.

NetScaler includes installation services in the purchase price, though we had little trouble installing the system. Initial installation is completed via a console cable provided in the box. We used HyperTerminal to configure basic settings, such as the IP address. We needed to configure a "mapped" IP address, similar to a virtual IP address, which creates the persistent connections to the servers on the back end.

You can then manage the 3100 in several ways: through the command line, a console, or an adm inistrative Java applet. To use the Java interface, we had to edit a file to include the 3100's IP address and the ma pped IP address. We also had to invoke and run several registration files before launching the applet's GUI. This part of the product needs more development, and NetScaler should compile the applet int o a unified whole.

The 3100's centralized logging feature can be a boon for administrators. It can log activity for multiple servers, significantly easing administration. It also supports SNMP traps, enabling administrators to manage through framework application s such as HP OpenView, Tivoli, or Unicenter.

The 3100 includes a feature known as SureConnect. SureConnect lets sites offer alternative content when Web servers are suddenly overloaded by unexpected traffic, such as that generated by a new product announcement or a news story. Rather than turning potential customers away from the Web site, SureConnect puts visitors in to a queue and estimates the wait time for service. While visitors are waiting, it presents them with discounts or other interesting information , and it automatically returns each visitor to the site once the requested page becomes available. The technology can also tell the difference between Web server delays and those due to appli cation processing.

We tested the 3100's surge protection by launching a barrage of Syn attacks against it. During Syn attacks, Web pages are still served to clients, but at a slower rate. We were finally able to max out the CPU when we launched a barrage of over 100,000 simultane ous Syn, Ping of Death, Land Attack, and Smurf attacks at the unit. Without the 3100, the server's CPU would have maxed out at well below 10,000 attacks.