Purpose of RadCompression in my asp.net app

I was looking to optimize my Telerik based app, and saw the 'RadCompression' capability. My understanding is that this tool will compress the viewstate, but in my case all .aspx content is already gzipped to the clien开发者_开发百科t. In which case, what additional value does RadCompression give me? Is this tool some remnant from the IE6/golden days, where gzipping content was more of an issue?

The RadCompression about page explains it very well:

Simply put, RadCompression is a HttpModule that ships with the RadControls for ASP.NET AJAX that is designed to automatically compress your AJAX and Web Service responses. In other words, RadCompression will intercept the bits that your server is sending back to a browser (or Silverlight-client, for that matter) and compress them. Once the compressed bits reach the browser, standard browser technology takes-over and decompresses the response, so your application can work with it normally. The compression process is completely transparent to your client-side code (JavaScript or Silverlight) and your server-side code. It simply reduces the number of bits that must be sent over the wire (from your server to your client) and thus- in theory- improves your page performance by reducing the TTLB (time to last byte).

It goes on to explain what it does NOT do:

RadCompression is not designed to be a complete replacement for other HTTP compression tools, such as the built-in HTTP Compression in IIS 7. Instead, it is designed to work with those existing tools to cover scenarios they usually miss - namely the compression of bits moving back and forth in AJAX (and now Silverlight) applications.