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Multicast: Keeping the Stream Flowing



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August 2001

December 14, 1999: Three million people flock to a Webcast of Paul McCartney live at the fabled Cavern Club where the Beatles began. Inside the club, the concert is electric, as McCartney and band members rock out to "I Saw Her Standing There," "All Shook Up" and lots more. Not so for Web viewers. Thousands can't access the concert at all. For those who brave crushing Web traffic to log on, the event is marred by interruptions in the feed, fuzzy images and muddy sound.

It's been 19 months since the McCartney Webcast -- ages in Internet time -- but online broadcasts are just as problematic. More recent Webcasts such as a Madonna concert and the U.S. NCAA Final Four playoffs have been plagued by similar access and quality problems.

That could change, thanks to a tool developed by researchers at HP Labs that helps manage the delivery of streaming media to large audiences. Now an HP product called OpenView Network Node Multicast, the software uses a graphical user interface that makes it easier to see and manage media streams, while reducing network congestion and the number of servers required.

Unlike most current streaming media offerings, which support unicast technology, the HP tool helps enable multicast over Internet protocol. In unicast, separate streams are sent each time an individual user clicks on a link requesting the streaming media content. By contrast, multicast allows transmission from each media server to many people simultaneously.

Too many people = too much of a good thing

To plan for large audiences, Internet service providers typically over-engineer their sites and networks, configuring a large number of media servers and huge amounts of network bandwidth to meet sudden spikes in demand. Too much demand means trouble: Servers get overtaxed and streams falter or fail.

Researchers Ed Perry and Puneet Sharma tackled the problem by examining the weaknesses of unicast technology. For live or simultaneously broadcast events, unicast uses too much network bandwidth and too many media servers. That's because the media servers must process individual requests for streaming media content from tens, hundreds or thousands of users and then send duplicated media streams.

Quote: 'This product brings news ways to manage and use streaming media within corporations.' says Perry.'

By contrast, multicast places less pressure on media servers and on networks because it minimizes the resources required to deliver simultaneous media streams. Only one server may be required and there are no duplicated streams of data. That puts less pressure on the network. Multicast capability is built into network routers made by companies such as Cisco Systems and Juniper Networks.

No multicast management tool, no multicast

Despite this, organizations weren't using multicast because, without adequate tools to manage it, they found diagnosing multicast faults to be terribly time-consuming and to require great expertise. They were unable to see how multicast was affecting their networks, their media-server infrastructure or the recipients of the streaming media content.

The attitude was, "No multicast management tool, no multicast," recalls Perry.

So Perry, Sharma and their team at HP Labs set out to develop a multicast management tool. They spent two years writing the software code and testing prototypes with enthusiastic customers.

"One challenge," says Perry, "was to develop an interface that would allow people to see and troubleshoot network problems."

Seeing problems as they arise

Perry's team developed a graphical user interface that visually highlights media streams, allowing anyone managing media streams to see and troubleshoot multicast network problems that arise.

The software makes it possible for people and organizations to manage and distribute many kinds of steaming media content. Besides entertainment such as concerts or movies, multicast is idea for enterprises to use for corporate communications such as audio/video conferencing and e-learning, auctions, commercial pricing updates (multicast via satellite uplink) or simultaneous delivery of sensitive information such as stock prices.

In the case of a rock concert, participants would sign up on a Web site before the streaming media content is scheduled to be multicast. When the time comes for the concert to be multicast, one media server could send the streaming content to all those who have signed up in advance or to the latecomers who sign up on the Web site as the event is in progress.

Quote: 'In the future, an artist need not sign with a record label or distributor that can stream content from massive web farms of servers, nor purchase terabytes of network bandwidth for their concert. They can simply multicast from their own PC.'

Concerts and more

The researchers hope the technology will help drive the adoption of multicast by solving the network management issues and media server scalability challenges.

"This product brings new ways to manage and use streaming media within corporations and makes it possible for people to develop new content such as concerts, movies, videos, original music and speeches and share them with a potentially infinite audience," says Perry.

But not just corporations would benefit. Because the upfront cost of the technology is low, the tool can indirectly help solve the distribution problem for artists, traditionally their greatest business dilemma, Perry says.

"In the future, an artist need not sign with a record label or a distributor that can stream content from massive web farms of servers, nor purchase terabytes of network bandwidth for their concert," he says. "They can simply multicast from their own PC."

by Sanjay Khanna



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