ACElerate on Fast Track for Load-Balancing
March 8, 1999
By Gregory Yerxa
Until recently, expanding an Internet presence was an arduous task that meant implementing additional, regional Web sites. Now, load-balancing vendors offer more intelligent software that effectively serves Web content from your sites both locally and globally. Load-balancers also increase site reliability and efficiency. Alteon Networks has strengthened its line of load-balancing switches with ACElerate 5.0 switch software and a Global Server Load-Balancing (GSLB) option.
ACElerate 5.0 offers protocol support for server health monitoring, including an API for unsupported protocols. The GSLB capability balances your Web load between all geographically dispersed sites. These features strengthen an already robust feature set that includes support for VLANs (virtual LANs), QoS (Quality of Service), SNMP management and gigabit switching.
In our University of Wisconsin Real-World Labs®, I tested an ACElerate 5.0-driven ACEDirector 2 switch. Alteon's ACEVision Web interface had our test Web site running within five minutes.
Health Check Alteon switches, as well as other load-balancing switches, have monitored server health via network pings or HTTP responses. While effective for the majority of Web sites, these techniques do not monitor other commonly used protocols. Alteon switches configured with ACElerate 5.0 can now monitor HTTP, FTP, NNTP, SMTP, POP3 and DNS servers specifically using each protocol's conventions. ACElerate 5.0 further distinguishes itself with an API that lets you create your own health monitors for nonstandard protocols.
I set up three servers in the lab with SMTP and HTTP services. Next, I configured the ACEDirector 2 switch to load-balance both services across these servers and began generating SMTP and HTTP content. To test the switch's ability to monitor application health, I manually shut down the SMTP service on one of the servers. Unfortunately, this led the ACEDirector to think all services were down, and it immediately stopped sending SMTP and HTTP traffic. According to Alteon, the ACEDirector must disable the entire server, along with all services, when any single monitored service fails. The vendor says that the next version of ACElerate will not have this limitation.
Global Gusto ACElerate 5.0's GSLB component is a global load-balancing agent that redirects client traffic to the most capable site for the fastest response. Although this feature is new to Alteon's offering, other vendors already have products that perform this task. These load-balancers react to network data and server load to handle client traffic in the most efficient way.
ACElerate 5.0 initially directs client requests to the optimal servers via their DNS queries. Since each Alteon switch acts as the authoritative DNS server for the servers and respective server clusters, it doles out the IP addresses of the best servers for each client request. When a site becomes overloaded, subsequent client requests are sent to the most capable site using HTTP redirects. The DSSP (Distributed Site State Protocol) communicates the valid state and statistics to each site and triggers state changes.
To set up the ACESwitch 180 and ACEDirector 2 with GSLB, I configured each switch for single-site server load-balancing via the ACEVision Web interface. Then I configured my local network's DNS server to recognize the local ACESwitch as the authoritative server. With DNS properly configured, I logged in as an administrator to each switch's command-line interface and configured GSLB. First, I configured the switches with IP addresses and then mapped individual virtual server clusters. I repeated this process for both the SMTP and HTTP server clusters I had already configured. Finally, I configured the site's domain name and verified that DNS queries were being served.
Send your comments on this article to Gregory Yerxa at gyerxa@nwc.com.
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