Drastically Improving WCF Download Times with Gzip + SSL

Header Photo Credit: Lorenzo Cafaro (Creative Commons Zero License)

I put this together last year while looking into ways to improve the amount of time it took to download an approximation 45MB payload SOAP response from a Microsoft Dynamics CRM service (ie: a giant XML document).

In the process, I found surprising results at how much better the user experience was when you combine GZIP compression with SSL encryption.

While the below write-up is specific to CRM in IIS, it should apply much more generally. I hope you find this helpful.

Summary / Real-World Proof

I implemented the below described ssl + gzip IIS configuration to speed up the metadata downloads on an internal server. While I saw no measurable difference in download times from my dev machine on the local network (which downloaded the metadata at approx. 25 seconds), my coworker, who is connecting over a VPN from two timezones away, saw download times go from approx. 5 mins before the change to approx. 30 secs after.

This can be contributed exclusively to the ssl + gzip config change, as we were already running just gzip on the one of our servers and just ssl on another, which were both taking the full amount of time to download metadata. It was only once I enabled gzip and ssl that the times dropped so significantly. Ultimately, this is due to the drastically reduced payload size (data going across the wire) when you combine those two technologies.


After some investigation on how to improve the download times for the CRM metadata, I think on of our best options is to suggest users enable dynamic compression for SOAP data, and utilize SSL. This will significantly reduce the payload size going across the network by ~96%, which represents the overwhelming majority of the user's wait time.


Out-of-the-box, Dynamics CRM will enable the dynamic (GZIP) compression setting for the web interfaces (including WCF services), but IIS7’s default configuration does not consider SOAP to be compressible. You must manually add SOAP to the list of dynamicTypes, which is a host-wide config change. Further, enabling SSL with compression significantly reduces the payload size.

Estimated download payloads and timings:^

  • Default install (IIS7, no dynamic compression, no SSL): 44.5 MB = 8min
  • With GZIP compression for SOAP: 33 MB = 6 mins
  • With SSL only: 33 MB = 6 min
  • With GZIP and SSL: 1.5 MB = 17sec

^Times are best-case, assuming you’re using a network connection with 768Kbps (.09MBps) download speed, the average DSL speed in America. Actual times will likely be slower.

That’s not a typo – enabling both SSL and GZIP took the time down to 17 seconds, or ~3.5% of the original time.

How To:

Step 1: Enable dynamic compress for soap data in the IIS applicationHost.conf

Enable compression by manually updating the ApplicationHost.Config

  • On the CRM Server Navigate to: C:\\Windows\\System32\\Inetsrv\\Config\\applicationHost.config and open it with notepad.
  • Search for the Section: <dynamicTypes> and in that section you should fine an entry that looks like this: <add mimeType="application/x-javascript" enabled="true" />
  • Below that, add the following line: <add mimeType="application/soap+xml; charset=utf-8" enabled="true" />
  • Save the file and reset IIS for the setting to take effect.

Step 2: Ensure dynamic compression is enabled for the Dynamics service:

Note: This should already be enabled in the default configs, but may have been changed by sysadmin

In IIS Manager, open the compression settings for the host:

Ensure dynamic compression is checked.

Open the Dynamics site compression settings:

Ensure dynamic compression is enabled:

Step 3: Enable SSL using a self-signed cert

Follow these instructions to enabled SSL with a self-signed cert.

Step 4: Export the cert and install on desktop

The CRM SDK won't connect to a site with certificate errors, so if using an untrusted (self-signed) cert, you'll need to add it to the desktop's trusted certs.

In IIS Manager, from the Server Certifications page, click Export, select a location to save the file and enter a password.

Copy that file to your desktop machine and double-click the file, which should open the certificate import wizard.

Select Current User (or, to make the cert apply to all users on the machine, select Local Machine) and complete the wizard, using the same password when prompted as you entered on the server during export.

When prompted for which certificate store to use, select "Place all certificates in the following store" and browse to the "Trusted Root Certificate Authorities". Finish the wizard and agree to all of the security warnings (there may be several).

You may need to restart your desktop machine for the certificate settings to take affect.