Riverstone recasts multicast

Riverstone Networks Inc. this week enhanced the multicasting capability of its metropolitan area network routers in an effort to better support video and streaming media applications.

The extensions to Riverstone's implementation of the Internet Group Management Protocol (IGMP) are designed to manage group membership of video streams down to the set top box. This offers carriers an opportunity to introduce new services, such as video over DSL, interactive digital TV, and other streaming media, in which subscribers within a single household can view different channels at the same time, Riverstone says.

IGMP outlines the method in which subscribers are added or removed from different channel groups. It, and the method for tracking group membership by port, is defined by IETF RFC 2236.

Citing data from market research firm Yankee Group Inc., Riverstone says video offerings, such as broadcast TV, video-on-demand, interactive TV, and video conferencing, can more than double carrier revenue opportunities from broadband customers receiving only high-speed Internet access services today. But to deliver video services over DSL with the same quality as cable service, carriers need an IGMP implementation that's faster and more scalable than today's, Riverstone argues.

Currently, the maximum acceptable time for channel changes is 500 milliseconds. Riverstone's souped-up IGMP moves subscribers between groups in 40 milliseconds, the company claims.

Riverstone enhances RFC 2236 to provide what it claims is a greater level of granularity that can track membership down to the set top box.

The company's IGMP-enabled routers maintain a database of different multicast groups or channels. When subscribers change channels, Riverstone routers update the database and direct the new video streams to the subscriber.

Texas-based Livingston Telephone recently deployed a video over DSL system Riverstone co-developed with Advanced Fibre Communications Inc., Myrio Corp. and Minerva Networks Inc. Riverstone's extended IGMP implementation enables Livingston to deliver interactive digital TV, video on demand, pay-per-view sports, gaming and other services over the telephone connection that exists in almost every consumer household, Riverstone claims.

Livingston Telephone is looking to become one of the first U.S. carriers to deliver video over DSL services to its subscribers.

Riverstone's IGMP play is in keeping with the norm for the metro router market, according to research firm Current Analysis. Support for a wide variety of routing protocols, and for quality of service, rate limiting, VLAN, and multicasting capabilities is typical in this class of device, the firm states in a recent report.

"Port density and footprint remain important, but increasingly, carriers demand support for differentiated, billable services compatible with legacy infrastructure," states David Dunphy, a Current Analysis analyst and author of the report.

As greater numbers of differentiated IP-based services are considered by carriers, the packet processing capabilities of Ethernet routers in the MAN are increasingly important in order to support low latency as well as high throughput, Dunphy states.

Current Analysis Inc. ranks Riverstone as a "second tier" supplier of metro routers, while Cisco Systems Inc. and Nortel Networks Corp. are ranked "1st tier" by the firm. Joining Riverstone as second tier suppliers in this market are Extreme Networks Inc. and Foundry Networks Inc.

Current Analysis maintains a neutral/positive stance on Riverstone's current success in metro routers, and in its momentum. The firm is "positive" on Riverstone's vision in this market.

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