The IP Multimedia Subsystem (IMS) is a standard based ALL IP next generation network architecture framework. It enables openness, flexibility, adaptability, functional reusability, policy access and charging controls for the delivery of legacy and innovative services across fixed and mobile access networks that support person-to-person, person-to-machine, and machine-to-machine (M2M) communications.
IMS gives network operators and service providers the ability to control and charge for the traffic and services offered to the end users. Users served by an IMS network are able to access their communication services and applications while roaming as if they were in their home network and from their device of choice. Additionally, IMS encourages a multi-vendor offering of a variety of data products, services and solutions. Network operators and service providers are no longer locked-in with one vendor does all offering. With IMS network operators and service providers have access to a wider set of innovative products while enabling them to place controls on CAPEX and OPEX.
The IMS network architecture defines several functional components that could each be offered in individual nodes or combined in a single network node. The IMS functional components have been defined to serve specific network planes:
- user plane (access control, routing and negotiation of multimedia media streams – voice, video, messaging),
- control plane (routing and control of signaling protocols such as SIP, Diameter to enable the communication set up between the interested parties), and
- services plane (triggering and interworking with network provider and 3rd party applications to deliver innovative communication services)
IMS open interfaces and procedures have been defined and standardizedby respected world organization and standard bodies such as 3GPP, 3GPP2, ITU, IETF, Packet-cable, OMA, and GSMA. The defined standard interfaces and procedures enable:
- the interworking of the IMS functional components within and across network planes,
- deployment of multi-vendor best of breed IMS products and solutions,
- independence from specific network access technology,
- flexible service access by users at any location, at any time, from different devices and client applications
The IMS network infrastructure can be seen as the glue required to support a feature rich and flexible ecosystem that can satisfy present and future communication service requirements based on the strengths and individual capabilities of components and network technologies across domains:
- circuit switch,
- cable and fixed packet data,
- 2G/2.5G/3G/4G LTE and WLAN mobile networks
At the core of the network control plane a set of key functional entities called “Call Session Control Function” (CSCF) have been identified. Four kinds of CSCFs are currently defined:
- Proxy CSCF (P-CSCF)
- Interrogating CSCF (I-CSCF)
- Serving CSCF (S-CSCF)
- Emergency CSCF (E-CSCF)
Some or all of these CSCF functions can be combined in a single network element or can be deployed in individual network elements. The CSCFs are responsible for establishing and controlling multimedia/ single & multi-party communication sessions, ensuring secure and high quality communication, supporting user roaming, service triggering and delivery across different network access technologies, network domains and communication devices.
Northforge’s software engineering consultants have contributed to the enhancements and innovation of world class IMS products that enable communication services and solutions for fixed, WLAN, and 2.5G/3G/4G-LTE mobile networks. The Northforge IMS product development team, working closely with customers, has analyzed, proposed, designed and implemented key software feature optimizations, as well as innovative enhancements, in compliance with the latest 3GPP IMS and IETF SIP standards.