Quality the issue in battle of bandwidth - Industry Trend or Event

CommunicationsWeek International, Oct 23, 2000 by Michelle Donegan

As the battle for control of bandwidth management gathers pace, doubts remain whether the Internet Protocol can deliver.

The battle over bandwidth management is coming to the local network, threatening to leave some local access operators with a cost handicap.

Digital subscriber line (DSL) service providers will soon follow the industry-wide shift to packet-based networks carrying only Internet Protocol traffic. This is because, according to a new market-research analyst report, the protocol is best able to deliver high-speed Internet and other data services.

However, the idea will have to overcome service providers' suspicion and a lack of confidence in IP's ability to guarantee quality of service in the access network.

Education

"You can get quality of service, but people aren't really sure of it," said Ian Rowlands, telecommunications research analyst at Frost & Sullivan Inc., of Mountain View, california. "The market needs to be educated."

IP in the access network is necessary for delivering advanced broadband services, such as video on demand, video streaming or telemedicine applications, according to the analysts' report. IP multicasting, for example, will enable DSL service providers to broadcast voice, video and data.

Since interoperability and support for IP is practically a pre-requisite for any provider of Internet services, the report concludes that using an entirely packet-based network avoids mixing multiple technologies and removes the complexities of asynchronous transfer mode, which would make providing DSL services easier for operators.

Also, there are more engineers able to deploy and maintain IP networks than there are for ATM networks. IP networks are less complex and cheaper to maintain than ATM networks.

"The main drivers for IP over DSL are cost, demand for high-speed Internet connection and broadband capacity," said Frost & Sullivan s Rowlands.

However, there are several restraints that hold back IP over DSL implementations, which stem from service-provider perceptions, technical limitations and equipment manufacturer strategies.

The report says that major vendors, such as Lucent, Nortel, Alcatel and Cisco, have focused on manufacturing ATM-based DSL equipment to protect ATM-switch revenues, but this is changing due to competitive pressures.

According to Frost & Sullivan, the biggest hurdle to the growth of IP over DSL is the perception that it is less resilient and has a lower quality of service than ATM.

Quality

KPNQwest NV, of Hoofddorp, the Netherlands, for one, isn't comfortable with deploying an IP based architecture in its access networks. The company recently launched a pan-European DSL service and has commercial services or trials in seven countries.

But the operator only uses IP in the backbone part of its network because there is enough bandwidth to ensure that all the packets get through, according to Rory O'connor, director of DSL and local access at KPNQwest. He said it will be another two years before IP can deliver on quality of service for the access network.

"IP doesn't offer QoS guarantees, so that's why we use ATM in the access network," said O'connor. "IP is acceptable once you get it into the backbone, but not when you're using other people's leased lines.

"At the moment, there is no obvious case to move voice traffic onto an IP network and voice is an important part of the DSL offering."

Gavin Young, chairman of the technical committee at the DSL Forum, explained that moving to an IP-based platform in a DSL-access network is much more complex than it is in the backbone network.

Access control

"The access network must control traffic so that several users, which are sharing the pipe, all get enough bandwidth," said Young. "You can't just throw bandwidth at it like you can in the backbone, or in the [Local Area Network]." Young rules out IP over ATM as a way to get the best of both worlds because it can become unmanageable and complicated. "But in some scenarios, as in the core, ATM will begin to disappear," he said. Young instead envisions an implementation where IP and ATM co-exist.

"ATM could still stay [in the access network], but it would be dumbed down," he explained.

"ATM would handle QoS, traffic management and policing and perhaps IP would handle the sophisticated networking aspects such as signalling and addressing. The ATM layer wouldn't do anything sophisticated."

The DSL Forum's work on IP and ATM enables functionality with both protocols because there is not one solution that fits all operators.

"You haven't got one vanilla-type of carrier out there," said Young. "[The DSL Forum] wants to minimize the number of variants out there, but there isn't one variant which makes everyone happy."