Stream Caching with TeraEDGE - continued

Caching on-demand content
Like a web cache, a media cache records content supplied by origin servers in response to user requests. When the same user, or a different user, requests the same content, it is fetched from the cache instead of the origin server. When delivering cached content, response is faster, quality is higher, and upstream bandwidth consumption and costs are reduced. Like their web counterpart, media caches must verify content freshness and may operate in transparent or non-transparent mode.

But the content stored by a media cache must be treated as a borrowed asset, made available for resale. The media cache must proxy licensing schemes, authentication, accounting and usage statistics by establishing an RTSP control session to the origin server whenever a client requests previously-cached content. The cache should protect against unauthorized access to stored content. For example, the Real Networks RealProxy 2.0 encrypts content replicated locally, and terminates client streams if the server becomes unreachable during replay.

Media caches can also leverage their role to overcome quality problems that plague live streams. According to Entera's Dave Immethun, "With our RTSP/RTP agent, we respect all the same billing, authentication, concurrent licensing schemes, and error checking as the Real Proxy." But Entera didn't stop there. "Our patented technologies are some of the ways we ensure origin-quality content is stored in the TeraEDGE, even over congested networks."

TeraEDGE features
What makes the TeraEDGE unique? "TeraEDGE works in conjunction with TeraCAST to receive and combine multiple concurrent streams," said DeSoto. "If you don't do this, you'll lose packets and quality will suffer. We combine—or seam— multiple streams to produce 99.9% error-free images."

TeraEDGE supports multiple transfer agents, enabling concurrent caching of content delivered over HTTP/FTP, RTSP/RTP, and RTSP/RDT today. "Our [RTSP/RTP] Transfer Agent can also copy partial or full files from the origin server," said DeSoto. If packets are lost during the original capture session, Entera's Transfer Agent sends follow-up requests to the origin server to retrieve the missing packets and store them, at the indexed location, in the cached file.

Then there's smoothing. "We buffer out streams, not only from the server, but heading to the client, for consistent signal," said DeSoto. This is important for streaming through media players like QuickTime that don't have their own internal buffer.

To improve the quality of live sessions, Entera implements Dynamic Reflection, a technique whereby TeraEDGE connects to the TeraCAST server that is physically closest to the user. By shortening the delivery path, quality and resource consumption are optimized.

These features are patent-pending, but Immethun said that Entera's packet recording solution was presented to the IETF "so that we could improve the quality of content stored from non-TeraCAST RTSP/RTP servers." In fact, Entera hosted an RTSP Interoperability Event in late July. "We brought together 27 attendees from competitors like Real Networks, Cisco, Sun, and Microsoft," said DeSoto. "Our goal was to demonstrate interoperability of clients using RTSP protocols, not for publication but for presentation to the IETF. Anything that facilitates content delivery is good for us and good for the market. And our customers are asking for streaming protocols to be standardized."

Initial deployment by Axient will stream summer Olympics
Although it's been in beta since March, Entera officially launched TeraEDGE in August, at the same time they announced their first customer, Axient Communications. According to DeSoto, "Axient will be broadcasting the Olympics to the US market on a time-delayed basis, using our products as a platform: TeraCAST as an origin server, and TeraEDGE as a content delivery server. Axient will roll out our products in about 65 locations for this event, and probably about 200 locations by year end."

"In Axient's case, we're providing both origin and distribution servers, and content will be delivered to QuickTime clients," said DeSoto. "For the Olympics, you want to be really sure everything will work, and when you're mixing proprietary and non-proprietary solutions, anything can happen." Axient will actually be "broadcasting" the Olympics over a high-performance overlay network called Octane, pulling content from TeraCAST servers in Sydney, Australia and distributing it, through TeraEDGE, to ISP partners across the US.

Axient's ability to "restrict the territorial footprint of streaming media to the US marketplace" was a deal-maker, according to Tom Newell, general manager of NBC/Quokka Ventures. The International Olympic Committee (IOC) ruled out unlimited Internet streaming because it conflicted with country-by-country TV broadcast deals made by the IOC. But NBC holds exclusive Olympic broadcast rights in the US and will be permitted to stream Olympic video clips in this controlled fashion, over Axient's Octane network.

page 3: Under the hood