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Q. I want to use Windows NT/2000 Load Balancing Service for multiple webservers in a cluster. What do I need to consider when using WLBS and/or Microsoft Application Center (MAS) with AuthentiX/WebQuota?


You will need to authenticate against a centralized ODBC database.

Basic Authentication will work just fine if a user is switched from one machine to another.
Cookie-based should work fine too (the AuthentiX Cookie based protection is not session based, so there are no worries about storing sessions in a back end db). However you will not be able to utilize the AuthentiX server-side cookie timeout feature (setting a cookie to expire on the browser will still work of course).

Unlike session based systems (see the white paper on affinity below) AuthentiX works great on clusters. If you have any problems, please let us know.

In the white paper for Microsoft Windows NT/2000 Load Balancing Service, the section on Affinity and Session Support provides the key information:
"WLBS supports client sessions and Secure Sockets Layer (SSL). If a server application (such as a Web server) maintains state information about a client session that spans multiple TCP connections, it is important that all TCP connections for this client be directed to the same cluster host. Should a server or network failure occur during a "stateful" client session, a new logon may be required to re-authenticate the client and re-establish session state."

So long as the domain name (eg remains the same across requests, then the browser will continue to supply the cookie-based or Basic Authentication logon credentials in the http request. If you have AuthentiX installed on each machine in the cluster, then users will not have to login each time they are served by a different machine in the cluster.

The white paper goes on to say:

WLBS also allows modification of session support to direct all client requests from a TCP/IP Class C address range to a single cluster host. This feature ensures that clients which use multiple proxy servers to access the cluster will have their TCP connections directed to the same cluster host. The use of multiple proxy servers at the client's site causes requests from a single client to appear to originate from different systems. Assuming that all of the client's proxy servers are located within the same 256 host Class C address range, WLBS ensures that client sessions are properly handled with minimum impact on load distribution among the cluster hosts."

WebQuota and WLBS both use this same method of dealing with proxy clients such as AOL.

Another opinion on load balancing from Adwait Ullal:
"Your best (and easiest, in terms of no coding changes) bet would be to look at any of the hardware load balancers, such as Cisco's Local Director, Alteon (I forget the product name), etc.
They usually have a 'sticky bit' option wherein a user coming to a particular server will return to the same server on subsequent visits."

More info from Hank:
I successfully clustered the Authentix by installing the application on node A while it has control of the drive array that is swapped between nodes. Once finished, swap nodes and install the application on node B (GUI and ALL).

Anytime you move nodes, your GUI will work. Here is the catch to making this work. Copy the flicksflt (sorry am at home and don't remember the exact name of the filter for IIS) DLL and the OCX to a location on your C: or OS drive. You will have to go to IIS MMC and point to the filter that you copied to the C: or OS drive. Do this on each node.

The reason why I had to do this is that whenever the nodes were moved, the web sites would fail and try to roll back to the node that initiated the move. I think the reason why this happens is that IIS is not ready because of the filter DLL and OCX are trying to be started from that shared drive array. If you move them to the C: or OS drive, IIS is happy because it always has a copy of the IIS filter.

Hope this helps.


Also see here .

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