RiverDelta Tries Scalable Approach

RiverDelta Networks Inc. is adding a bundle of new technology to its cable-modem-termination-system chassis designed to help MSOs deal with one of the largest challenges they face when it comes to preparing networks for multiple ISP access: scalability.

"Today, open access is not done in a scalable manner," said company vice president of marketing Jeff Walker.

To bridge that gap, RiverDelta said it will add source-based policy routing and multi-protocol label switching (MPLS) capabilities to its Broadband Services Router 64000, allowing operators to monitor and control individual traffic flows for multiple services and providers. RiverDelta has proposed that cable operators distribute its gear at network edges, essentially creating a web of "label edge routers."

MPLS, an Internet protocol standard, defines quality of service for each particular packet flowing across the network. In that scenario, each packet is classified at the CMTS, then quickly routed to the ISP point-of-presence to which it belongs via a defined label switch path.

Those paths can be defined ahead of time either manually or automatically via reservation protocol or the emerging label distribution protocol, Walker said.

"MPLS is clearly the most elegant way to distribute policy-based routing in an IP-optimized environment," Kinetic Strategies Inc. president and broadband analyst Michael Harris said. Cisco Systems Inc., which contributed to the original standard, also is a "big fan" of MPLS, he added.

The standard also will grow in importance as the cable industry moves beyond best-effort data services and begins to employ QOS for tiered high-speed services and voice-over-IP applications. Without QOS, for instance, a cable operator would not be able to prioritize latency-sensitive VoIP packets over typical Web browsing packets.

MPLS also eliminates the need for "tunneling," a fast protocol used by America Online Inc. Critics of tunneling maintain that it would "hide" what type of content (video, voice or data) is flowing through a hybrid fiber-coax network from the operator, eliminating its ability to implement QOS.

Policy-based routing plus MPLS "will raise the bar on policy-based routing used today, and implement more scale," Walker predicted.

Centralized, software- and policy-based routing schemes used in early open access trials have demonstrated that traffic from several ISPs is possible, but on a very limited scale.

AT&T Broadband senior vice president of advanced broadband services Susan Marshall acknowledged as much during a briefing last month. She said existing technology has inherent scaling constraints, and estimated that the MSO today could accommodate no more than 10 ISPs on a particular system before encountering network degradation problems

AT&T likely will need better technology as it widens the availability of its "Broadband Choice" product in Boulder, Colo., and readies for a larger rollout this fall in the Boston area.

Time Warner Cable, which is conducting a multiple ISP trial in Columbus, Ohio, is taking a close look at MPLS on a test network also in that city.

"Part of our plan is to try it out on a larger scale," Time Warner Cable vice president of networking engineering Michael Adams said, noting that executing policy-based routing from a centralized location does not scale very well.

By distributing it to the CMTS, "the performance is much more scalable," he said.

MPLS isn't the only approach equipment vendors are proposing.

Celox Networks, a start-up based in Southborough, Mass, believes it's more cost-effective for cable operators to handle multiple ISP routing at the cable network's aggregation point rather than at the distributed CMTS.

High capital costs would be incurred if an operator decided to install upgraded CMTSs across the network, explained Celox senior vice president of marketing and business development Hugh Kelly.

By handling open access via a subscriber-management system at a network's aggregation point, operators would have to replace one device instead of swapping out several, he added.

To date, most of Celox's focus is with traditional carriers. The company is preparing to launch a trial with AT&T Global Network Services in mid-May, Kelly said, noting that Celox's equipment is being designed to accommodate digital-subscriber-line, cable and fixed-wireless networks.

Celox's proposition "makes more sense in a DSL or dial-up environment," because it would negate the benefit of cable's dedicated, "always-on" broadband access, Harris said.

When it comes to scalable open access over a cable network, "MPLS is the preferred approach," Adams said.