We recently switched to Amazon Cloudfront for static content. It seems that Cloudfront does HTTP 1.0 requests to the origin server (IIS 7.0) using the Via header. By default IIS 7.0 disables file compression for both these options (HTTP 1.0 and proxy (Via) requests), which can only be enabled for the entire server by setting the noCompressionForHttp10 and noCompressionForProxies to false in the applicationHost.config (http://msdn.microsoft.com/en-us/library/ms690689(v=vs.90).aspx).

My question is: what is the risk of enabling compression for HTTP 1.0 and proxy requests? Are these settings meanth for REALLY old browsers/proxies (eg. Internet Explorer 5) or does the problem exist in more recent browsers/proxies?


It should be safe to set those options.

Looking at the default Apache 2.2 conf in Ubuntu 12.04 (/etc/apache2/mods-available/deflate.conf), it looks like IE 6 had some problems with compression for CSS, RSS and Javascript.

Also, some really old proxies don't support the 'Vary' header, and would thus send cached, compressed contents to clients who did not indicate compression support in their 'Accept' header.

If your webserver ONLY gets accessed through the CDN, then those two options don't matter at all. If you still allow direct access to your webserver, then, as you said, really old browsers/proxies might have a problem (but users of such ancient products will face a host of other problems...)

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