 Let's look at a specific service which we call as the internet protocol-based television, IPTV. So if it is provided through IMS, then what are the services which IPTV could get from IMS that it does not otherwise get from pure IP-based network with no infrastructure support for service provisioning. So let's look at the types first and then we are going to look at the control functions which are provided to the IPTV. So IPTV basically is a service that has been very favorite to all of us. We've been watching live and streamed and sometimes stored content on internet. So if this television service was always there, that we call as the non-NGN IPTV, which was traditionally the IPTV over the internet service provided internet. After the coming of NGN, then this IPTV actually came in two more variants, that is a non-IMS-based IPTV and IMS-based IPTV. Now this NGN-based IPTV is actually an extension which is very natural because NGN had to replace existing networks as an integrated service delivery platform. So the non-IMS-based NGN basically is a step towards the final goal where the IPTV is all provided by the IMS-based services. So the IMS actually is responsible for providing certain services to IPTV. First one is access. For that, there is a protocol which is an extension protocol to radius. We will talk about it as the AAA service protocol. So basically, a diameter is provided as IMS service to IPTV. It allows communication to take place between the application function or the API with the database that stores the application profile because each application has its own QoS requirements. So these are consulted and tallied through the database. Then the application function also interacts with the user service profile. That is the user is entitled to which kinds of services. Now this information of user is specifically available in home subscribers station. Another protocol or service which is provided by IMS for IPTV is the session initiation protocol service. This is related to signaling and call control for multimedia, especially in this case of IPTV. So it actually manages the interaction between the service control function in IMS and the application function. And then it also involves the interaction between the service control function and the content delivery functions which are invoked at the servers which are going to provide the content. We are now going to look at the complete picture of the functional architecture for IPTV which is based on IMS. Now here you see different kinds of variants which are possible. For instance, if the IPTV application function is not utilizing the service control function and content delivery functions and if it is not based on IMS, then it is basically a non IMS based NGN service. But if it is using IMS as the underlying service where the service control function is present and if it is also interacting with the content delivery function, then we say that it is IMS based NGN IPTV. So you see here that different kinds of interactions are being shown in here where the IPTV application functions in the core of the network is now interacting with the end user API. And on behalf of the end user API, it is interacting with the underlying IMS core.