IP Multimedia Subsystem (IMS)

The Internet Protocol Multimedia Subsystem or IP Multimedia Subsystem (IMS) was develop the 3G.IP industry in 1999. It was initially an architectural framework. It was later presented to 3rd generation partnership project( 3GPPP). During the 3G era IMS was about multimedia applications rather than that of telephony. Earlier it was not planned to be a mobile networking application, but today the architectural framework has become standardized across the industry for next-generation mobile networks.

How is IMS Architectural Made?

Mainly 3 layers makes IMS Architectural framework these are- service/application, control and transport layer. So these layers give functions to manage mobile networks.

  • Service/application layer– in service layer it hosts and executes the service for the users.
  • control layer– This layer is responsible for session controlling and management. The control layer regulates the traffic between the transport layer and the service/Application layer by authenticating and distributing traffic.
  • transport layer– This layer is responsible for supporting the architecture’s core network by acting as a gateway linking access layers and IP networks.

Elements of IMS Core

1- P-CSCF – Proxy Call/Session Control Function

The P-CSCF provides the central entry point into the operator network. All requests need to go through the P-CSCF and that entity should be located close to the connecting endpoint. This is to increase network efficiency by avoiding useless traffic transport and reducing latency.

2- I-CSCF – Interrogating-Call/ Session Control Function

The Interrogating-CSCF (I-CSCF) queries the Home Subscriber Server (HSS) and based on its response routes the message to the correct S-CSCF. If no S-CSCF is indicate by the HSS, the I-CSCF will select S-CSCF.

3- S-CSCF – the Serving Call/Session Control Function

The Serving-CSCF is the worker in the IMS world. It communicates with the HSS using Diameter (Cx-interface) to retrieve information about authentication and in order to retrieve user profiles for triggering different application servers. 

4 – Emergency Services Implementation (incl. E-CSCF)

The P/I/S-CSCF implementations have extend to identify emergency registrations. In case of such a registration, the I-CSCF will add an emergency flag in the Diameter User-Auth-Request so that the HSS will ignore roaming restrictions. 

The signaling protocol that is commonly use to communicate is Session Initiation Protocol (SIP). SIP is use for managing, maintaining, routing as well as authorizing and terminating real-time sessions. To put it in simple terms, Session Initiation Protocol (SIP) signals and controls the multimedia communication sessions.

What Makes it Unique?

Smallest container sizes: Based on microservices and fully containerized using Kubernetes, our container size of less than 25 MB allows for rapid service delivery, also extending the capacity of your platform. 

Platform-agnostic: Born in the cloud, our IMS runs on any public, private (bare metal) or hybrid cloud environments, and off-the-shelf hardware.

Minimal resource footprint: The most efficient use of hardware resources thanks to cloud-native architecture, which is very small container size and modular approach.

Flexible Business model: Our business model based on the number of subscribers requires a low upfront commitment, reducing our customer’s overall capital expenditure.