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February 1999


Which of the current crop of "standards du jour" have shown the most promise? Which standard(s) do you feel is (are) the most significant for the successful implementation of Internet telephony? (Part I)

We asked several industry-leading vendors for their views on the Internet telephony industry. Their responses appear below.

Note: Due to the sheer volume and quality of responses, we have separated the responses to this question into two parts. Part II will appear in the March issue of INTERNET TELEPHONY�.


The development of standards is critical to the mainstream adoption of Data Telephony as a widely implemented form of voice communications. Given the number of developers of this technology, combined with the variety of potential carriers (telecom providers, cable companies, ISPs, next-gen telcos and corporate enterprises), interoperability will be vital to have seamless connections between voice-enabled data networks worldwide.

Therein lies the challenge. Certain standards sacrifice the functionality consumers have come to expect from their RBOC service or business PBX system - call hold, call forward, call wait, call transfer, three-way calling, and more. Such functionality is vital to the widespread adoption of Data Telephony because consumers and businesses will not accept degradation in service. Many of us in Internet telephony are adopting H.323 - originally a multimedia application - as the standard, which does enable interoperability, but is an inhibitor to providing many of the features the market expects from a phone system or service.

It appears that H.323 will be the standard VoIP companies adopt over the next twelve months. That said, Data Telephony might evolve past H.323 if a standard can be found that provides interoperability as well as equal (if not superior) functionality to today's most advanced phone systems. For that reason, SGCP & MGCP will also contend strongly since each centralizes intelligence and control. This makes the access point "dumb," thus lowering costs and enabling higher feature functions - which is a strong fit for the model of cable service providers and other next-generation telcos.

- Robert A. Veschi, President, CEO, and founder, e-Net


I'm encouraged by the IP telephony standards efforts in progress today. Yes, there are overlapping - even competing - standards being developed. But, both service providers and equipment manufacturers acknowledge Metcalfe's law, which states: The value of a network increases as the square of the number of people who can use it. In other words, the value of my IP telephony service increases dramatically when there are more people I can call.

So, while companies jockey for advantage, no one wants to be left behind. Everyone already agrees on basic media streaming using RTP. The IETF efforts to develop a Media Gateway Control Protocol (MGCP) assume this new protocol must interoperate with devices using H.323 and Session Initiation Protocol (SIP) standards. Even competing standards like H.323 call control and SIP can be made to interoperate using a relatively straightforward software stack running on the endpoint, the gatekeeper or any nearby server.

So, unlike fax, where the industry languished for decades before achieving interoperability (and explosive growth!), the IP telephony industry has focused on interoperability from the start. Despite diverse commercial and political origins, each "competing" standard envisions ways to interoperate with other standards. The signs are good. The industry potential is enormous.

- Brough Turner, Senior Vice President of Technology, Natural MicroSystems Corporation


The race to provide carrier-class VoIP equipment is well underway. With the large networking incumbents (with their proprietary hardware) looming, the computer telephony industry has rallied behind the open-systems approach. In support of this open-system architecture, the success of several standards is critical. First, H.100 promises to extend the density of today's MVIP and SCSA systems to levels required by carrier-class applications. At the same time, H.100 unifies the development of open-systems hardware under one standard, an important step in the evolution of PCM bus standards.

Building on the H.100 foundation, CompactPCI systems incorporate features for the deployment of mission-critical systems. For such systems, H.110 and PICMG's CompactPCI Hot Swap Specification provide the specifications and definitions that allow for multivendor support of the open system carrier class VoIP market.

In addition, the industry is working hard to speed the deployment of VoIP systems by recognizing the importance of SS7 in the transition from circuit-switched to packet-switched networks. Two new standards, SGCP and IPDC, build on the momentum of H.323 by incorporating carrier-class features and SS7 functionality. In providing for interoperability with SS7, these standards hold promise to eliminate a critical obstacle in the widespread deployment of VoIP carrier-class systems and services.

- Jason Macres, Vice President of Marketing, DSP Research, Inc.


It's important to understand that IP telephony is a broad area, encompassing everything from voice compression algorithms to Web-browser applications to integration with the existing SS7 telephone networks. While there are indeed many IP telephony standards, most of these are focused specifications that address one part of the whole.

At the voice compression/decompression level, the G.72x series of vocoders has become well established and implemented in a wide variety of hardware products, desktop operating systems, and browsers. At the call-switching and Web applications levels, the H.225/H.245 standards have also become well established for a number of phone-to-phone and PC-to-phone applications. (These, along with the G.72x series vocoders, are part of the umbrella H.323 specification.) Successful H.323 interoperability testing has already taken place between the likes of Cisco, Lucent, VocalTec, and many others.

For fax, T.38 has recently been approved and is expected to be the protocol for real-time fax over IP networks. Quality of Service (QoS) is an important area where standards have not been established but work is ongoing.

The remaining area of divergence is between H.323 and alternatives such as MGCP for large-scale public networks. H.323 was originally designed for small-scale, media-rich, videoconferencing and may have trouble scaling to public network environments in which thousands of calls are established simultaneously. In these environments, it's likely that one of the alternatives will prevail. But having different standards for fundamentally different application spaces is not exactly a Tower of Babel, so long as they share common underlying components, such as the vocoders.

Worldwide deployment of IP telephony requires global standards for signaling, QoS, and coding. H.323 is likely to yield to MGCP for large networks; Diffserv or something similar is likely to emerge for QoS; and one of the G.72x vocoders is likely to emerge as the preferred one in the marketplace. And T.38 is the protocol for facsimile.

- Dave Duehren, Vice President Research & Development, Brooktrout Technology, Inc.


Initially, the IP telephony industry suffered from a lack of supported standards. However, today the industry is hindered by too many competing standards, a situation, which poses a real threat to its future. Never has it been more difficult for both vendors and prospective IP telephony service providers to decide which equipment and features are needed in order to create a viable, scalable and profitable business model.

Despite the multitude of standards, two have emerged that show the most promise: H.323 and MGCP (Media Gateway Control Protocol). These two standards will allow both interoperability and high-value IP telephony solutions to flourish.

The momentum associated with H.323 is strong. Many service providers generally view it as the only viable standard by which interoperability can be achieved. Further, organizations such as TIPHON are working to solve important industry issues. Real-time fax (T.38), gatekeeper-to-gatekeeper communications (Annex.G), as well as a standard call detail record format are all important achievements needed to realize ubiquitous interoperability. Vendors who are demonstrating their commitment to H.323 compliance, while delivering value added functionality via proprietary means will be the winners in the industry.

The IETF's efforts with MGCP are also gaining momentum. The support for MGCP by players such as Bellcore, Cisco, and CableLabs, along with the recent efforts within the IETF surrounding the call control component and its SS7 interworking potential leads Vienna to believe that this standard will be widely supported.

Vienna Systems is committed to open standards, and feel that these standards are critical to the success of the IP telephony industry. As the industry continues to evolve, so too will the standards supported within it. Vienna will continue to leverage its unique distributed architecture to rapidly align itself with emerging open standards.

It is critical that vendors not become totally consumed with competing standards, and "take their eye off the ball" with regard to moving the industry forward from a solution point of view.

- Jim Udall, Vice President of Technology, Vienna Systems Corporation







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