The Client in this case was a large European banking institution.  A project was underway to port an existing in-house account-management application to the Web.  In addition to sophisticated application design requirements, such as high security, fast response time and cross-browser independence, there were also numerous system design requirements, including primarily:

	Compatibility
	Scalability
	Load Balancing
	Equipment Failover & Redundancy

It is immediately clear from these requirements that clustering technology must be employed -- for which there are currently several solutions, via both hardware and software.  Prior to Quest's involvement in the project, it had already been decided to use Microsoft software, to provide maximum compatibility with the existing Windows NT-based infrastructure.  This included Microsoft Site-Server Commerce Edition and Microsoft SQL Server, the latter in  a highly cutting-edge Active-Active Vitual configuration.  This construction satisfied the Compatibility requirement, and also supported back-end load-balancing and failover. 

It was further determined that a combination of Microsoft's Windows Load Balancing Service (WLBS) and Microsoft Cluster Server (MSCS) would be employed, to provide Scalability and Load Balancing for the front-end webservers, plus Failover & Redundancy for the back-end database servers.  With this general project plan, it was then Quest's task to build the proof-of-concept systems.

Before even arriving at the client site, Quest built a custom CD with all necessary software patches and service packs germane to the project.  We also began verifying software compatibility in one of our test labs, especially since we knew from experience that the installation of Site Server Commerce Edition and MSCS were both especially delicate, requiring that one follow an extremely precise installation procedure.  We immediately realised several project design flaws, most importantly:
 

	Networking Incompatibility.  The client's site was 100% Token Ring, and WLBS requires Ethernet to function.  This required the last-minute configuration of a Token Ring-to-Ethernet router, to provide access to the Ethernet proof-of-concept systems (for which Ethernet NICs and an Ethernet hub were quickly ordered).
	Software Incompatibility. The original intention was to install MSCS on the second-tier application servers.  This is ordinarily a good idea, however, these servers were also to be used as LDAP servers...and Microsoft Site Server is not cluster-aware!  We offered the client two solutions: either move the LDAP services other systems, or change the second tier to WLBS.

After correcting these design flaws, we then proceeded with the installation and configuration.  The first two WLBS tiers installed perfectly.  MSCS installed perfectly.  The Virtual SQL Server installation, however...failed!   We were perplexed, since it had worked perfectly in our test labs, with similar equipment.  This pointed to one of two possibilities: either the client's equipment was somehow incompatible with the software (which we ruled out after a quick SQL Server Hardware Compatibility List double-check), or there was something peculiar to the client's network that was causing the failure. 

The answer was not obvious, and turned out to be a combination of problems.  The first one we found almost immediately:  one of the servers had been entered incorrectly in DNS, causing a name resolution failure.  But this alone could not explain all of the failure.  So we began by doing a quick network audit -- topology, protocols, service pack levels -- and shortly found our answer in the system global hardware policy:  NetBIOS over TCP/IP was being disabled at login!   We knew that the Virtual SQL Server installation process includes a domain login. . . and requires NetBIOS over TCP/IP to complete and function.  Case solved, with one small registry entry. 

* * *

The results?  By the end of the week had a perfectly-functioning
e-commerce site, including a WLBS-enabled webfarm with an Active-Active Virtual SQL Server database cluster. And we might also mention that we had a very, very happy client.