HostMonitor Causing Bad Behavior with Windows NLB

aneveu · Post by **aneveu** » Tue Jul 24, 2012 7:32 am

Hello,

Please have a look at this Forum post that describes some undesirable behavior that HostMonitor seems to cause to Microsoft's Network Load Balancing:

http://social.technet.microsoft.com/For ... 7755f33385

The summary is that when using a URL Request test method it looks like HostMonitor does the following strange things:

1) Before making the HTTP GET request, the scale factor is negotiated every time.

2) The complete HTTP response is not retrieved using continuation packets, but only the first 200 OK response is retrieved.

Any comments on this?

KS-Soft · Post by **KS-Soft** » Tue Jul 24, 2012 8:36 am

2) The complete HTTP response is not retrieved using continuation packets, but only the first 200 OK response is retrieved.

Its depends on test settings. You may tell HostMonitor to check web page so it will retrieve complete page, also you may tell HostMonitor to retrieve images and nested frames. If you use none of these options, then yes, HostMonitor will retrieve HTTP header only.
Its up to you...

1) Before making the HTTP GET request, the scale factor is negotiated every time

There are 2 test methods: HTTP test and URL test.
HTTP test method uses our own code so I can tell you what exactly HTTP requests can be sent by HostMonitor.
URL test method uses Microsoft WinInet and WinHTTP API. We do not have 100% control over this code but it should work pretty similar to IE that uses the same API.
HostMonitor does not use any special requests related to NLB "scale factor". Truth to say I am not sure this is possible using WinInet API. May be depends on some new IE settings...

Regards
Alex

aneveu · Post by **aneveu** » Tue Jul 24, 2012 8:42 am

Great info, so how do I configure HostMonitor to retrieve the complete page? I am using the URL test method. I do not want it to retrieve all the associated images, just the complete page itself rather than the header only. If I can get this much done, it will help diagnose the problem to a large degree I believe, and perhaps I won't have to worry about the "scale factor negotiation" thing.

Ahh, I just tried "Download nested frames" and that seems to do it. I'll reply back later if this solves the whole problem!

KS-Soft Europe · Post by **KS-Soft Europe** » Tue Jul 24, 2012 8:51 am

You may enable "Check contents" option. In such case HostMonitor will retrieve HTTP page.
Also, you may use %HttpPage% macro variable with actions. It contains retrieved HTTP data.

Please check the manual or visit our web site for more information at:
URL request test: http://www.ks-soft.net/hostmon.eng/mfra ... ts.htm#url
%HttpPage% macro variable: http://www.ks-soft.net/hostmon.eng/mfra ... ificmacros

KS-Soft · Post by **KS-Soft** » Tue Jul 24, 2012 9:00 am

Great info, so how do I configure HostMonitor to retrieve the complete page? I am using the URL test method. I do not want it to retrieve all the associated images, just the complete page itself rather than the header only

Then just use either "Check contents" or "Check CRC" option.

Ahh, I just tried "Download nested frames" and that seems to do it. I'll reply back later if this solves the whole problem!

Well, this option was designed for different reason, however if you just need to retrieve single page, it can be used as well.

Regards
Alex

aneveu · Post by **aneveu** » Tue Jul 24, 2012 9:00 am

I checked the "Download Nested Frames" checkbox and that makes HostMonitor request all the continuation packets, just like IE9. This winds up with repeated success and does NOT cause NLB to do the bad behavior of the Connection Down action. So I have updated my post on the Microsoft TechNet Forum stating as much, and now I will wait to hear back from that forum to see if anyone can tell me why NLB does this, if it is by design, etc. The summary statement at present goes like this:

NLB performs the Connection Down action in response to multiple requests for a page when the client only retrieves the HTTP Header and no further TCP continuation packets are requested.

I am waiting for someone to confirm, deny, or qualify that statement. But HostMonitor has been absolved of any responsibility in this matter, so nice job in responding to this inquiry with helpful info. We love our HostMonitor!

Have a great day!

KS-Soft · Post by **KS-Soft** » Tue Jul 24, 2012 9:01 am

Thank you