Streaming Media Supplement sa2150 and sa2250

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Chapter 4 Understanding Media-IXT and WMT
In rewriting the URL, Media-IXT places the prefix ink/rh before the HTTP server hostname.
• ink/ serves as an indicator to Media-IXT that the URL has been rewritten. This is important in hierarchical
deployments.
• rh stands for HTTP Redirector Host.
Understanding forward, transparent proxy caching for WMT
For an explanation of transparency devices (layer 4 switches and WCCP2 routers) see Chapter 2‚ Media-IXT
Deployment Scenarios.
This section describes a deployment scenario based on HTTP transparency and WMT metafile rewriting. Other
possibilities are discussed at the end of the section.
Media-IXT uses HTTP transparency, provided by a layer 4 switch or WCCP2 router, to intercept a browser's
request for the WMT metafile. Then Media-IXT rewrites the WMT metafile so that Windows Media Player
directs its requests for streaming content to Media-IXT.
You can configure your layer 4 switch or WCCP2 router to provide transparency for MMS as well as HTTP.
(In fact, you can choose either one, or both kinds of transparency.) MMS transparency allows a WMT client to
obtain streaming content directly from the origin Windows Media server, in the event that Media-IXT becomes
unavailable. So MMS transparency makes your deployment more robust, and is usually a good thing to have.
How Media-IXT handles HTTP transparency for WMT streaming
Our example assumes that the user of a web browser equipped with Windows Media Player is viewing an
HTML page containing links to movies. The story begins when the user clicks on a link to a movie.
1. The browser sends out an HTTP request addressed to port 80 of a Windows Media origin server.
2. A layer 4 switch or WCCP2 router, detecting a port 80 request, intercepts the request and redirects it to
Media-IXT.
3. Media-IXT rewrites the contents of the WMT metafile.
4. Media-IXT serves the metafile to the browser. The rewritten metafile directs Windows Media Player to
obtain streaming media content from Media-IXT.
5. The browser passes the WMT metafile to Windows Media Player.
6. Windows Media Player contacts Media-IXT (not the origin server) for the streaming content.
7. Media-IXT obtains metadata about the media content invoked by the URL from the origin Windows Media
server. ts4
8. Media-IXT tries to find a match between the origin Windows Media server's metadata and metadata in
Media-IXT's cache. If Media-IXT finds an exact match, then the content is in cache and fresh. If not, Media-
IXT obtains the content from the origin server, and caches it as it servers it to the Windows Media Player.
9. Media-IXT streams the content from cache.
The figures below illustrate an instance of Media-IXT performing proxy caching of WMT content, with a layer
4 switch providing transparency.