IP Railroad Delivers New Service Set


Top engineers at some of cable's largest MSOs are now implementing strategies to deliver Internet protocol telephony and tiered data services as natural evolutionary extensions of the DOCSIS-based IP platform laid down several years ago.

Cox Communications Inc., Time Warner Cable, Charter Communications Inc., Comcast Cable Communications Inc. and Insight Communications Co. are all eyeing or in the advanced stages of testing Data Over Cable Service Interface Specification 1.1-qualified gear allowing for tiered data services and IP telephony to residents and businesses.

The key issue cable engineers must face going forward is: "How do we continue to leverage this incredible technology that we have to drive more and more capability out of our networks?" said Comcast senior vice president, strategic planning Mark Coblitz.

The answer — for 2002 at least — is evidently a combination of video-on-demand and DOCSIS 1.1.

Indeed, beginning late this year and continuing throughout 2003, IP telephony could enjoy the same amount of activity seen on the VOD front in 2001 and 2002.

AOL senior executives have talked fondly of IP telephony service over cable plant and have charged Time Warner Cable engineers with the task of making that a reality.

"We're moving forward to DOCSIS 1.1 at this point," said Paul Gemme, senior vice president, network engineering, engineering and technology at TWC. Gemme said that platform was essential for a significant voice over IP launch.

The company currently is testing various cable-modem termination systems.

TWC has tested VoIP in Portland, Me., and Rochester, N.Y., using DOCSIS 1.0+ software and a Cisco Systems Inc. CMTS, Gemme said. "The DOCSIS 1.1 is going to give us true quality of service and allow us to better segment bandwidth, or phone traffic away from high-speed data traffic so it won't interfere at all with the other.

"By this summer, we'll be doing trials on at least one or two various CMTSs that are 1.1 qualified," he said. TWC's goal is to launch IP telephony service by year's end.

The company plans to market the service as a second-line service with 911 capability, long-distance, voice messaging and other features — not to mention better pricing and service than the incumbents, Gemme said. Selling it as a second-line service eliminates the need for expensive backup power, Gemme said.

"When we've reviewed it, it's been a very costly situation [because] it's also backing up the powering to the homes," he said. "You have to power to the home from the plant, and that's where it gets real expensive."

According to Gemme, the trick isn't powering only the homes that take telephony. Each node requires power whether penetration was 10 percent or 50 percent. "You can't continuously go in and re-engineer your plant. That's why we've always looked at it and said we're not quite sure how these MSOs could justify that kind of capital investment ubiquitously across the network. Because the day you put on customer one, all that stuff has to be in place.

"We're not going to standby the unit in the home. We're not going to power the unit in the home," he added. "The unit will be powered from the home. Now potentially they could have an option to do a battery back up for the unit in the home."

TWC will use softswitch and a gateway to interface with existing local phone companies, Gemme said. But TWC receives an additional benefit from its sister company, competitive local exchange provider Time Warner Telecom. That company has class five switches in about half of TWC's markets, as well as access to the nationwide backbone used by AOL and Road Runner.

In theory, that would allow an IP telephony customer in TWC's Austin, Texas, system to call a relative in the company's Albany, N.Y., system without leaving TWC's network. "On-net calls are a big benefit," Gemme said. "We have some divisions that are very close to each other in some states."


Cox and Comcast are taking slightly different approaches to IP telephony. Cox currently has more than 500,000 circuit-switch phone customers. But it's testing IP telephony in Oklahoma City, blending the service with its existing circuit switch plant.

"In Oklahoma City, we have placed a GR 303 gateway between our existing circuit switch and potential voice over IP customers," said Cox chief technology officer Chris Bowick. "That allows us to leverage that switch, and provide a VoIP infrastructure on the line side of that switch, and perhaps can allow us to expand the geographic reach of that switch in Oklahoma City."

Cox also wants "to look at any functionality that voice over IP might offer to our subscribers that we can't currently offer on circuit-switched," Bowick said.

"We would like to do a market trial, looking at a second-line scenario. We've certainly got network powering there, but if we want to put an MTA [multimedia terminal adapter] in somebody's home that is not network-powered, that in our mind would not be a primary-line service. The thought is might we want to put some MTAs out there and look at a second-line service from a marketing trial standpoint?" he added.

The company also hopes to test an overlay softswitch solution by year's end, both in existing switched markets and in non-switched markets. "The intent there would be just to stay in very, very close contact with the softswitch vendors to make sure we understand their value implications from a cost and a feature and functionality perspective," Bowick said.

"It's important to understand the difference between circuit-switched and IP from a geographic basis," he added. "Because of the nature of a switching fabric in the circuit-switched, and because of the synchronous nature of the internal workings of the switch, the further you remove a customer from the physical location of that switch, the more difficult it is to service that customer only because there's a finite amount of transit time from the bits leaving the home to the bits arriving at the switch," Bowick said.

Such timing issues basically establish a geographic region, typically citywide, within which a switch will operate, he said.

Since IP is asynchronous, it doesn't depend on the timing of bits, which are pieced together at the other end. "The result of that is that voice over IP, or softswitches, or even a GR 303 gateway on the line side of the switch, can actually serve a larger geographic region," Bowick said.

"Let's say I've got several markets out there that because of the cost of a switch, would not necessarily be markets that I'd like to launch in. Let's say a DMS 500 has a switch capacity of about 100,000 lines, and I wanted to go into a market that in my wildest dreams I wouldn't be able to fill up that capacity on that switch," he said.

"But what if I could place a GR 303 gateway in front of that switch, and I can extend the reach into markets outside of the market in which that switch is located?" he continued. "I can gain the efficiencies of using the full capacity of that switch, which would be potentially 100,000 lines."

But smaller Cox markets, such as those the company bought from TCA Cable TV Inc. several years ago, could feed into a regional class five switch.

"We have this national OC-48 backbone. That's 2.4 gigabits per second," Bowick explained. "We do have some OC-12 and some OC-3 spurs coming off the backbone. But that OC-48 backbone interconnects 11 regional data centers, three service data centers, which is where we house things our high-speed customers use like news and web space. All of this is now interconnected nationally, for the first time."

That means those regions are "no longer independent islands from a technologies perspective."

"Now, take everything that we've talked about on voice over IP and apply it to this national backbone, and the extended geographic reach of a voice over IP either softswitch, or GR 303 gateway," Bowick said. "What if, using either softswitch or GR 303 gateway solutions, I can co-locate at either of my three service data centers, or my 11 regional data centers and use that infrastructure and expanded geographic reach of softswitch or GR 303 technology to serve, in an overlay fashion, all of my markets using that backbone."

Cox also could use that national backbone, instead of its current frame relay system, for MIS communications between systems and headquarters in Atlanta, he said.

"We can do all of that without stranding any of the capital infrastructure that I've put in place on the circuit-switched side. All the network infrastructure that's out there will exist, all of the back office infrastructure, all of that can remain in place. And I'm not obsolescing the circuit switches. I'm just finding a way to more efficiently utilize what I've already got out there, and are doing quite well with already," Bowick said.

He pointed out that circuit-switched and IP aren't parallel systems. "We've got a high speed-Internet infrastructure in place today, voice over IP would ride on top of that. It would fully utilize, in a GR 303 gateway solution, the existing switch and back office infrastructure."


Comcast is testing IP telephony both in its labs and in the Detroit, where Comcast has circuit-switched telephony customers.

The Detroit trial tests IP from the headend to the home. "The IP that is being tested there is not call management servers, which I have in our laboratory here. Today in my lab we have [eight] call agents for IP telephony," Coblitz said.

"You want to look at how you can get the cost structure and some of the savings of using IP from the headend to the home," he said.

Comcast acquired the Detroit footprint, with its class five switch, as part of its merger with MediaOne Group Inc.

So far, Comcast likes what it sees in Detroit. "We proved that this technology can technically work, that the cost structures of being several hundred dollars less in capital, to be workable," Coblitz said. "The quality that was delivered to the customer was not much different from circuit-switched."

The MSO is also a big fan of battery powering. "It's very expensive to network power," Coblitz said. "It has all kinds of issues of building it and you should look at every alternative. Network powering is a per-home task cost. A battery back up is a per-subscriber-that-takes-your-service cost. The people who had originally put in the circuit- switched solutions over cable didn't have these sets of options in any significant way, but today we do."

DOCSIS 1.1 also paves the way for tiered data services, as well as IP telephony. "It's certainly our intention to be buying DOCSIS 1.1 equipment" after testing is complete, Coblitz said.

"What we'll do is start acquiring 1.1 CMTSs and move CMTSs that happen to be there out to other places that need capacity, therefore buying our capacity in 1.1," Coblitz said. "And then learning all the operational sets of issues that we have to do with the increased security and privacy that comes with 1.1, the way to handle quality of service, the way we handle the monitoring of the network. And then once that's under our belt, continue to move 1.1 into other marketplaces."

In addition to tiered data services, Coblitz said Comcast plans to experiment with different forms of streaming media that would have better quality of service over the DOCSIS 1.1 platform.

"There's a belief that some amount of video is going to be occurring over that IP structure. So the question really becomes learning what are the sets of issues and dealing with this over that IP structure and that's DOCSIS 1.1," Coblitz said.

Cox, on the other hand, has been upgradable for a long time. "We have previously announced relationships with both ADC and with what was River Delta, now Motorola, on the CMTS side with their 1.1 capable CMTSs. We're well on our way toward putting product in place that is upgradeable to 1.1," Bowick said.

"We can do a tiered service level today without DOCSIS 1.1 in the plant. If I wanted to offer 128K symmetrical service on DOCSIS 1.0, I could do that today. What it would not be is a guaranteed bit rate into the home."

According to Bowick, Cox will look at tiered services for both commercial and residential customers. "On the residential side we would certainly be looking at a tiered level of service to provide more choice. In our discussions internally we have not yet finalized the price, or an actual tier structure. We want to do some controlled experimentation on price point and tier levels, so that we understand what it is that our customers want and need."

Insight also is looking at the 1.1 platform. "We've got one of the River Delta — now Motorola — CMTSs that we have been doing some testing with off the @Home Network," said chief technology officer Charles Dietz. "We need to increase the memory on some of the CMTSs that we've got as part of that."

Why? "It's quality of service that's going to be one of the bigger drivers where you can go in and guarantee a level of bandwidth satisfaction to the customer," Dietz said. "We would like to get in and start offering a better level of service at a different rate for people that would like to enhance the experience, get more into games, whatever."

EYE ON 2.0

Engineers also are looking ahead to DOCSIS 2.0 certification.

"When I move to 2.0, I gain some additional spectral efficiency. I can cram more bits into the bandwidth available, more bits her hertz, and as a result I just get more efficient in the way I utilize bandwidth," said Bowick.

"So that for me is important as more and more services perhaps migrate to IP over time, and I just need to be more spectrum-efficient. I see value in 2.0, and I see value in the way [Cable Laboratories Inc.] has done 2.0, which is to make it forward and backward compatible with DOCSIS 1.1 and 1.0," he added.

Comcast is also very excited about DOCSIS 2.0. "It will open the door for some sets of services that otherwise would have been more difficult for us to deliver," said Coblitz.

Video telephony is one example, "where we need symmetric at higher data rates than we might otherwise be able to deliver consistently given the amount of upstream bandwidth that we've had. DOCSIS 2.0 relieves a fair amount of that congestion issue," he said.