The Future Is On Hold. DOCSIS 1.1 Delayed, VoIP..... later.
Hi ftth,
Here's something on the CableGuysGroupGathering in Chi-town.
eetimes.com
Modem issues put cable voice-over-IP service on hold
By Junko Yoshida
EE Times
(06/15/01, 7:16 p.m. EST)
CHICAGO — While U.S. cable operators are expected to leapfrog their telephone counterparts in offering voice-over-Internet Protocol service, cable industry participants and observers acknowledged this past week that schedules for VoIP deployment have slipped.
To clear a path for voice-over-IP service, cable operators have upgraded two-way hybrid fiber/coax plants and specified PacketCable for real-time multimedia delivery over the cable modem infrastructure. The cost of VoIP deployment should be lower for cable companies than for the telcos, observers said, because cable VoIP service can share the same infrastructure already established for high-speed data services.
But the operators that gathered here for the National Cable and Telecommunications Association (NCTA) conference have put the voice-over-IP rollout on hold as they reshuffle their business priorities and await the standards-compliant equipment required at the head-end and in the home.
"It looks like [cable-based] VoIP services may not start until next year — almost a year later" than the industry had predicted, said Mike Paxton, an analyst at Cahners In-Stat Group.
"IP-based services will be rolled out not in the millions" but incrementally, said Glenn Russell, director of multimedia architectures at cable research consortium CableLabs.
Time Warner Cable, the nation's second-largest cable operator, promised at the conference that it will field commercial VoIP as a secondary subscriber line service within the next 18 months. Charter Communication Inc. said it will start primary-line service next year or in 2003.
But deployment still awaits the availability of cable modems based on version 1.1 of the Data Over Cable Service Interface Specification. Docsis 1.1 was released two years ago; CableLabs began its certification program for compliant products last year. But Paxton noted that no cable-modem vendor has yet received CableLabs certification for Docsis 1.1-compliant products.
The Docsis 1.1 network and PacketCable extensions will allow delivery of data and voice traffic over a single high-speed, quality-of-service (QoS)-enabled broadband architecture. The 1.1 revision provides for what Paxton called "three key elements that must be added to support toll-quality telephone calls: upstream packet fragmentation and reassembly techniques, support for a national clock, and an advanced isochronous scheduling system."
In sharing VoIP trial results at the NCTA conference, most cable operators expressed confidence in the soundness of the fundamental PacketCable technologies. "We've all learned that the technology works and works well," said PacketCable initiative chairman Mark Coblitz, senior vice president for strategic planning at Comcast Corp.
What cable operators need now, he said, is "Docsis 1.1 cable modems and a next-generation cable modem termination system with carrier-grade quality at the head-end." After that, deployment further "depends on the way services are defined and on cable companies' capabilities and priorities," Coblitz said.
Not first, not last
The economy figures into those capabilities and priorities. Glenn Altcheck, director of marketing for VoIP solutions at Motorola Inc., said cable operators are taking stock during the downturn. On the list of services they can offer today, including video-on-demand, interactive TV, high-speed data and streaming video, "IP telephony is not the last, but it's not the first, either," Altcheck said.
Decisions that must be made up front are centered on the VoIP architecture, the media terminal adapter (MTA) to be installed in the home and whether service should be offered as a primary or secondary subscriber line. Providers' choices will affect their capital costs and deployment schedules.
As operators rethink strategies, one question concerns the soft switches that interface with the public switched telephone network (PSTN). The PacketCable specs for VoIP call for the use of soft switches — software run on general-purpose servers to handle functions ordinarily run on costly, Class 5 central-office switches.
Russell of CableLabs said the soft switch is valued for its low-cost, highly flexible, scalable architecture. But cable operators that already own Class 5 switches or that have partnership agreements with Class 5 switch owners are looking for ways to leverage the big-iron fabric switches to offer "switched IP" as an interim step before migrating to soft-switch-based, "full IP" architectures.
Kevin Woods, vice president of product management at TollBridge Technologies Inc. (Santa Clara, Calif.), pitched his company's VoIP gateways as "ideal for cable operators who don't want to make a big investment up front." The product is designed to move voice from an IP network through Class 5 switches.
The soft switch needs to "emulate all the features and performance characteristics that telephone companies have developed over the last 50 years for their telephone switches," Woods said. That could mean "another three years" before the software technology matures.
Approximate functionality
But soft-switch provider Clarent Corp. argues that soft switches can sufficiently approximate Class 5 functionality without looking to replace the big-iron switches. Clarent already offers "the top 22 features of Class 5 switches in addition to some new functions," said Michael Pritz, vice president of local access product marketing at Clarent.
CableLabs is putting together an addendum to the PacketCable specifications to accommodate those seeking to leverage Class 5. Voice gateway boxes, interfacing with Class 5 switches, must be standardized so they can translate data into IP packets that can be understood by the customer-premises MTA.
"We need to define the QoS and security for the rest of the IP-based cable network infrastructure," Woods of TollBridge said.
CableLabs' Russell, however, called the additional standardization work a "minor extension" to the current PacketCable specs and said the work will be completed shortly.
Cable handles voice in a manner similar to digital subscriber lines. DSLs terminate at the central office's DSL access multiplexer (DSLAM); cable systems use a cable modem termination system (CMTS) installed at the cable head-end. In both cases, a gateway box is used to split traffic, sending IP data to the Internet and voice traffic to the PSTN.
Voice gateway boxes such as TollBridge's will extract the original voice signal from a VoIP transmission and forward it to a Class 5 telephony switch using the GR303 standard.
But cable systems require more intelligence in the gateway, in the form of a mini-soft switch, said TollBridge's Woods. "The end result is that the [cable] MTA thinks it's talking voice-over-IP to a soft switch, and the Class 5 switch thinks it's talking to a digital loop carrier," Woods said.
Some people believe a multistep phase-in will leave cable better-prepared than DSL to handle voice-over-IP. Woods said that DSL will continue to rely heavily on Class 5 switches for call signaling on the voice side, making it more difficult to bring those functions into the IP side of the network. Further, the existing ATM infrastructure for DSL doesn't migrate easily to voice-over-IP, since customer-premises equipment may need to be changed, he said.
AT&T, Cox Communications and a few others have rolled out phone service over the cable plant via an approach called constant-bit-rate telephony. The technique uses proprietary head-end and customer-premises equipment and establishes separate infrastructures for telephony and cable modem Internet access. But most current VoIP trials tap a unified, cable-modem-based infrastructure.
Full-IP trials
Both Charter and Time Warner are focused on implementing PacketCable-based VoIP service over the full-IP-based architecture. Charter is engaged in two trials — in Wausau, Wis., and St. Louis — that each involve hundreds of customers, according to Charter senior vice president Majid Mir. The Wausau trial, reflecting a centralized approach, uses Telcordia Technologies' call agent, Cisco's CMTS and Motorola's network interface unit (NIU). The St. Louis trial, involving a more distributed architecture, uses Nortel's call server and Arris/Antec's NIU and CMTS.
"We are testing to see which set of technologies does better in terms of provisioning, managing and recovering the network," Mir said.
Time Warner is also involved in two trials — in Rochester, N.Y., and Portland, Ore. While Charter is looking to field primary-line service, Time Warner is pursuing a value-add to its existing high-speed data service.
"This is not based on a lifeline concept," said Greg Hunt, vice president of operations at Time Warner Cable. Deployment of primary-line service — which under federal regulations is required to run reliably 99.999 percent of the time, even during power outages — would require Time Warner to build redundancies into its system at a cost it is unwilling to shoulder.
For now, Hunt said, the trials have proved VoIP technology works well. But "the Achilles' Heel is in the operational support system."
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So, it appears that the cablecos have decided that for now it is too costly to compete directly with the PSTN on life-line service. ILECs win another round.
And so much for the investor/speculator who thought this would be an overnight sensation. Incrementalism is the new buzz word, eh?
-Ray |
