Why SIP Alone Wont Enable VoIP to Cross the Chasm

Posted: 4/2004

Why SIP Alone Wont Enable VoIP to Cross the Chasm
By Martin J. Steinmann

Martin J. Steinmann

When the IETF ratified the

Session Initiation Protocol (SIP) standard, the VoIP industry finally had the baseline for a new wave of interoperable telephony products. Using SIP as the foundation promised to allow enterprise customers to use an IP PBX from one vendor, a media gateway from another and a phone from a third vendor. Customers would be able to choose the right individual products based on their specific needs. But that freedom of choice never materialized, primarily because VoIP hardware suppliers, while playing lip service to the SIP standard, continued to incorporate proprietary features and functionality into their products that precluded these products from true interoperability.

The problem is that SIP alone is just a technology. And while it is the de facto VoIP standard, it is just one piece of the overall answer. SIP needs to be paired with a new business model based on an open, stable infrastructure in order to deliver on its promise of industrywide interoperability. The solution is open source.

Combining an enabling technology with a viable business model is a well-established trend in the PC and server markets. By applying this model to the enterprise telephony market, the combination of SIP and an open-source business model will significantly accelerate VoIP adoption and spur innovation.

Open source has the potential to bring PC-like economics and multivendor solutions to the telephony market, providing the same magnitude of price and innovation benefits to the enterprise customer. Fundamentally, this will force the telephony market to re-examine the current model of vertically integrated, single-vendor solutions to the more open model typical of the IT sector.

Open vs. Proprietary
Open Proprietary
Encourages healthy competition, innovation and interoperability Encourages vendor lock-in, stifles competition, prevents interoperability
Built on open standards, such as SIP Reinvents existing standards such as SIP in a completely different way
Extends existing standards in ways approved by the IETF Extends the standards in incompatible ways with the IETF standard
Invents new technologies and proposes them to standards bodies, accepting feedback and incorporates the feedback into the final standard and implementation Reinvents technologies that are currently in the standards and keeps them proprietary
Actively encourages other vendors to implement the standards-based technology in compatible ways Integrates the technology into its vendor-specific, proprietary solutions, making it impossible for other vendors to implement

Source: Author

Open source, a well-established and successful model in the IT world, has the potential to open up the enterprise communications market, breaking the vertically integrated barriers that force vendor lock-in. Open source no longer just means free. Rather, businessgrade open source is a proven model that provides IT infrastructure customers high quality and innovative software, and comprehensive services and support equal to or better than traditional, closed solutions. An open source business model has become attractive for mission-critical enterprise applications because it is focused on service and support.

Now, open-source is poised to break down the vertical barriers that lock in customers to one-vendor telephony solutions and lock out competitors with products that could spur innovation and drive down costs.

The open-source IP telephony business model bridges two domains  telecom and IT  by replicating a well-established market model within the PC and server market.


The telecommunications market today is vertically integrated. Hardware and software are proprietary. Customers buy their phones and systems from a single vendor. They have fewer choices. Standards, which have been created to promote interoperability, enhanced features and vendor choice, are being polluted as vendors change the standards with their own proprietary hooks. This model prevents true interoperability and commoditization of the market, and prices remain high.


During the 1980s and 1990s, the industrys structure went from vertical to horizontal with the rise of the personal computer. While the industry was no longer vertically integrated, proprietary standards continued to exist that locked customers into single vendors at certain layers. The Linux operating system was a response to that proprietary approach to software operating systems. Its open-source model, where the software and source code are available to download for free, has opened up the operating system market to competition. Today, there is market competition at almost every level.

In a similar way, open source is poised to break through the vertically integrated, proprietary IP telephony market.


SIP is the IETF signaling protocol for global, interoperable presence, messaging, voiceover- IP and audio/video conferencing. SIP began, as its name indicates, as a way to start sessions between users on the Internet. Over the past couple of years, the IP telephony community has adopted SIP as its protocol of choice and it has become the basis for a wide variety of applications. The SIP standard was based on the HTTP model and is becoming for IP communications what HTTP is for the Web.

While SIP has been successful in creating an industry standard, in practice the market has been stymied by the way the protocol is being used. The standard has been polluted as vendors add to the protocol for their own proprietary features. The resulting vendor differentiation and customer lockin is useful to vendors, however, interoperability problems stem from vendors taking different approaches to SIP features. This practice has delayed the widespread adoption of commercial IP telephony solutions.

In addition to the problems with the proprietary implementation of SIP, the vertically integrated market also tends to impede rather than enhance competitiveness. In an open environment, customers will examine each value-chain element when making purchasing decisions and expect widespread interoperability. This is not yet possible in the IP telephony market.

One goal of SIP is that it would open up the IP telephony market to competition, but the promise of a completely open market has not been kept. For the IP telephony market to thrive, it needs an open, standards-based technology as the dominant solution. This requires two things: a broadly accepted technology based on a standard as well as a business model that leads to pervasive adoption. To bring about this widespread adoption, the combination of IP telephony and open source is needed.

Opening up the source code to a larger community of developers is the key to preventing vendor lock-in and creating affordable, interoperable IP telephony solutions. A large community of developers or many eyes brings greater stability and more functionality. With an open source solution, companies will be able to run IP telephony communications software on off-the-shelf Linux servers and use equipment from multiple vendors. The benefits of an open environment include: increased efficiency, based on the use of standardized components that will be mass-produced and greater innovation that comes from leveraging a larger group of technology specialists. Its a solution that fosters competition.

Open-source IP telephony means freedom of choice and cost reduction through vendor interoperability. An open business model will lead to greater competition that will bring about higher quality, more functionality and lower prices. Just as the personal computer split up the vertically integrated computer business, open source IP telephony will do the same in the telecom market.

Martin J. Steinmann is senior vice president of marketing for Pingtel Corp., a manufacturer of IP PBXs.

PingTel Corp.

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