Voice over Internet Protocol is swimming in a stew of proprietary protocols -- including standards that are too new to provide interoperability and others that lack the functionality to be useful much longer.
Navigating the standards used in voice over Internet Protocol (VoIP) can be a bit of a headache for IT managers, said Mike Robinson, CTO of Citel Technologies, a Seattle-based provider of VoIP systems. "The swirl of competing standards creates fear, uncertainty and doubt in the minds of buyers," he said.
There are numerous standards that vendors and users need to consider with VoIP systems. While these standards are bit messy today, they are likely to be in very good shape in just a matter of a few years.
H.323 functionality comes up short
The most used VoIP standard today is H.323. This standard, approved by the International Telecommunications Union, describes how multimedia communications occur among terminals, network equipment and services.
H.323 is a widely accepted standard both for communications between the gateway and the public switched telephone network (PSTN) and between the gateway and desktop phones. It is likely to stick around for some time between the gateway and the PSTN, said Raymond Keneipp, service director for network and telecommunications strategy with Burton Group, the research firm based in Midvale, Utah.
But the standard does not provide the kind of rich feature functionality that today's VoIP systems require. As a result, even where it is used between the gateway and the phone, it is overlaid with proprietary information. That means that even when H.323 is used, it does not provide the kind of interoperability between vendors that users have come to expect from standards.
In part, the range of features in VoIP phones makes standardization with true interoperability among vendors hard to achieve, said Jeanne Bayer, director of marketing programs for Alcatel, the Paris-based voice system provider.
"It is hard to standardize in the voice realm," she said. "We have 525 features on one phone and H.323 just supports basic telephony. We have to have something that bridges that."
Nonetheless, H.323 remains the dominant standard in IP gateways today. And it is as close to a uniform standard as there is for VoIP.
MGCP and SIP: Gateway standards
Another established standard is media gateway control protocol (MGCP). It is primarily used between the gateway and the PSTN and is likely to be in use there for some time, Keneipp said.
The protocol that many networking professionals are excited about is session initiation protocol (SIP). SIP has been embraced by Microsoft, and Cisco is moving toward it. The networking giant recently released a phone that can use either its proprietary Skinny protocol or SIP. But this is not yet a standard that allows for interoperability, said Stephen Leaden, president of the Newton, Conn., consultancy Leaden Associates.
Like H.323, SIP does not yet provide the feature richness required by today's and tomorrow's phone systems. So vendors overlay SIP with additional functionality in much the way they do with H.323. That means that while SIP is a standard, it is going to be used differently by each vendor.
The skinny on Cisco's Skinny
Craig Cotton, manager of product marketing for enterprise voice and video with Cisco Systems, said that while the company has its SIP-capable phone on the market, that does not mean that its phones are interoperable with other SIP-based systems or that other SIP-based phones will work with Cisco's VoIP system.
In addition to these multiple standards, there are some proprietary protocols out there as well. Cisco has scrapped H.323 between the gateway and the phone altogether in favor of its own proprietary protocol, Skinny. It has licensed Skinny to a few other vendors who produce Skinny phones. So while Skinny is not closed, access to it is limited to Cisco's partners.
As a result of this standardization stew, VoIP systems generally work best when they come from a single vendor, or a group of companies that have partnered with one another.
That suits Brian Auker, director of technology for the New Brunswick, N.J., public school district. Auker recently installed a Cisco VoIP system. He was able to find wireless VoIP phones to add into the system from a separate vendor that had a licensing agreement with Cisco.
Predictions for the future of standards
Eventually, VoIP will have standards that will allow much more interoperability among vendors. SIP is likely to become the dominant protocol from the gateway to the phone, experts say. And some version of H.323 is likely to be used from the gateway to the PSTN for some time to come.
As standards are ironed out and as SIP becomes more functional, prices are likely to fall for VoIP components. Potential buyers may become more comfortable moving forward with the technology.
But how long with that take?
Zeus Kerravala, vice president of enterprise computing and networking with the Boston research firm the Yankee Group, isn't shy about making a specific prediction. Twenty-four months is his estimate.
Keneipp was not quite so willing to jump in with a timeline but agrees that interoperability is somewhere on the horizon. "We will get to a place where people buy a standard IP telephone that is SIP-based, and they can talk to any call manger and get all the feature functionality," he said. "We are not very far from that."