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Converged Networks
July 2000

Scot Robertson  

Defining The Voice Landscape


The convergence of data and voice in telecommunications systems is creating a growing list of new services, equipment, and service providers. Technology is racing to fulfill the goal of transparent and seamless voice and data access over a single communication device or channel. This convergence process is complicated by the diversity of existing voice communication systems and the extent of deployment of legacy PSTN equipment. Moreover, merging historically independent data and voice communications systems is confusing to both end users and service providers. Through this column, I hope to allay fears surrounding quality and reliability, explore the needs of the major equipment segments, and help end users and operators make educated choices.

Much of what you read about today regarding Internet telephony technology focuses on when everything will work together. I would like to get beyond the hype and get to the next useful step of implementation. This column will address specific problems and examine issues related to real-world situations and networks that are deployed today. This is important because the issues covered will aim to provide practical information from the service provider perspective to gain an understanding of convergence and how to solve some of the key issues that the industry is working to resolve. Each month, I'll define the problem and provide an explanation of the cause. I will then explain how a particular problem can be managed from a technical viewpoint and provide solutions.

For example, network operators who want to offer multiservice access over their broadband access network, or voice services over their private network, are concerned with managing calls from the IAD (integrated access device) to the gateway, back to the PSTN. The main issues here include connecting back to the PSTN, compatibility, and quality.

A good example of what is going on today with Internet telephony technology as a seamless communication method can be related to the early days of e-mail. As the use of computers has evolved, people used desktop PCs to easily generate information and then used methods such as fax and mail to enable the communication. Then, technology allowed us to combine communication information generation and communication (convergence) through the PC with the use of Ethernet LANs. This required the technology to integrate the communication and the computer simultaneously. This did not happen overnight. There were issues with e-mail, just as there are issues with voice and data convergence in the network. There are complexities to bringing the pieces together that were separate before.

Network convergence is not rolling out across the network at the same pace, much the way e-mail was adopted at different rates. There are limitations on the applications of convergence because of the adoption rates and other technical aspects. With the e-mail example, initially there was not enough bandwidth for sending attachments, or the network was not dependable enough for this application. The issues of convergence that I will examine that are the most pertinent today and the most critical for wide-scale adoption and implementation include QoS (Quality of Service), access, and interoperability.

Quality of Service
The problems surrounding QoS are the grading and service guarantees of the networks used. This relates directly to latency and missing/delayed packets in the network, the main culprits for today's lower-than-desired QoS levels. The question remains, is a guaranteed quality level possible? And, what are the different quality issues and how can they impact the voice system to satisfy the end users? Solutions to these problems are vital in helping plan large-scale deployments.

Access is related to what business the service provider is in. If a service provider wants to offer converged voice and data services, a customer base must be able to be reached and it must be determined how the customer will access the network. There are new ways to access them such as over a cable modem, DSL modem, or dial-up, and old ways including the universal PSTN. The issues are determining what access methods are available to the service provider, and what access method will work for the service provider and the end user.

Service providers offering separate access services use a gateway or concentrator to connect to the network. An alternative is if a service provider uses a connection such as a cable or a DSL. The problem today is that people have access to either voice networks or data networks, so there is a need to add a new "converged network." For instance, by leveraging the PSTN, the end user doesn't access the network directly. The service provider has a converged network. On the flip side, with Web click-to-talk services for example, the user is connected to a converged network. The problem with this application is there may be a limited number of users able to connect or may not have the appropriate equipment or resources. When looking at converged networks, there are issues surrounding converged access from the user to the network (such as bandwidth, interoperability, and reliability), and issues with convergence on the network (such as QoS and interoperability). Can you name what the issues are?

Interoperability is key to enabling convergence from point to point across the network, making sure all parts of the network work together. Issues surrounding interoperability are accommodating bandwidth variations, standardization, and guaranteeing QoS levels between the different parts of the network. Another interoperability challenge is implementing virtual circuits (VC) across different protocols. These can include VoIP, VoATM, VoDSL, VoCable, VoIP PBX, and IP phones.

Whether a provider is using data backbone bandwidth to provide voice services and tap the voice market, or using broadband data access service to tap the voice market, there is huge opportunity and many reasons for being excited about the potential of Internet telephony technology.

An examination of the range of Internet telephony technologies and their benefits will yield a picture of how, when, and where this technology will be deployed. We can then extrapolate to estimate the complete evolution of the converged network. This will take into consideration the growth of networking bandwidth, quality over quantity, and what the applications are that are driving convergence.

The next two columns will provide insight into some of the QoS, access, and interoperability issues facing two real-world applications: Long-distance wholesaling and multiservice access systems.

Scot Robertson is the director of marketing for Remote Access Products at Analog Devices, Inc., a leading manufacturer of precision high-performance integrated circuits used in analog and digital signal processing applications. Scot can be reached at scot.robertson@analog.com.

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