SIP is no guarantee of interoperability

Session Initiation Protocol is generally held to be the dominant VoIP standard. Yet interoperability between different vendors' SIP systems remains a challenge because the standard is immature, say analysts from Yankee Group and Forrester Research.

Vendors continue to make a big deal about Session Initiation Protocol (SIP) compliance and opening up their APIs to partners and rivals, but using an open, standards-based unified communications architecture is no guarantee of interoperability. Enterprises are finding that it's still not very easy to get things to work together. Even simple VoIP interoperability is tough to achieve.

"Even integrating Microsoft and Cisco is extremely frustrating," said Zeus Kerravala, distinguished research fellow at Yankee Group.

He pointed out that Cisco and Microsoft have built a specific application called Cisco UC Integration for Microsoft Office Communicator (CUCIMOC) to integrate the two vendors' unified communication architectures. "If interoperability works so well, why'd they have to go and build a custom integration to make them work together?" Kerravala said. "If the market leaders can't interoperate easily with each other, you're never going to be able to introduce a small vendor into your environment."

SIP: Not yet mature enough

Everyone talks about SIP compliance in their open, standards-based unified communications architecture, but each vendor implements its own version of SIP. The problem, some experts say, is that SIP needs a little more time baking in the oven.

"Even if you follow the standard, SIP isn't very tight," Kerravala said. "There's still room for interpretation, and you can be non-interoperable even if you are standards-based."

Also, the number of features standardized by SIP isn't that long, he said. Consequently, vendors who want full-featured unified communications architecture have to create extensions to SIP. They remain in SIP compliance when they do this, but the extensions to SIP make their technology proprietary.

"So if a vendor wants to come out with a full-featured phone system, they don't have any option except to modify the SIP standards to have those features," Kerravala said. "Then, by definition, you are no longer standards-based. The looseness of the standard leaves it open to interpretation, and combined with the lack of features, it's a big problem."

Don't demand SIP compliance, demand interoperability

As noted above, SIP compliance won't guarantee a unified communications architecture that is interoperable with other vendors. And SIP isn't the only standard that vendors use when building their products.

"SIP is a core anchor protocol, and it's important that we consider it. But if you really think about it, [unified communications] is a multi-protocol environment where they're using multiple protocols for greater functionality and features," said Elizabeth Herrell, vice president and principal analyst at Forrester Research.

Herrell said enterprises will get true interoperability only by explicitly demanding it and by channeling their budget dollars to those who deliver.

"I think companies have to demand that they want openness," she said. "Demand openness by purchasing [from] the vendors that provide openness today. I think companies will demand change by buying the more open products, and other vendors will see it's no longer competitive to work in a fully proprietary world."

Other vendors may be pushed to interoperate because of the heterogeneity of enterprise environments and the desire to have best-of-breed collaboration and communications. "Most companies have already made a commitment to IBM or Microsoft for email…. And they have made a phone decision with Cisco or Avaya and are not going to walk away from those platforms," Herrell said. "What they have to do is work with both vendors. Companies are not willing to rip and replace to standardize on a single vendor when there is not an incentive to do so."

Lack of open, standards-based unified communications stifles adoption and innovation

The lack of interoperability has caused enterprises to react in a variety of ways. Some have tried to go the multivendor route, relying on vendors to come in and tie together APIs. This is not pain free, O'Berry said.

"If you're out there and work with companies that have established 50-50 partnerships [with other vendors], then you have all these ninja monkey engineers running at you from all these different companies, and we get overwhelmed on the customer side," he said.

Kerravala said some customers are simply holding back their dollars while waiting for the interoperability picture to improve. Others are biting the bullet and going with a single-vendor solution, but that doesn't help if an enterprise turns around and acquires or merges with another company that uses a different vendor. Then the enterprise is faced with the interoperability problem all over again.

A lack of interoperability also stifles innovation, O'Berry said. Big vendors might solve problems on a case-by-case basis by tying their APIs with partners, but smaller companies are vulnerable to being left out in the cold.

"I think it's a huge problem for the industry," Kerravala said. "I don't think vendors understand how interoperability and open, standards-based products drive adoption up. You might not get a bigger piece of the [pie] with standards-based products, but the pie is going to be much bigger."

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