Streaming Media Supplement sa2150 and sa2250

Chapter 4 Understanding Media-IXT and WMT

Understanding reverse proxy caching for WMT

In a sense, reverse proxy caching is simpler than forward proxy caching for WMT. The

map

and

reverse_map rules used in reverse proxy save Media-IXT some URL-rewriting work, as you will see.

Like forward proxy caching, reverse proxy caching of WMT content can be based on these three nodes:

• a Windows Media server, where content resides in the form of files in WMT streaming formats:

.asf,

.wma or .wmv files

• a web (

HTTP

) server, where .html files reside that contain hyperlinks to the WMT metafiles (.asx,

.wax or .wvx files); the WMT metafiles, in turn, contain pointers to the WMT content files

• the Media-IXT host

You must configure the nodes so that:

• the Media-IXT node answers to the advertised name of your Windows Media streaming content website–

precisely what the HTTP server would do if your Media-IXT did not exist

• the remap.config file on the Media-IXT host contains the appropriate map and reverse_map rules

• the proxy.config.reverse_proxy.enabled variable in Media-IXT’s records.config file

is set to true

For details about how Media-IXT can perform reverse proxy exclusively, or forward proxy exclusively, or both

together, see “Simultaneous forward and reverse proxy caching for WMT” on page 44.

For details about writing remapping rules and other aspects of configuration see “Configuring reverse proxy

caching for WMT” on page 85.

To show how reverse proxy caching works for WMT step by step, we consider an example in which a user has

a web browser with Windows Media Player, and is viewing the home page of the website, www.pix.com

Media-IXT is serving that home page because Media-IXT has been configured to answer to the advertised

server name, www.pix.com

The action begins when the user clicks on a link for a movie called Funnymovie.

1. The browser sends a request for the WMT metafile:

http://www.pix.com/funnymovie.asx

2. Media-IXT locates the WMT metafile on the HTTP server using the map rule:

map http://www.pix.com/ http://relay.pix.com/

The WMT metafile funnymovie.asx contains a pointer to a streaming file on a Windows Media origin

server:

mms://source.pix.com/funnymovie.asf

3. Media-IXT rewrites the streaming file's URL using this reverse_map rule:

reverse_map mms://source.pix.com:1755/ mms://www.pix.com:1755/

The rewritten URL invokes Media-IXT rather than the origin Windows Media server:

mms://www.pix.com/funnymovie.asf

4. The rewritten URL is simpler than the kind we use for forward proxy caching of WMT content, because it

does not contain the name of the Windows Media origin server; it does not need to, since our map rules find

the origin server for us.

5. Media-IXT forwards the rewritten WMT metafile to the browser.

NOTE The Windows Media server and the web server can be on the same node.