Industry observers who thought the IP multimedia subsystem concept was the latest in a long line of well-intended but generally convoluted technology standards can now size up Advances to IMS (A-IMS), an evolutionary reference document compiled over the last year by Verizon Wireless and several of its vendor partners.

A-IMS was announced in a press conference this morning by Dick Lynch, chief technology officer of Verizon Wireless, along with executives from suppliers Lucent Technologies, Cisco Systems, Motorola, Nortel Networks and Qualcomm. The document proposes architectural enhancements to the existing IMS standard, Lynch said. Most notable among those enhancements is proposed support for both SIP-based and non-SIP-based traffic types in an IMS environment, a significant industry acknowledgement that not all applications will be become SIP-based anytime soon.

“This is really an architectural vision of where we believe IMS needs to go,” Lynch said.

Verizon Wireless and its vendor team plan to pitch the A-IMS architecture to 3GPP and other standards groups as a potential addendum to existing standards. The architecture and the 300-page reference document that describes it have been in gestation for about two years, the first of which Verizon Wireless spent studying some of the gaps it felt existed in the original IMS standard. During the last year, Verizon Wireless drew technologists from its vendor partners to attack those gaps and develop solutions.

Ed Salas, vice president of network strategy and planning at Verizon Wireless, said, “We created more questions for ourselves than answers. We think IMS is great. We just saw some gaps in the standard."

Fred Wright, senior vice president of networks and enterprise for the North America region at Motorola, added, “We were addressing the white spaces that weren’t addressed as they should have been in the standard, and we’re adding context.”

One of the biggest of those white spaces was the lack of support for non-SIP-based applications and products. "IMS is of course built around SIP, but we have a lot of non-SIP applications and products that don’t fit into the model," Salas said.

Peter Clarke, director of business development at Cisco's Service Provider Routing Technology Group, said vendors saw similar concerns about IMS at the same time Verizon Wireless was asking it’s own questions. “We were asking the same practical questions,” he said. “We had some concerns about IMS being too focused on SIP.”

The A-IMS document includes advances pertaining to uniform support for both SIP-based and non-SIP traffic types, but also other enhancements. A multi-tiered service interaction management feature allows for the application interactions of both SIP and non-SIP services to take the state of the network into account. Also, Salas said the architecture better support fully mobile VoIP over CDMA 1X EV-DO networks--the technology Verizon Wireless currently has in place. "SIP has to be optimized to reduce latency to support that," he said.

Ovum analysts put out a statement this morning observing that A-IMS goes along with the current thinking about IMS that the standards offer useful elements that carriers and vendors can choose to build upon. "Regardless of how this will play out in the next couple of years, by supporting both SIP and non-SIP applications, A-IMS focuses on seamless service migration during the evolution of the core network architecture," statement from Ovum said. "It represents a very good example of what could be expected from carriers wishing to move to VoIP using an IMS-compliant evolutionary path."

Among other enhancements in the document, the addition of a security manager and extension of security agent capabilities to all network devices. In addition, it calls for a bearer manager element that provides two IP addresses for a mobile terminal, one in the home network and one in the visiting network. This dual anchoring concept allows latency-sensitive application to use the visited anchor, while other applications requiring service provider control use the home anchor.

A bearer manager would be a new IMS network element, but Salas said it would actually consolidate the functions of a home subscriber system and other elements. "We're looking at a more organized and operator-friendly approach to IMS," he said. Another suggested adjustment is the establishment of policy servers in both home and visited networks to allow for more seamless three-layer peering according to the home network's policies.

Cisco’s Clarke said the partnership approach that Verizon Wireless took with the A-IMS project is emblematic of new ways in which carriers and their vendors are working together. "It's a group of people who haven't work together in this way before," he said. However, other vendors downplayed that notion.

“It’s not uncommon at all,” said John Marinho, vice president of corporate strategy at Lucent Technologies. “It’s all part of the standards process.”

As A-IMS progresses in the standards arena, Verizon Wireless plans to begin trials of the architecture. Lynch offer that the carrier’s deployment could occur within the next 12 to 18 months, though it could be between one and five years before A-IMS gains broad industry adoption.

Salas said, “It’s something that if Verizon Wireless is the only carrier to put A-IMS in its network, then it’s worthless. It’s intended to benefit the whole industry.”