Handbook of Local Area Networks, 1998 Edition:Applications of LAN Technology Click Here! Search the site:   ITLibrary ITKnowledge EXPERT SEARCH Programming Languages Databases Security Web Services Network Services Middleware Components Operating Systems User Interfaces Groupware & Collaboration Content Management Productivity Applications Hardware Fun & Games EarthWeb sites Crossnodes Datamation Developer.com DICE EarthWeb.com EarthWeb Direct ERP Hub Gamelan GoCertify.com HTMLGoodies Intranet Journal IT Knowledge IT Library JavaGoodies JARS JavaScripts.com open source IT RoadCoders Y2K Info Previous Table of Contents Next Hardware Implementations for Business-Quality Videoconferencing In general, videoconferencing on IP networks is like any other commodity: the customer gets what he or she pays for. The software packages mentioned so far are considered suitable for academic, nonprofit, and perhaps “personal” applications. For now, customers who seek “business quality” video and audio will need to evaluate and select desktop videoconferencing systems that have been implemented in hardware. Video and audio compression hardware for IP-based conferencing is available for Industry Standard Architecture (ISA) as well as Peripheral Component Interconnect (PCI), Sbus interfaces, and all major operating systems. Examples include those offered in Intellect Visual Communications Corp.’s TeamVision family of products (using very large scale integration [VLSI] chips and Mosaic’s own design) and Netscape’s Communique line of products (using an Osprey Technology board and Lucent Technologies’ AVP chips for DSP-assisted compression and decompression of audio and video). Network Interface Hardware All videoconferencing systems require a network interface adapter for LAN or WAN access. Most institutions with intranets or T-1 access to the Internet provide an Ethernet adapter at each desktop. The bandwidth and suitability for video depends on whether this interface adapter is 10BaseT, IsoEthernet, or 100BaseT, and an assortment of network design issues. IP-based videoconferencing can also run locally over Token Ring networks with routers providing connectivity to and from the wide area networks. For those who do not have a dedicated connection to an IP-network, dial-up access to the Internet is accomplished with a point-to-point protocol (PPP) or serial line IP (SLIP) connection via a modem or an ISDN terminal adapter through an Internet services provider (ISP). In general, dial-up IP network interfaces accommodate consumer applications adequately, but are not suitable for business-quality video and audio supported with specialized hardware. VIDEO-READY NETWORKS In the previous connectivity scenarios, an Internet communications protocol stack in the host operating system negotiates and monitors connections. This section, however, focuses on the steps needed to address bandwidth, as well as the IP facilities and the internetworking software commonly used and currently being proposed for desktop videoconferencing in IP environments. Network Upgrade and Management Issues Preparing a network for any new application, including multimedia, requires careful analysis of existing components and user requirements. As far as network upgrades for videoconferencing are concerned, an intranet is quite different from the public Internet. In the private network (e.g., intranets over LANs, MANs, VANs, and WANs), technologies can be more consistently deployed, more effectively maintained by a central IT group, and often more economical to purchase when large-site licenses are negotiated. This said, jurisdictional (i.e., workgroup) management of LANs is increasingly popular. In contrast with the situation in LANs and private WANs, new protocols and architectures take much longer to deploy in the public/commercial IP environment. There is an inherent lack of control in this progress, especially if there are new management challenges associated with upgrades. Video-enabling upgrades clearly fall in this category. One way for LAN administrators and managers to approach the design of a video-ready network is by working from the end-points toward the common infrastructure (e.g., the Internet). End-Point Performance Initially, users and planners should evaluate the end-point CPU performance. If the CPU is involved in any general data application management and compression or decompression tasks (which is almost always the case in the desktop videoconferencing applications distributed as freeware, and less the case when add-on compression hardware is necessary), then low performance at the desktop will translate to poor quality of service and less efficient bandwidth usage patterns. When end-points are enhanced and capable of compressing video frames, bandwidth will be more efficiently utilized between desktops. Network bandwidth requirements for desktop videoconferencing vary with applications as well. Some applications—especially precision medical or surgical applications, or high-quality entertainment and advertisement production—require many megabits per second to transmit lossless (i.e., compressed without any loss of information) or nearly lossless video between points. In most business scenarios, however, the combination of efficient compression algorithms, network management software, and user tolerance of less-than-TV-quality video keeps the bandwidth requirement (per bidirectional session) between 28.8K bps and 768K bps. Because, in general, users’ lowest level of tolerance is the highest performance they have had the privilege of using, it is safe to assume that IP networks in place today need modification to deliver acceptable business-quality video in real-time. On a shared network, such as an Ethernet, Token Ring, or fiber distributed data interface (FDDI) network, or the commercial Internet today, all stations have equal opportunity to send and receive data. This is known as “time division multiplexing.” Several options exist for changing network designs to accommodate the demands of streaming data types. One of these is to supplant or augment best-effort protocols in order to prioritize video and audio streams in such a way that end-points receive consistently low latency. This approach is discussed in greater depth a little later in this chapter. If, prior to changing the data management, an enterprise decides to deploy high-speed LAN technologies (e.g., 100BaseT, 100VG-AnyLAN, ATM), there also needs to be upgrades to WAN infrastructures. Options and issues in this arena are the focus of many books and current articles, and outside the scope of the present chapter. Previous Table of Contents Next Use of this site is subject certain Terms & Conditions. Copyright (c) 1996-1999 EarthWeb, Inc.. All rights reserved. Reproduction in whole or in part in any form or medium without express written permission of EarthWeb is prohibited. Please read our privacy policy for details.