 Now we shall go into a little more detail. The NGN standardization resulted into NGN recommendations. It is also known as the Y series. Compare it to the X series that was regarding the interfaces, the electrical and the network related interfaces. Likewise, we also have the Q series which is related to the signaling. So Y series was all concerned with NGN recommendations. In this module, we shall just start to enter into the main recommendations which the Y series proposes. And then we'd go through one by one each recommendation that needs more attention. Although the recommendation documents are very bulky and you would require a few days to go through all of them. But nonetheless, we'll just skim over these. We'll start with the main recommendations as a whole. Some other recommendations which were not necessarily part of NGN but were required to be as support recommendation documents. And then we'd quickly go through the NGN architecture and the quality of service to begin with. So the main recommendations which come from the ITUTR. The NGN architectures, for instance, which kind of NGN architectures are going to be integrated into the larger next generation network which unifies them all. The end-to-end quality of service. How is it going to be different from non-NGN networks and how the non-NGN networks are going to interface with NGN to provide the end-to-end QS. Security, the generalized mobility. We'll talk about these in due detail. The network control architectures and protocols. Now these are the main recommendations. In addition to the main recommendations, there were some other recommendations. For instance, the Q series. The Q series is regarding signaling. This signaling becomes important because if you recall, we have SS7 that is meant for providing signaling for the telcos. Likewise, when we want to provide the same kind of functionality for voice, viewer IP or IP television kind of networks, we need Q series kind of signaling. This is a bird's eye view, or you may call it the helicopter view of the NGN recommendations across various aspects. You can see that in the left column, we have the ITUTY series with proper nomenclature or the official code which was assigned to it. And on the right, we have the main NGN recommendation groups. These special study groups all emphasize and give recommendations in their own respective domains. Let's start with one by one, each of them. For instance, we'll start with IPTV over NGN. Apparently, IPTV over NGN should be considered an extension to the existing cable TV network. Here, when it is all IP, some new requirements, some functional architecture, some other specifics would arise. All these are addressed here. Then we have the next generation networks because ITUTY is not the only body that calls next generation network as the NGN. There are other organizations like IEEE, the IETF, and for instance, the T-SPAN or the ETSI from Europe. Now, it means different definitions exist. What all definitions actually comprehend and cover NGN as a next generation of networks as such? Then the frameworks and functional architecture models which could be incorporated. In fact, I'll just like to go through them now because we are going to go into their detail in due course of time. Then we have the quality of service and performance. The service aspects, how the services are defined, what are the capabilities of services, and what are the architectures through which services can be provided. For instance, the client-server architecture or the peer-to-peer architecture. The numbering such as the E.164, translation from the telecommunication standard to the IETF standard and vice versa, naming such as DNS and addressing like IP address. The network management like how to manage resources locally and how to configure them remotely. Network control, architectures and protocols understandably how to manage these networks and how to configure them for different environments and for different services. Then the packet-based networks actually addresses, of course, different kinds of networks which support packet-based services all unifying into IP-based. Then security, generalized mobility, carrier-grade open environment. Carrier-grade open environment means that, remember when I talked about liberalization, so carrier-grade open environment means the environment in which the telecom operators all compete to provide services which are recognized as the well-known telecommunication services in an open environment, which is there is no national or state-level restriction as such. Then what is going to be the shape of future networks, going to be like how the cloud computing or the virtualization fit into the context of next-generation networks. And then finally, to certain vice-series recommendations, there are some supplements. Supplements are basically the documents which are always in some add-ons to these respective documents. Coming to the first one, which is the NGN architecture. What is NGN architecture? NGN architecture actually defines the functional requirements for given types of networks. For instance, if the DSL, cable TV network, the public land mobile network or PSTN are to be integrated into an all IP NGN, then what all requirements emerge? Different NGN networks can have different physical topologies, different access networks, which could be NGN compatible or non-NGN. So the functional requirements which NGN architectures address are about all these things. Then we have the end-to-end quality of service. End-to-end quality of service means if there is a link between a caller party and a call party or a client and a server, or let's say two entities which are doing simple chat on an all IP NGN, then how the end-to-end quality can be defined, how can it be ensured? For that, some standardization has to take place. So NGN provides standardized implementation of quality of service in an all IP network. The most important factors for this QoS definition are of course the peak rate, the average rate, the minimum rate, the permissible losses, how the traffic can have some affordable kind of delay, which traffic cannot have any kind of delay, and delay variation which is also the jitter. Once these QoS performance metrics are implemented, then they also need to be monitored. So there is a requirement for standardized performance measurement and monitoring of these entities.