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A-IMS (Advances to IMS) Aiming to be the New
IMS Blueprint

By Ronald Gruia            October 2006, Volume 1/Number 5

IMS Magazine

The proposal of Verizon Wireless (News - Alert) and the five network equipment vendors promises mobile carriers more flexibility in managing applications subject to certain QoS (Quality of Service) constraints, and in handling mobility, security, accounting functions and PFO (Packet Flow Optimization). Security is a major focus area, with the objective to allow service providers to administer and enforce their own security policies. The idea is to protect the network at the edge, by ensuring that endpoints attempting to gain access are If you ever took a look at a full-blown IMS diagram and were challenged to remember the acronyms of all the functional boxes, then get ready for the next challenge of A-IMS, or Advances to IMS. A-IMS can be most simply thought of as an add-on to the original IMS reference architecture, and it represents a joint effort of core infrastructure vendors such as Cisco, Lucent, Motorola (News - Alert) , Nortel (News - Alert) and Qualcomm (News - Alert) along with Verizon Wireless. These players announced at the end of July 2006 the completion of their two-year joint project, summarizing their conclusions in a document that proposes a variety of improvements to the original IMS specification. compatible with the security policy before they are admitted to do so. Other improvements include the ability to handle interactions between SIP and non-SIP apps in the same architecture, in addition to provisions for enhanced policy controls.

A Deeper Look at A-IMS The A-IMS
essentially presents five extra network elements beyond the original IMS specification. Each of these new elements has numerous functions, which both overlap and augment the existing IMS features, as follows:

1. Application Manager (AM) — sanctions access to various services within the network and manages SIP-based features. The AM is very much analogous to the three CSCF functions (P-CSCF, S-CSCF and I-CSCF; i.e., the proxy, serving and interrogating functions) and PSTN routing (BGCF — Breakout Gateway Control Function) (News - Alert) specified in the 3GPP IMS framework.

2. Bearer Manager (BM) — presents a wireless endpoint (i.e., a cell phone or PDA) with a couple of IP addresses: one to be used to control that device in the home network and the other for roaming partner networks. The operator can use these IP addresses to establish who is in charge of handling and supporting the service (the operator itself, the MVNO, or other partner service provider). Other BM functions include QoS management, accounting, security, mobility and access policies and PFO.

3. Policy Manager (PM) — delivers uniform policy enforcement within the home network and in roaming partner networks. The PM controls the behavior of service running on the network depending on its underlying conditions. This enables carriers to effectively manage the way the network supports the applications running on it. The PM also provides uniform support for both SIP-based and non-SIP based applications, and this is an enhancement of the original 3GPP specs, which were solely devoted to the support of SIP services. Like the BM, the PM also manages QoS, accounting and mobility / access policies.

4. Security Manager (SM) — changes various network security parameters depending on the reigning network traffic conditions and requests made for access and services. In other words, after an end-user authenticates for priority network access, the SM is in charge of updating the impacted network elements and, if necessary, call up extra security parameters. The SM also monitors all network activity by performing a correlation analysis according to certain baseline usage patterns. Hence, it is able to detect any abnormalities and invoke other network elements as part of a response to a threat.

5. Services Data Manager (SDM)
— can be thought of as the HSS (Home Subscriber Server) element from the original 3GPP IMS spec. The SDM is a big centralized database that stores all the subscriber, network control and accounting (charging) information for the entire network. The difference in A-IMS is that the SDM is also the data warehouse for both SIP and non-SIP services.

Parallel Developments in Standardization
The standardization of IMS is still very much a work in progress, despite the more than 50 functions and 30 interfaces already defined. Obviously, the players behind A-IMS are presenting their proposal as an add-on to the already existing IMS specifications, since they are keenly aware of the multiple ongoing deployments around the globe for both wireline and wireless operators. They maintain that their improvements can work as an overlay to the existing implementations without the necessity to rip and replace the new IMS gear with even newer A-IMS equipment.

The Verizon Wireless initiative is tackling some of the same MMD (Multi Media Domain) issues that 3GPP2 is attempting to solve. 3GPP2, a sister organization to the 3GPP, focuses mainly on CDMA and MMD domain standards and practices. The issues that 3GPP2 is working on include QoS negotiation, AAA (Authentication, Authorization and Accounting), improvements for network independence, session handoff, VoIP, traditional voice services and Internet access services. However, there are some planned A-IMS improvements that are targeted to be above and beyond the existing IMS/MMD standards and, as such, the group will likely be submitting this initiative to both the 3GPP, 3GPP2 and others for adoption.

Besides the 3GPP2 effort, TISPAN (Telecommunications and Internet Converged Services and Protocols and for Advanced Networks) is concentrating on the interactions and requirements to support non-SIP applications. TISPAN is a subgroup within with the ETSI (European Telecommunications Standards Institute) that works very closely with the 3GPP, and is evolving existing (non-SIP based) services onto next-generation infrastructure.

While Verizon Wireless is a member of 3GPP2 via its relationship with TIA, the vendors the operator works with are all members of both 3GPP and ETSI. Thus, there’s a good chance that the A-IMS changes could be introduced initially via the 3GPP2 and subsequently by 3GPP and ETSI.

Key Takeaways
One lingering question after the public introduction of A-IMS was, why not pursue the introduction of the changes via the already existing standardization bodies rather than as an independent, standalone project, which would then be pitched to these organizations? Historically, Verizon and Verizon Wireless have always opted to develop infrastructure and technology either in-house or refine it by working closely with vendors, rather than buying it outright from the vendors, and the A-IMS initiative certainly fits this pattern. While the improvements being proposed are for the Verizon Wireless CDMA2000 1xEV-DO network, they can be relevant to other network technologies as well, due to the “access agnostic” characteristic of the presented proposals.

However, another observation is that only five of the “big-10” group of major network equipment vendors are a part of this initiative. Noticeably absent from the A-IMS effort are Ericsson (News - Alert) , NEC (News - Alert) and the newly-formed Nokia (News - Alert) / Siemens (News - Alert) JV. Ericsson and Nokia were two major champions and IMS pioneers, making innumerous contributions to the original 3GPP specification. Could this be an attempt by the North American vendors to shift the “IMS center of gravity” back towards their region? Certainly, they needed some catching up in terms of mindshare and why not leverage their CDMA strength to further enhance IMS while addressing some key concerns of a Tier 1 regional wireless operator?

Another takeaway is the evolutionary nature of A-IMS, which is certainly important in the modus operandi of today’s carriers. Most of the service providers across the globe have been pragmatically asking for a more gradual migration to next-generation infrastructures. A-IMS supports both SIP and non-SIP applications and focuses on a seamless service migration as the core network architecture evolves. Therefore, the IMS sales pitch can be greatly enhanced by blending new IMS applications with existing services. As Metcalfe points out, the value of a network is proportional to the square of the number of users in that network.

Finally, another implication of A-IMS is related to the notion of walled gardens and “net neutrality”. While A-IMS does provide substantial security, network management and business policy enforcement functions, these very same enhancements can be used as a mechanism to empower operators to follow, manage and charge other service provider applications running in the Internet domain. The temptation will certainly be there for these operators to use some functionality provided by A-IMS for their own purposes, including even directing end-users to their company’s applications, should these end-users attempt to access a similar application from another provider. There are several features in A-IMS that can allow an operator to control the network according to their interests (for instance, by tweaking the QoS via the SM, so that services of alternative operators would run in sub-optimal conditions, or by charging those alternative operators an extra fee for enhanced QoS, via the charging functions of the SDM and the packet accounting functions of the PM).

However, while some of these controls (such as tiered pricing based on QoS) could be justified, the “walled garden” approach would certainly contradict the original vision of IMS as a truly integrated network architecture capable of delivering benefits for all carriers and end-users. Therefore, the true value of A-IMS will also be dictated by what the service provider chooses to do with this technology — for instance, an operator opting to downgrade or even limit applications that end users find useful could be potentially committing a big strategic blunder.

Ronald Gruia is Program Leader and Senior Strategic Analyst at Frost & Sullivan covering Emerging Communications Solutions. For more information, please visit www.frost.com. (news - alerts)


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