Another possibility is the client is not sending the session cookie. I would 
check the cookie domain on the client, if each server in your farm issues a 
cookie with a host specific domain that would explain the behavior you are 
seeing.  You might need to set a common cookie domain in the web.config.



On Apr 23, 2011, at 10:44 AM, "Ryan Riley" <[email protected]> wrote:

> Firstly, sorry about misspelling your name. I was still half asleep, but 
> that’s no excuse. My bad.
> 
>  
> 
> We aren’t getting switched up sessions. It’s more like user A hits server 1, 
> then bounces to server 2, but server 2 doesn’t know how to retrieve the 
> session for user A correctly.
> 
>  
> 
> Thanks for the link and info on patch levels. I haven’t checked into that 
> yet, so I will.
> 
>  
> 
> Regards,
> 
>  
> 
> Ryan Riley
> 
>  
> 
> From: [email protected] [mailto:[email protected]] 
> On Behalf Of Shawn Neal
> Sent: Saturday, April 23, 2011 8:33 AM
> To: [email protected]
> Subject: Re: Network Load Balance Testing
> 
>  
> 
> What do you mean by, "wrong session information?"  Does that mean user A 
> sometimes gets the session data for user B, or user A has 2 unique sessions?
> 
>  
> 
> Session state is only dependent upon the session cookie and not source IPs.  
> One issue you can have in a web farm is if they have different .NET patch 
> levels, specifically this hotfix: http://support.microsoft.com/kb/2416472.  
> It changes how .NET decrypts view state and session cookies amongst other 
> things.  If you have two servers in a farm, one with and one without the 
> patch, you'll have all kinds of problems... even if they have the same 
> machine keys.
> 
>  
> 
> On Sat, Apr 23, 2011 at 8:05 AM, Ryan Riley <[email protected]> 
> wrote:
> 
> Thanks for your response, Sean.
> 
>  
> 
> We are using Microsoft NLB, and we have a few scenarios where reverse proxies 
> cause our customers HTTP and HTTPS traffic to come from different IP 
> addresses. We are using SQL Server Session storage on a shared database 
> server, and our machine keys are the same on both of our NLB web servers. 
> However, we’ve watched what appear to be valid requests not pull in the 
> correct session information when the user session hops between our servers.
> 
>  
> 
> I’m trying to figure out how I can reproduce this locally so that I can 
> isolate and resolve the problem in our web app, NLB cluster, or whatever else 
> is actually causing the problem.
> 
>  
> 
> Thanks!
> 
>  
> 
> Ryan
> 
>  
> 
> From: [email protected] [mailto:[email protected]] 
> On Behalf Of Shawn Neal
> Sent: Friday, April 22, 2011 6:34 PM
> To: [email protected]
> Subject: Re: Network Load Balance Testing
> 
>  
> 
> Are you trying to determine the overhead of having to renegotiate SSL when 
> switching between https and http and/or between https requests?  Are you 
> specifically talking about Windows NLB?
> 
>  
> 
> There's definitely overhead if you have to renegotiate a SSL session between 
> each request if the load balancer sends you to a different server every time. 
>  I'm not sure how/if Windows NLB handles this.
> 
>  
> 
> When we were testing SSL re-negotiate overhead we ended up doing this in our 
> performance lab with Load Runner.  We basically compared ART and CPU of load 
> balanced http, https, and https with sticky sessions (didn't try SSL term at 
> the VIP).  We ended up using SSL with sticky sessions because we were able to 
> use commodity hardware using layer 4 routing via HA-Proxy rather than dealing 
> with the overhead of layer 7 or an expensive hardware load balancer.
> 
>  
> 
> Good luck!
> 
>  
> 
> -Shawn
> 
>  
> 
> On Fri, Apr 22, 2011 at 4:43 PM, Ryan Riley <[email protected]> 
> wrote:
> 
> Any recommendations on testing a NLB environment? In particular, I'm trying 
> to find a way to explore the impact in our environment of bouncing between 
> our NLB servers, especially when switching between HTTP and HTTPS. Any 
> thoughts are appreciated. I'm having a hard time tracking anything down on 
> this one.
> 
>  
> 
> Cheers!
> 
> 
> Ryan Riley
> 
> Email: [email protected]
> LinkedIn: http://www.linkedin.com/in/ryanriley
> Blog: http://wizardsofsmart.net/
> Website: http://panesofglass.org/
> 
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