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Chapter 19
Voice and Video on the LAN

Martin Taylor

Voice and data convergence in the LAN is about to become a hot topic in the industry, thanks to advances in switching and processors, as well as the H.323 standard. This chapter first looks at the business reasons for considering the deployment of voice and video over the LAN and then discusses the technical issues and requirements.

INTRODUCTION

Most desktops in enterprises today are equipped with two network connections: a LAN connection to the PC or workstation for data communications, and a phone connection to the PBX for voice communications. The LAN and the PBX exist as two separate networks with little or no connectivity between them. Each has evolved to meet the very specific and differing needs of data and voice communications, respectively.

Despite much talk in the industry about the convergence of computers and communications, LANs and PBXs have not really moved any closer together during the last decade. In the mid-1980s, some PBX vendors sought to bring data services to the desktop via ISDN technology, but the advent of PCs requiring far more than 64K-bps communications bandwidth favored the emerging LAN standards of Ethernet and Token Ring. So far, most LAN vendors have not attempted to support voice communications on the LAN. But all this is about to change.

There are three key factors at work today that suggest that voice and data convergence in the LAN is about to become a hot topic in the industry:

  The widespread acceptance of advanced LAN switching technologies, including ATM, which makes it possible for the first time to deliver reliable, high-quality, low-delay voice transmissions over the LAN.
  The emergence of the first standard for LAN-based videoconferencing and voice telephony, H.323, which removes objections about the use of proprietary protocols for voice and video over the LAN.
  The deployment of the latest generation of Intel processors, featuring MMX technology, which makes high-quality software-based, real-time voice and video processing feasible for the first time, and the new PC hardware architectures with Universal Serial Bus that permit voice and video peripherals to be attached without additional hardware inside the PC.

This chapter first looks at the business reasons for considering the deployment of voice and video over the LAN, and then discusses the technical issues and requirements.

THE VALUE OF VOICE AND VIDEO ON THE LAN

There are essentially two main kinds of motivation for considering voice and/or video on the LAN: the need to support new types of applications that involve real-time communications, and the desire to improve the overall cost-effectiveness of the local communications infrastructure.

New Types of Applications

Desktop videoconferencing, real-time multimedia collaboration, and video-based training are all examples of new kinds of applications that can benefit from the delivery of voice and video over the LAN.

The uptake of desktop videoconferencing has been held back by a combination of high costs and the difficulty of delivering appropriate network services to the desktop. Standards-based H.320 desktop videoconferencing systems require costly video compression and ISDN interface hardware, as well as the provision of new ISDN connections at the desktop alongside the LAN and the phone system. New systems based on the H.323 standard and designed to run over the LAN will leverage the processing power of the latest PCs and the existing switched LAN infrastructure, to lower cost and simplify deployment dramatically.

Desktop videoconferencing may be used either to support internal meetings and discussions between groups located at remote sites, or to support direct interaction with customers and clients. For example, some enterprises in the mortgage lending business use videoconferencing to conduct mortgage approval interviews with potential borrowers, so as to greatly reduce the overall time to complete a mortgage sale.

Real-time collaboration applications, involving any mix of video and voice with data conferencing to support application sharing and interactive whiteboarding, provide a new way for individuals and small groups to collaborate and work together remotely in real-time. This emerging class of applications, typified by Microsoft NetMeeting, is being evaluated by many enterprises, particularly for help desk applications.

By contrast, video-based training is already widely used in enterprise LANs. By delivering self-paced video learning materials to the desktop, training needs can be met in a more timely and less disruptive fashion than traditional classroom methods.

The growing popularity of these kinds of applications should be noted by network planners and designers. A preplanned strategy for local LAN upgrades to support voice and video will reduce the lead time for the deployment of these applications, and enable the enterprise to move swiftly when the application need has been identified, to obtain the business benefits with the least possible delay.

Infrastructure Efficiencies

A single local communications infrastructure based on a LAN that handles data, voice, and video has the potential of costing less to own and operate than separate PBX and data-only LAN infrastructures.

The average capital cost of a fully featured PBX for large enterprises is between $700 and $750 per user, according to a leading U.S. telecommunications consultancy, TEQConsult Group. Furthermore, this is expected to rise slightly over the next few years as users demand more sophisticated features from their phone system. It is not difficult to see how a switched LAN that has been enhanced to handle voice could provide a solution for telephony at a fraction of this cost.

Most large PBX installations are equipped with additional facilities such as voice mail and Interactive Voice Response systems for auto-attendant operation. These systems are typically connected directly to the PBX via proprietary interfaces, and they too represent major capital investments. With voice on the LAN, such voice processing applications could be based on open server platforms and leverage the low-cost processing power and disk storage that is a feature of today’s PC server market, thereby lowering the system’s capital cost still further.


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