SimpleCDN's PPU-MirrorCDN service automatically mirrors and caches your content from any HTTP accessible file store, making your content instantly available via SimpleCDN's Content Delivery Network.

MirrorCDN is not a storage or archival service, rather it acts as a global HTTP Accelerator. Think of MirrorCDN as being similar to Varnish or Squid Cache, except with many more features, and distributed across the world.

MirrorCDN is a pay per use service, with usage billed per GB of data transferred to end users. There are no additional storage or per-request charges.

In order to use the MirrorCDN service, you must first define a Mirror Target. A Mirror Target instructs MirrorCDN where to mirror content from. You use the SimpleCDN Manager to create Mirror Targets.

When a MirrorCDN Edge Cache receives a request for a file, it first checks to see if that file is currently available in its cache. If SimpleCDN's Master Cache has the file, the file will be returned to the Edge Cache, which will then return it to the user. If the Mirror Target actually has the file and returns a 200 OK, the file will be downloaded by the Master Cache, sent to the Edge Cache, and then returned to the user.

MirrorCDN will monitor your Mirror Target a few times per day with HEAD requests, checking for updated content. When updated content is found, it is cached across the global CDN.

Coming Soon: Manual cache updates and an API to request cache updates of certain files.

Content may be removed from Edge Caches and/or Master Caches after a period of download inactivity (a few days). Requests for removed content will still function, since MirrorCDN will re-cache your content from the Mirror Target.

SimpleCDN's distributed architecture maintains a real-time DNS snapshot of the global Internet. This allows SimpleCDN to respond to CNAME DNS requests in near real-time (depending on your DNS server's cache settings).

To create your own CNAME DNS entry for your MirrorCDN Domain, simply follow the instructions below:

MirrorCDN can automatically resize any image, and cache the resized file for instant access.

Function Name: _fn_imageresize

Usage: Use to resize images from your Mirror Target. Resized images are cached for instant access.

Parameters: (image_width,image_height,resize_method)

Example: http://mirror1002.simplecdn.com/_fn_imageresize/750,750,1/250x250.png

MirrorCDN can automatically pull files from any HTTP server by using a specially crafted URL against MirrorCDN. For security, requests must be signed to ensure others do not use your MirrorCDN account for themselves.

Function Name: _fn_anyurl

Usage: Use to have MirrorCDN pull a file from any HTTP server.

Parameters:
URLSafeBase64(target_web_address) / URLSafeBase64(signature) / Optional_NewFileName

Example: Example Link
Constructing URLSafeBase64(target_web_address) in pseudo-grammar:

TargetAddress = "http://images.apple.com/iphone/home/images/hero20080609.png";

TargetAddress_Base64 = ToBase64(TargetAddress);

// Now we have Base64, but we need to make URL Safe.
// Base64 contains "+" and "/" and we need to change those two characters.
// Change "+" to "-"
// Change "/" to "_"

TargetAddress_Base64_URLSafe = Replace(TargetAddress_Base64,"+","-");
TargetAddress_Base64_URLSafe = Replace(TargetAddress_Base64_URLSafe,"/","_");

// Result Should Be... 
// aHR0cDovL2ltYWdlcy5hcHBsZS5jb20vaXBob25lL2hvbWUvaW1hZ2VzL2hlcm8yMDA4MDYwOS5wbmc=

Constructing Signature in pseudo-grammar:

MirrorCDNAnyURLKey = "0123456789abcdefg";

StringToSign = TargetAddress_Base64_URLSafe;

// Now We Sign The String, And Convert the Digest to Base64

Digest = HMAC-SHA1( StringToSign );

Signature_Base64 = ToBase64( Digest );

// Now we Have Signature in Base64, but we need to make URL Safe.
// Base64 contains "+" and "/" and we need to change those two characters.
// Change "+" to "-"
// Change "/" to "_"

Signature_Base64_URLSafe = Replace(Signature_Base64,"+","-");
Signature_Base64_URLSafe = Replace(Signature_Base64_URLSafe,"/","_");

// access key: 0123456789abcdefg
// to sign: aHR0cDovL2ltYWdlcy5hcHBsZS5jb20vaXBob25lL2hvbWUvaW1hZ2VzL2hlcm8yMDA4MDYwOS5wbmc=

// result: UiGN58EH_sIZgR6cHCXx_n0_SUc=

At the end of the URL you may enter any "filename", which will help to ensure the server sends the correct mime-type to the browser. Even though the AnyURL is going and getting a file named hero20080609.png, we have decided to call the image iphone.png. You may enter anything here, it will not affect the AnyURL, just the way the browser handles the file download.

Certain MirrorCDN functions may be stacked together. For example, you may place _fn_imageresize before _fn_anyurl.

Example: Example Link

This example combines the iPhone image example from the AnyURL function, with the Image Resize function, resizing the image to 1200 x 1200 with a grey letterbox.
Notice how the Image Resize function supports transparency in PNGs.

MirrorCDN will NOT honor requests with query strings for static elements, rather query strings will be stripped from requests made against MirrorCDN.

However, requests for .html, .htm, .shtml, .jsp, .cfm, .php, .asp and .aspx files that contain query strings will be transparently proxied to the origin server.
For example, MirrorCDN will treat the following three image requests as equal, and will serve the same file to all three.
This is done to prevent like files from continually being re-cached due to varying query strings, which are very common these days due to web analytic software, etc.

MirrorCDN will NOT cache HTTP POST request responses, and will instead transparently proxy HTTP POST requests to the origin server.

MirrorCDN is billed on a per GB of data transferred model. Charges for transfer are calculated and billed against your SimpleCDN Credit balance throughout the day.

If your account does not have enough credits to pay for current GB usage, your account may be terminated within 72 hours.