A-IMS aims at VoIP and seamless quality of experience
Five wireless network vendors plus one US CDMA network operator have released details of combined work to update and upgrade specifications for the IMS standard.
The companies — Cisco, Nortel, Qualcomm, Lucent and Motorola — have been pulled together by Verizon Wireless to work on adding specifications to IMS. The group has produced a series of recommendation that it intends to submit for consideration to all the relevant standards bodies, including 3GPP (which initially defined IMS) and ETSI.
It calls the architecture A-IMS, standing for Advances to IMS.
A-IMS addresses several “white spaces”, in the words of Paul Mankiewich, Chief Technology Officer, Lucent Technologies Network Systems Group, which he said “were not as adequately addressed as they should have been.”
Principally, according to Dick Lynch, Verizon Wireless’ CTO, these are around endpoint security, simultaneous support for SIP and non-SIP applications within an IMS environment, peering policy management for users when roaming, management of the quality of the end user experience (particularly for “real time” services such as VoIP), and interaction between SIP and non-SIP applications.
The driver, Lynch said, is the recognition that not all applications will move to SIP, and that there are going to be legacy non-SIP applications, as well as newly developed non-SIP applications, that will not only have to interact with SIP applications, but also work together within a blended service.
No standards schism intended
Those involved were very concerned to point out they are not trying to create a schism in the standards market. Lynch said that other operators and equipment vendors have been aware of the work on A-IMS and have responded positively.
Mankiewich said the work is “clearly complementary – we’ve seen standards not address seamless transactions between one type of access network and another, allowing the same user experience and usage features to move from one technology to another. This technology address the white spaces which were not as adequately addressed as they should have been.”
Motorola’s Fred Wright echoed that view, saying that to date the industry has had to deal with the above areas on an ad-hoc basis because they have not been addressed by the standards.
“The initiative focuses on these things we have to do to build a world class IMS solution.’ Wright said. He added that Motorola would have its first commercial IMS solutions in the Autumn on this year.
There is work going on with ETSI I its TISPAN technical committee to work towards converged fixed and mobile networks. TISPAN’s NGN Relase 1 was released in December 2005, but a second release is currently being worked on, and that will focus on new services and content delivery, with improved security and network management. TISPAn has also held a joint workgroup with OMA, which is also interested in interoperability of services and applications between devices.
ETSI seemed not to know much about A-IMS, but did respond by saying, “As you may be aware, 3GPP currently has a programme of study addressing the evolution of the present 3G architecture and it is therefore an opportune time for the vendor group to bring the A-IMS ideas to 3GPP. The ETSI TISPAN committee works closely with 3GPP and there is an excellent interchange of information between the groups. This is of course very helpful in ensuring full alignment between the 3GPP and ETSI thinking on IMS evolution.
“At the end of the day of course, the success of A-IMS being adopted as part of the evolution of standardised IMS will depend on the other companies participating in 3GPP and/or TISPAN being persuaded of the merits of the A-IMS ideas!”
Qualcomm’s cto, Roberto Padovani, said that by developing policies for different air interfaces, signaling, security and multimedia capabilities, the intention was to” free application developers from the details of IMS and allow them to focus on developing compelling applications.”
Reflecting operator concerns
Consultancy company Ovum produced a note in which it noted that, whatever the outcome of the A-IMS intiative, it highlighted operator concerns about supporting SIP and non-SIP services. Ovum’s analysts Jean-Charles Doineau, Roger Entner and XJ Wang, had the following comments to make.
“Supporting non-SIP-based applications is really the key to ensuring service continuity during the core network evolution. This has not been the focus of IMS specifications so far, which assume in Release 4 that a VoIP move has already happened in the core before moving to IMS in Release 5. As a consequence, the standards consider there to be a de facto approach to service execution, which is agnostically based on SIP, and have often neglected to take into consideration other sorts of traffic, whether IP-based or not.
“Verizon Wireless and its partners have been working on such issues for the past twelve months. One of the main areas in which they have been working is end-to-end mobile VoIP. This aims to provide truly mobile, high-quality voice services that an operator can deploy as a viable replacement for existing cellular voice services, from access to core. A-IMS focuses on optimising voice latencies, whilst at the same time providing the operator with the ability to manage and control the voice traffic using an IMS-compliant service control plane.
“A-IMS also focuses on providing end-to-end security features and management of services for business customers, as well as expanding some fixed services into the mobile market, such as IPTV.
“This work complements the work done in 3GPP and 3GPP2. Both standardisation bodies more or less assume, at least before Release 7, that service providers will operate multimedia combinational services using SIP. These services, combining voice and data in realtime communication flows, can really be seen as the future of telephony. However, surprisingly enough, preparing this move to the future of telephony via the introduction of non-SIP VoIP in the access network has not been considered – leaving open a gap that Verizon Wireless fills with it’s A-IMS framework.”
Timescale for rollout
One thing that is worth noting further is that Dick Lynch said, “It is an inappropriate assumption that we a rerolling out A-IMS. A-IMS is a concept document and there are not tangible deliverables prepared yet. We will begin deploying incremental components of A-IMS within the next 12-18 months. We don’t expect to see A-IMS as a single event but expect it will occur incrementally over the next five years.
What Lynch didn’t say is what Verizon Wireless’ approach would be if A-IMS was not adopted into standards, or survives only in a heavily modified form.
The five pillars of A-IMS
* Bearer Manager (BM): Allocates resources and manages bearer traffic to meet customers’ service quality requirements. The primary functions include policy enforcement, mobility management, security, accounting, and access control.
* Policy Manager (PM): A primary policy decision point for network policies, deciding the ways that the underlying network supports applications on behalf of subscribers and visitors to the network.
* Application Manager (AM): The SIP services platform in the network that authorizes access to SIP services, provides SIP registration and authentication functions, and is responsible for the invocation and management of SIP-based features.
* Security Manager (SM): Responsible for monitoring the network for security threats and responding to them in real time, making decisions on what devices are allowed access to the network based on their posture – a measure of the safety of the device based on the freshness of its software patches and security features.
* Services Data Manager (SDM): The main repository of subscriber and network control data and collects and stores charging data for the network.
Anyone who wants the full A-IMS specification documents can email A-IMS@verizonwireless.com.