Streaming Media Supplement sa2150 and sa2250

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Chapter 2 Media-IXT Deployment Scenarios
Simultaneous forward and reverse proxy caching
Media-IXT can perform forward proxy and reverse proxy simultaneously, and does so by default when
configured for reverse proxy caching.
Here is an example of where simultaneous forward and reverse proxy caching would be useful. There are many
other possibilities, and this example is not intended to suggest that this is the only plausible scenario.
• Access Provider X has a business alliance with Content Provider Y.
• Access Provider X has clients who use Media-IXTs owned by Access Provider X as a forward proxy for
requests going out to the Internet.
• Access Provider X also configures its Media-IXTs to perform reverse proxy caching for the origin servers
of Content Provider Y.
The result is that Access Provider X’s customers enjoy optimal performance from Content Provider Y’s
websites, as well as the benefits of having a forward proxy cache when they request content from elsewhere.
Figure 2-4, below, shows such a deployment in a simplified way.
Understanding hierarchy
You can deploy a hierarchy of Traffic Servers to perform hierarchical proxy caching, in which child caches
redirect traffic to parent caches in the hierarchy.
Hierarchical deployment of Media-IXT may be transparent or explicit; we document the explicit form in this
manual. You put explicit hierarchy into effect by enabling parent caching, then writing rules in the
parent.config file. For transparent hierarchy, you use various means other than these. Transparent
hierarchy is complex and should be approached with caution.
See the HP Cache Server Appliance Administrator Guide for an explanation of hierarchical proxy caching, and
for details about editing parent.config. Keep in mind that the HP Cache Server Appliance Administrator
Guide only describes hierarchical caching for HTTP traffic. For Media-IXT, of course, you must also consider
RTSP and MMS traffic.
Traffic Manager allows you to enable parent caching, and designate a parent cache. Although the GUI does not
make this clear, this affects HTTP only. All configuration of hierarchical caching for RTSP or MMS must be
done by editing parent.config.
Each rule in parent.config applies to one protocol only. Where one protocol is used by two streaming
formats, you can add tags to a rule to designate to which of those streaming formats it applies. This means that
one child cache can have different parents for different protocols. It also means that even if a child has the same
parent for all protocols, you must write a separate rule for each protocol used in the hierarchy.
Figure 2-4. Simultaneous forward and reverse proxy caching
Access Provider X’s
Web Clients
Access Provider X’s Network
L4 Switch
Access
Provider X’s
Media-IXT
Reverse Proxy
Forward Proxy
KEY
Content Provider Y’s
Origin Server
To Other
Origin
Servers
World Wide Web