Slow Connectivity for Outlook Anywhere and Sites that use the SBS Web Applications App Pool

[Today's post comes to us courtesy of Wayne McIntyre, Justin Crosby, and Damian Leibaschoff]

We have discovered an issue where connections to Outlook Anywhere are extremely slow or fail completely. Another behavior is that when you try to connect to HTTPS://REMOTE.CONTOSO.COM it just sits in a waiting state, while trying HTTPS://REMOTE.CONTOSO.COM/REMOTE or HTTPS://REMOTE.CONTOSO.COM/OWA works fine. This issue affects all sites that use the SBS Web Applications app pool. The reason this happens is due to the default setting of 2.0’s default maximum concurrent requests of 12 per CPU. When using RPCProxy which is used by both Outlook Anywhere and TS Gateway, the connections are asynchronous which can cause you to hit the limit of 12 pretty fast. For more detail on thread usage and this limit please read.

If you notice these symptoms and wish to verify you are experiencing this problem, open IIS management console and check the worker process queue for the SBS Web Applications app pool as shown below.

1. Select your Server name in the tree view and double click on Worker Processes.


2. Double click on the SBS Web Applications application pool


3. You will notice a number of BeginRequest for the HttptoHttpsRedir module with a high amount of time elapsed.


New Resolution

  1. Open regedit with administrative permissions.

  2. Create the below DWORD and set its value to 5000 decimal to increase the limit of concurrent requests.

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ASP.NET\2.0.50727.0\ MaxConcurrentRequestsPerCPU

Original Resolution (from 1/28/2009)

We are including the old resolution for reference. If you are encountering this error or have implemented the original fix, please implement the new resolution as seen above. There is no need to undo the original fix. The two fixes can exist side-by-side.

To resolve this issue we suggest that you remove the HttptoHttpsRedir module from the /RPC virtual directory only.

1. From IIS Manager -> Expand Sites -> Expand SBS Web Applications -> and click on the RPC vdir -> double click on the Modules Icon in the feature pane.


2. From within modules, select the HttptoHttpsRedir module and click on Remove in the actions pane.


Updated 2/10/2009: Included new resolution.  If you already implemented the original resolution we recommend that you also implement the new resolution.  There is no need undo the previous fix.