About the components
Our IMS testbed architecture is depicted in the figure. The core of our IMS system is based on the Open Source IMS core of OpenIMS found at http://www.openimscore.org/.
One key characteristic of the testbed is that, its deployment is "cloud like". This allows us from the administrative perspective to easily hand over the testbed for experimentation and bring it back to its initial state. Thus, even if an experimenter gets root access to the services, we can easily reset the state and the configuration of the testbed. In future this will allow us to take a snapshot of an experiment and re-execute it or continue from its latest state.
OSIMS consists of the following services/components:
Home Subscribe Server (HSS)
The Home Subscriber Server (HSS) , which contains the subscription-related information, performs authentication and authorization of the user, and provides user's physical location information. In short acts as a Master database.
A Serving-CSCF (S-CSCF) is the central node of the signaling plane. It is a SIP server, which also performs session control
A Proxy-CSCF (P-CSCF) is a SIP proxy that is the first point of contact for the IMS terminal. Assigned to an IMS terminal during the registration, and does not change during the duration of the registration
An I-CSCF (Interrogating-CSCF) is a SIP proxy, which provides a service locator function. Acts as a Topology Hiding Internetwork Gateway: A case of I-CSCF, which hides the configuration, capacity, and topology of the network from the outside.
This service, provided by OpenSIPS, enables IMS clients to be aware of other accounts presence. The experimenter configure this via the OpenSIPS server
OpenSIPS (Open SIP Server) is a mature Open Source implementation of a SIP server. OpenSIPS is deployed on OSIMS as a customizable routing engine, but also for its capabilities: unifies voice, video, IM and presence services.
A streaming media server. It hosts a service with IMS accounts mapped to streams, in order to experiment with media on IMS clients
All the hosting machines are connected to an OpenFlow switch (OpenVSwitch). This enables the experimenter to perform QA actions
XDMS as specified by the Open Mobile Alliance (OMA) is to manage groups, contact lists and access lists.
The well know VOIP server, deployed to enable more scenarios.
WebRTC2SIP gateway service
A WebRTC2SIP gateway service is deployed in OSIMS together with the core. It enables the connection of any HTML5/WebRTC SIP client using WebSocket as transport or running on the browser to a SIP/IMS server.
The UCT policy framework is installed in OSIMS, so experimenters can also deploy and apply own policies.