Streaming Media Supplement sa2150 and sa2250

4
Chapter 1 About Streaming Media
Another, proprietary RealNetworks protocol, PNA (Progressive Networks Audio), was replaced by RTSP.
RealNetworks does not use PNA in its current products, although some support PNA to provide backwards
compatibility. A scheme of
pnm
appears in URLs for PNA content, for example:
pnm://audio.npr.org/news.db.rm
Media-IXT supports PNA in a limited way, but the use of PNA should be avoided if possible.
Streaming over HTTP
Streaming over HTTP is normally only a last-resort streaming strategy, chosen by a browser as a fallback after
its preferred strategies fail. Rarely, streaming over HTTP is chosen by a network designer as the primary
streaming strategy for a deployment. If this is true of your deployment, you should be aware of two key points:
• Streaming servers mark streams served through HTTP as non-cacheable, so Media-IXT, being a cache, can
not provide any bandwidth savings or service improvements for such service.
• Streaming over HTTP works by making one persistent connection from the origin server to Media-IXT, and
another from Media-IXT to the client. Media-IXT terminates HTTP connections after a configurable period
of time whose default value is too brief for streaming over HTTP to work properly. The procedure for tuning
Media-IXT’s HTTP timeout values appears in the configuration chapters of this manual.
SMIL files
The SMIL (pronounced “smile”) file is a kind of index file that invokes other files, including both streaming
media files (like movie files) and various types of multimedia files (like JPEG and GIF image files). SMIL
stands for Synchronized Multimedia Integration Language, and SMIL files are text files specifying how and
when the invoked files should play. SMIL files can be hosted by streaming media servers even though the SMIL
file itself is not actual streaming content, but an index to content, some of which may be streaming audio or
video.
Deployment scenarios
Media-IXT is positioned in between the media streaming server and the player, performing proxy caching of
streaming media. That simple statement can be realized in a wide variety of ways, because Media-IXT is a
flexible platform suited to the constantly-evolving nature of internet working.
The table below lists all the possible elements of a Media-IXT deployment. The table shows whether a given
element is discussed in this supplement, in the HP Cache Server Appliance Administrator Guide, or in both.
NOTE The RTP data transfer protocol can use either TCP or UDP as an underlying transport
protocol. Between origin QuickTime servers and itself, Media-IXT uses RTP with TCP
as an underlying transport protocol. On the other hand, current QuickTime players can
only receive streaming data over RTP with UDP as an underlying transport protocol.
Media-IXT deployment element
Where to find a basic description
HP Cache Server Appliance Streaming Media
Administrator Guide Supplement
sa2150 and sa2250
Forward proxy, reverse proxy, and transparency 4 4
Hierarchy 4 8
Live passthrough, live splitting, and hierarchical
live splitting
84
Clustering 4 8
VIP failover 4 4
Selective caching 8 4