 Let us now look at the functional architecture, that is, the suite of services which are offered as functions to execute important tasks in the domain of IPTV. So this involves essentially all the domains, but we are interested in looking at what exactly is the relationship of IPTV with the engine architecture. So we will start with three functional architectures. And then we are going to look at each of these functional architectures from the functions viewpoint. This will take probably this module and the next because we are interested in going into details in each one of the functional architectures functions. So basically the functional architecture is needed because we need the network functions to provide connectivity, IP address allocation and data delivery. Then we also need service functions. For instance, IP television content to be requested, to be initiated, to be delivered under certain QoS. So all these come under the umbrella of service functions. So primarily three different kinds of functional architectures have been defined and these are most natural. The first one is non-NGN based. When we say non-NGN, it means that any other ITUT or IEEE or 3GPP standard implementation is non-NGN implementation. So if any one of these is used, then the overall engine architecture is not capitalized. So the next one is engine architecture but without the use of IP, multimedia subsystem, the well-known IMS. So that's the second option. And the third option is once we do not have neither of these, in fact we have NGN and we have the IP multimedia subsystem all combined together, which is the best of all. So let's start with the background. So essentially the architecture which is discussed here in detail is NGN based IMS including architecture. And since the overall architecture is going to be such that it has to be backward compatible, so it is also generalizable for non-IMS based NGN IPTV services. So the IMS services in the case of non-IMS based NGN services is provided through something known as control functional block. Now these are the modules which are proprietary, which are provided by different technologies. For instance, as I mentioned earlier, IEEE based standard 3GPP and ITUT, etc., ITF, etc. So you choose either of them as long as it is not IMS based, it is going to make use of some functionality and that is what is addressed here as the control functional block. So it means that if you want to provide IPTV services, those IPTV services will have to be provided essentially through some way and those are the possible control functional blocks which are integrated in this generalized architecture. So the well-known modules in the NGN like network attachment and control function and the resource and admission control function, now these functionalities actually are provided by the same functional blocks for authentication, address allocation, resource control, etc. So it means that this architecture, the one that you are seeing right now is quite flexible, which is going to cater for NGN based non-IMS IP functional services as well. For now, let's look at it one by one. So we have the NGN architecture in the middle, we can see the service stratum, we have the transport stratum. Then on the left hand side, we have the end user functions. On the right hand side, we have the management functions and the IPTV content provider functions. Now a lot of functions within this overall figure and even when they're within the NGN architecture, we have the application functions, we have the service support functions and the service control functions and here you see the IMS here and then we have content delivery function and then we have the transport function as well under the transport stratum. So it means we have got a lot of functions, all these functions can be grouped together. So the headings that you see here are actually the functional groups which you can say have associated set of services. So let's start with the end user functions. So the end user function is actually the place from where special content request is initiated for IPTV. So it can be divided into two functional groups. One is the IPTV terminal function that is the user equipment functions and then the home network function that is how the user equipment is going to be connected through some kind of gateway mechanism with the NGN based IMS IPTV architecture. So as far as the IPTV terminal functions are concerned, these are typical device based functions which include taking the user click or user URL request. So it means a user clicks, it means it would be a control command, the system or the end terminal equipment is going to take that command and it is going to interact with the application depending upon what particular command the user has given. So it is also going to involve obtaining the service information, for instance, which programs are being offered at the moment. Then certain kind of encryption decryption and encoding decoding is also required. And then once a user makes a request, a reply comes back. So that reply is then decoded and finally displayed. So end user functions are very important. The home network functions are essentially related to networking. So having connectivity between home network and external network and including all the required services, for example, address allocation, if that is being implemented and if the forwarding has to be done based on IP routing information, then we have the application functions. Now the application functions actually sit on the farthest end. It means the user now from the ITF has the capability to choose certain content. Now this content is there. So it means the application functions would provide the user with the capability to select and purchase the content. Of course, this content will have to be provided to authenticated users and its execution is all dependent upon if the user has the subscription, which is available. So it uses user profiles and metadata. For instance, user settings, what are going to be the global settings in terms of time zones, the language settings, typical linear TV settings, the video and demand settings. If a user is interested in personal video recording, then PVR settings and then a certain a service action data, that is, if a user has carried out some action associated to certain service, it generates some data, but that data has to be recorded as well at the application. For instance, if a user pauses the video in the middle of say watching movie, then it needs to be bookmarked so that a user can later retrieve it. Likewise, recording the contents by the user actually has to be done in a methodical way. So a list has to be maintained in what exactly a user is recording. So it means the application functions are also going to be related to the content creation, content preparation, its encryption, decryption mechanisms and its overall protection so that non-authorized users do not view it.