By Christine Perey
Network World, 5/19/97

If your company regularly holds videoconferences involving three or more sites, you've probably considered purchasing a multipoint conferencing server. To help guide your decision, we looked at products from four leading vendors - which together comprise about 98% of the market - and one clear winner emerged: Lucent Technologies, Inc.'s MultiPoint Conferencing Unit (MCU). It outperformed the others in all categories.

A multipoint conferencing server is an integrated hardware/software network device that permits three or more remote sites to see and hear one another without perceptible delay. Today,all multipoint conferencing servers comply with the International Telecommunication Union H.320 protocol to connect many vendors' products across circuit-switched networks, such as leased lines and ISDN. In time, these servers will perform similar functions for videoconferencing clients on packet-based LANs.

In a multipoint videoconference, people convey a wealth of contextual, nonverbal information to one another. However, if you think multipoint conferencing is like a visit to a ''Star Trek'' holodeck, think again. Currently, the feature set is basic, quality and reliability vary, and manageability ranges from downright awkward to ''emerging.''

The best MCU we tested, Lucent's MCU Release 4.1, derives its processor, memory, backplane, cabinets and software platform from Lucent's Definity Enterprise Communications Server (ECS), a private branch exchange. In many respects, it is more like a PBX than other MCUs based on PC-platform technology. PBXs have proven themselves invaluable for voice communications, primarily because of their reliability and scalability. Lucent's MCU earned our Blue Ribbon for providing the best features for network managers, conference operators and end users. Nevertheless, we think there's room for improvement in the continuous presence implementation we saw, in its ease of network configuration and integration of data conferencing support.

PictureTel Corp.'s Montage bridge is a well-established, full-featured product, but it's relatively difficult to use. PictureTel, like many other vendors uses a VideoServer, Inc. MCS 2000 as its base. It adds support for its proprietary PT724 and SG4 coder/decoders and bundles with LiveScheduler, PictureTel's conference reservation software. We decided PictureTel's Montage, for our purposes, was the best of the VideoServer OEMs to review because of the high-quality enhancements it offers over the base platform.

MultiLink, Inc.'s System 80 1.3 is a new product from a company with extensive experience in the audioconference bridge market. The product's engineers focused on making it easier for users to get in and out of meetings with features that make it a strong contender - especially now that PictureTel has offered to buy the company.

According to MultiLink, its System 70 dominates the audioconferencing service market with more than 70% of the long-distance, noncaptive service bureaus. Its mixed media conferencing counterpart, System 80, uses a similar architecture. It is based on banks of general-purpose display system protocols (DSP), which can perform many functions, depending on the need of an individual conference or individual end points in a conference.

VTEL Corp. is second in market share to PictureTel in the room and group videoconferencing system market, according to Forward Concepts' ''Teleconferencing Markets and Strategies'' report. It has offered the PC-based MCU-II since March 1994. Designed for corporate networks, the MCU-II, now in Version 1.12, has a maximum capacity of 20 ports and lacks some features we consider basic in today's market, such as a choice of conference setup modes, continuous presence and an integrated reservation package (for definitions of videoconferencing terms, see the glossary).

We focused on MCUs designed for organizations with 100 or more video-enabled H.320-compliant end points. The H.320 protocol guarantees interoperability among videoconferencing end points and third-party network components such as multipoint conferencing servers. This is the enterprise-level end of the videoconferencing market; small workgroup systems are just emerging, most of them derivatives of the larger systems.

If you're deploying videoconferencing in more than 40 locations and intend to hold periodic or frequent meetings with multiple locations, these products will suit you well. Organizations with fewer than 30 or 40 systems may want to take advantage of offerings from videoconferencing service bureaus. How do you decide which is best for you?

Net configuration, capacity, scalability

We started by assessing the complexities associated with integrating an MCU into a new or existing network environment and making it operational. We also compared how each system would grow in port capacity and expand in functionality as enterprise needs expand.

Most bridges support ISDN Primary Rate Interface lines. PictureTel's offering on the VideoServer platform was the only vendor that offered a Basic Rate Interface connectivity option in addition to the PRI network interface and inverse multiplexer. This is only an advantage in small configurations of eight or so ports. VTEL requires external devices to connect to any network, making it the least desirable from a systems integration standpoint.

All of the products offer the basic conferencing standards - H.261 for video; G.711, G.722 and G.728 for audio; and T.120 for data conferencing - but Lucent's MCU excelled with support for a number of proprietary video compression algorithms. In addition to the standards, PictureTel's Montage has support for PT724, a proprietary audio encoding algorithm, and SG4, the proprietary video encoding algorithm found in PictureTel videoconferencing group and desktop systems.

All of the vendors offer Windows-based conference management applications. Lucent's Conference Reservation and Control System OpCenter is easiest to use by virtue of its tabbed interface to multiple nested screens and well-designed, logical screen layouts. MultiLink's systems management software uses drag and drop well, but the screen tends to get cluttered with multiple open windows.

We were especially pleased to find that multiple management workstations can connect to a server in the MultiLink, PictureTel and Lucent products. This permits a facility with multiple reservation and management terminals to manage a single bridge without having to move around reservationists.

We found MultiLink's hardware design, which uses eight general-purpose DSPs per board, makes System 80 highly flexible. We could use all available DSPs for 384K bit/sec audio/video processing in one call and use the same resources for audio only in the next call. By comparison, Lucent's MCU and PictureTel's Montage resources are not convertible on demand, which means video processing hardware cannot support an audio-only participant.

The products vary in scalability. For example, if your port requirements consistently exceed the total capacity of a single Lucent chassis - more than 64 ports at 128K bit/sec - you can stack up to four chassis. The VTEL MCU-II does not accommodate expansion beyond 20 ports.

On the software side, MultiLink, PictureTel and Lucent management software is too complex for the casual user to pick up without specialized training. Since VTEL's system is more limited, management is simpler and the software is easier to use.

Administrative features, functions

Lucent and PictureTel have a well-integrated software package for advanced resource scheduling. We believe that such a package should be provided with all products. Lucent's ResCenter and PictureTel's LiveScheduler tools were easy to use and powerful. For example, they tracked all conference room reservations, whether or not video was going to be used. That's a good idea - just because there's no videoconference scheduled doesn't mean the conference room isn't being used. Additionally, ResCenter and LiveScheduler notify participants of a scheduled conference via fax or E-mail. Both provide tight integration with the vendor's directory services and call management tools. LiveScheduler also integrates the reservation process with other tasks, such as call accounting and generating reports with third-party software such as Seagate Software, Inc.'s Crystal Reports and Borland International, Inc.'s Report Smith.

A subset of Lucent's ResCenter, called Web.Res.Now, lets end users employ a Web browser to check on MCU availability and place electronic resource requests.

The four products differ significantly with respect to the ease of call setup. The process becomes particularly complicated when you consider that users may be calling in to a bridge - via single-number dialing or through unique ports assigned for each user - or the bridge may be calling the users. Additionally, there will be different mixes of video/audio terminals and audio-only participants.

VTEL MCU-II's call setup options are limited. For example, it lacks support for single-number dialing, but when a conference needs to begin, it can be initiated without delay. In contrast, the PictureTel MCU offers options such as having the bridge dial out to designated end points at a specified time, having participants dial in to a single number for a conference or a mixture of these. However, many of these modes are not easily accessible; you have to spend too much time closing windows and moving through multiple screens of cryptic options. MultiLink's interface is also fairly complicated, but the use of drag-and-drop operations for placing end points in a conference is intuitive and reliable. Lucent's OpCenter software supports almost as wide a set of options as PictureTel's Montage, but it does it in a clear, no-nonsense way.

During a call, administrators should have tools to isolate and correct problems with the end points or MCU. In addition, administrators may be called on to modify settings during a conference. With the exception of VTEL's bridge, which lacked the flexibility of other products in terms of unique greeting capabilities or a continuous presence option, the products we evaluated provide strong call management tools. However, the PictureTel application seemed to have a number of unnecessary steps or screens.

Lucent's Universal Conference Control (UCC) software provides users with a touch-tone telephone that cant dial in to the MCU and switch from presentation mode to continuous presence mode at the conclusion of a speaker's delivery, view all end points and perform other common tasks.

Lucent's UCC Point and Click is a graphical user interface for the same conference control capabilities, giving a call participant the ability to manage conference views through a separate modem connection between a participating workstation and the MCU.

Keeping track of users' identities and preferences, site configurations and company requirements is an important part of an administrator's responsibility. The products we reviewed all provide directories, which give a reservation agent or call manager easy access to information about room, desktop and roll-about systems, including model numbers and most frequent users. However, all still have a way to go before directory services are smooth and intuitive.

In general, we preferred the approach used by Lucent and PictureTel. Their software associates an individual user with a location and lets you enter conference profiles, specifying preferred data rates, additional equipment and settings, even the people with whom a user collaborates most often.

After a conference, each system retains some data about the end points involved, duration of the meeting and call modes utilized. These are important for resource planning and billing. We were impressed with the report-generating capabilities of the three leaders, but each could stand improvements to automate the process and simplify usage analysis. For example, the management report could be broken out automatically by cost center or department, and the vendors could improve the ability to export data to any report generation tool. All four products use password security for admitting those with the authority to change resource reservations or manage a call. Lucent has a concept of partitioning the MCU resources among different reservationists and setting them up with several levels of security. In general, though, the issue of security has not been paramount because these products were primarily used in service bureaus, where access to workstations is limited. Today, however, security is becoming more important.

Meeting participant features

Take inconference user feedback and messaging, for example. H.243 is the standard that guides the implementation of messaging and conference control in H.320 end points. While bridges with full implementations of H.243 have the ability to provide users with feedback, developers of end-point hardware have failed miserably to implement and support the specification in their equipment.

Therefore, many potentially useful feedback and control options - such as letting users know they are on camera, standardized director control and user security - are unavailable to today's desktop and room conferencing users. The lone exception is the PictureTel Concorde, which supports many, if not all, parts of the H.243 spec. Because the end points generally lack this capability, VideoServer/PictureTel and Lucent responded by providing users with entry and exit tones, adopted from the familiar tones in the audioconferencing world, to indicate their status within a meeting.

Likewise, a well-developed MCU feature set for security is untapped due to limitations in the end points. While password security is specified in H.243, most videoconferencing end-point system manufacturers have failed to implement it.

And forget integrated encryption - no standard algorithm has even been defined. We found two alternative approaches to limiting a conference to known participants. In MultiLink's System 80, a conference operator or attendant can subconference with each caller prior to adding the person to a conference. If the caller is known to the attendant or has some unique way of indicating their authorization to enter the meeting, this can be considered an effective security measure.

In Lucent's MCU, a UCC-enabled user, the conference host, for example, can perform a complete sequential visual screening of all participants. Of course, this only works if the people's faces are known. The other two vendors offer more limited options.

These bridges let us perform director or ''conference chair'' control. But if users are going to view virtual meetings as replacements for face-to-face meetings, there needs to be more. MultiLink's System 80 has a unique feature called subconferencing that lets people confer with each other in privacy. To break in to a subconference, the participant requests a private conference from the meeting administrator off-line (via telephone) or from an attendant monitoring the meeting. The conference attendant creates a subconference and drops in selected participants until they request to return to the main conference. Other participants are aware of the departure and return of those who subconference.

Continuous presence, or the ability to see four independent sources of video in one view, is an important feature - so much so that in the near future, systems without it will fade away. VTEL's MCU-II lacks continuous presence entirely, while the quality of the images sent from Lucent's continuous presence module were substandard. However, a Lucent demonstration of an upgraded version, due this summer, showed resolution at 128K and 384K bit/sec that was on par with the high-quality we saw from the PictureTel bridge.

Though we were not able to evaluate it ourselves, we previewed MultiLink's upcoming ActivePresence, the company's branded version of continuous presence. ActivePresence is implemented by software running on its general-purpose DSPs, in contrast with other MCUs, which require a dedicated piece of hardware and a free slot to accommodate the board to execute the decoding, mixing and encoding of the video. Once the software upgrade is installed in the MCU, any board on the System 80 can support ActivePresence conferences.

In addition to continuous presence, you should determine the cost of hardware or software required to support audio add-on participants - people using a telephone while others are using video and audio. We found that all the MCU manufacturers offer this, but it is standard in the base platform only in MultiLink's System 80. Similarly, while support for T.120 data and application sharing should be standard with MCUs, it remains an optional enhancement. We were told that until all end points are upgraded to support T.120 sessions, this will remain off the base platform configuration.

Continuous presence is still evolving. For example, VideoServer - and as a result, PictureTel - plans to release a transcoding option for its continuous presence module by fall. This option will allow users operating at different bit rates to participate in the same conference.

The quality of video and audio in a conference is as important to the user's satisfaction as the development of conference control options. Most of the conference quality is a function of the video and audio codecs used on the end points. If three end points have low-, medium- and high-quality video and audio encoding technologies, users will perceive the difference. While the MCU is not at fault in any way, MCUs have the potential to adjust the quality of a video or audio stream. For example, they can modulate audio levels when one source is too soft or too loud, or clean up video streams before sending them to other end points. Our testing didn't reveal any major differences in conference quality related to these vendors' MCUs.

Reliability, availability, serviceability

The scores we gave MCUs are based on design specifications, diagnostic tools, availability of replacement parts and support, software upgrade strategies and platform maturity. We researched this with all the vendors, and based on their responses, Lucent's MCU should provide the highest reliability because it is built on PBX technology. Though it should improve over time, the PC platform on which MultiLink's and PictureTel's products are based is just not as robust as a telecommunication system. All the products we examined provide customers with extensive status monitoring tools, and vendors train the conference producers to take extra measures to assure that every user's conference goes uninterrupted.

Products on course