 Let us now look at how the services can be provisioned particularly the real-time multimedia services in IP multimedia subsystem based environments in NGNs. For that we will have to look at the traditional view, how IMS creates a horizontal view and what are the services which can be invoked from the IMS system. So once we say that we have NGN architecture with its complete set of services and functionalities, we are actually looking at the service provisioning from the horizontal view point that is. We are interested in using the underlying infrastructure coming from the transport stratum and the service stratum on top of that to actually use the services in a very repeatable manner without having to create functional requirements and services for individual user applications. For that horizontal architecture in NGNs actually implies that the services would be facilitated through service enablers which would be the common functions reusable and repeatable for a multitude of applications. Now this is actually a move away from the traditional view point which is known as the vertical implementation of services. Vertical implementation implies every new application comes with its own dedicated suite of services. So let's look at the vertical view with regards to the traditional services. So if each service has to be provisioned and that there is some kind of network agnosticism or an assumption that the network wouldn't provide us the services, we have to cater for each and every service and functionality at our own. In that case the vertical implementation would require services ranging from authentication, authorization, charging down to the routing and service provisioning requirements. So it means that traditional view would require a lot of duplication and repetition of certain services. But this is not what is desirable for that IMS comes into play. So IMS actually makes use of the effective and efficient implementations at the service and transport stratum to utilize and invoke common sets of services. It means that IMS actually would now be a set of common services which are not specifically designed for a specific or a singular service. So the consequences with that already available common sets of functions and services, whenever a new service would be deployed, it would result into some kind of efficient, short and immediate deployment. So we say that the time to market and the customer delivery would be improved. And then the overall service creation and service delivery would be facilitated and simplified to a great deal. And this actually means that in all the service providers, the NGN operators and the customer premises equipment providers would all have lower capital expenditures and lower operational expenses. So let's summarize what do we mean by the horizontal functional architecture for IMS in order to provide real time multimedia services. As you can see, we have the service stratum. The service stratum actually has the support functions like application support and service support, which are actually now connecting to the IP multimedia subsystem IMS using certain functional entities. These functional entities are the user profile, media resource control, media gateway, breakout gateway, the serving and the proxy call session control functions. So in all, the point that we need to understand from this whole diagram is that the functions are being reused for any service with or any application which is utilizing the NGN architecture with IMS as the service platform. So you see here the beauty about this IMS is it is once deployed and it can be repeatedly used for other applications and user services.