 In this module, we are going to appreciate if there is a distinction between services and applications with regards to the next generation networks. For that, we'd have to clearly define each one of these and see how NGIN considers them as their definition and then how makes necessary arrangements for their provisioning. The applications as such, if we look at the classical perspective, have existed for a fairly long time now. For instance, we know of the worldwide web browsing that is web service. It is a client-server application. Likewise, we can think about any other peer-to-peer application as well. Now what makes it qualify as an application and not as a service? The first one is that the communication that takes place between the client and the server, it does not require any specific signaling. If there is a connectivity requirement between client and server, that is already catered for using the DNS framework, the IP addressing, and the server availability on the port. NGIN recognizes this as a reality and provides applications from the NGIN portal or NGIN perspective. If you look at the services, services are distinct from applications, from the classical understanding. That is, services require the presence of some underlying infrastructure for call and session control. It means that there's a requirement for a service to be executed in that a certain call management system like dialing, call acceptance, acknowledgement mechanism should exist. From that perspective, it is different from application. The quality of service-based voice over IP is one good example of a service. We call it, you can call it a voice service. Now this voice service is actually requiring some kind of signaling. Session initiation protocol is a signaling framework that implements all the call handling features on behalf of the QoS voice enabled voice over IP service. NGIN also recognizes this as a reality and NGIN makes necessary arrangements to ensure that whether it's a service like this or an application that we have just seen are seamlessly provided over the NGIN network. Let's look at the overall services and applications from the network point of view. Here we see that we have the top layer that comprises services and applications. Now the applications wouldn't require much of an underlying infrastructure with regards to call signaling. The services would require, as you can see, we have independent application server and we have a service database. You might have observed that when it comes to application, we have a server providing the services. But the service database actually means all the services which we have seen requiring some kind of underlying infrastructure are put in a database because these services are called by the end users. Then we have users, user database, which we are not going to go into much detail about. And then we have the underlying layer also called the control layer. Control layer is meant to provide the required signaling for the services on the services layer. Then we have the core layer and we have the access layer. Regarding the core layer, we can see that it is a connectivity of routers. Now these routers can be directly connected to each other through IP or there could also be provisioning of MPLS, the multi-protocol label switched based IP network configuration that allows a faster processing of the IP packets using the MPLS domain concept. In the access side, we have individual networks. For instance, it could be a PSTN or the ISDN network. It could be a fixed network or a broadband mobile network. Using these independent networks with the core requires some kind of help from the underlying signaling network and the media gateway network. The signaling network provides all the physical layer signals which are required to establish a call for the control layer that we have seen in the control nodes you can see. Now the control part that we have just seen in NGN is recognized as one of the most important entities in the NGN overall framework. And for that, the 3GPP standard as in release 8 has been adopted as the IP multimedia subsystem, the IMS, as the control nodes in the control part of the NGN. The ITUT recognizes this IP multimedia subsystem to be part of the NGN recommendations. And it is used for services which require the underlying underlying architecture for control signaling, such as the voice over IP if it is QS-based in particular.