IIS7 Web.Config Caching - what are the differences here, and how does it all come together?

Question

In IIS7 I've got the ability to set caching options. These options are added to my web.config as such...

    <caching maxCacheSize="262144">
        <profiles>
            <add extension=".png" policy="CacheUntilChange" kernelCachePolicy="CacheUntilChange" duration="00:00:30" />
            <add extension=".jpeg" policy="CacheUntilChange" kernelCachePolicy="CacheUntilChange" duration="00:00:30" />
            <add extension=".jpg" policy="CacheUntilChange" kernelCachePolicy="CacheUntilChange" duration="00:00:30" />
            <add extension=".css" policy="CacheUntilChange" kernelCachePolicy="CacheUntilChange" duration="00:00:30" />
            <add extension=".js" policy="CacheUntilChange" kernelCachePolicy="CacheUntilChange" duration="00:00:30" />
        </profiles>
    </caching>

However, I've also got the following for "caching"

    <staticContent>
        <clientCache cacheControlMode="UseMaxAge" cacheControlMaxAge="90.00:00:00" />
        <remove fileExtension=".js" />
        <mimeMap fileExtension=".js" mimeType="text/javascript" />
    </staticContent>

What are the differences between these two configs? They are both nested in the <system.webServer> tag, so they're both valid for IIS7.

Also, what is the right approach when using these? I currently only use this is my static assets folder. I don't use this caching on anything else.

Thanks in advance.

Answer 1

The main difference is that

• the first is for server-side caching of dynamic output such as aspx pages (basically keeps the page output in memory for subsequent requests). As @artem-vertiy's answer points out, using it for static content makes no sense.

• the second one is 'internet-side' : it is implemented by writing standard response headers, it tells both client browsers and public proxies how to manage cached files.