 Now we are going to go into a little more technical detail with regards to how the overall functionality in NGN is split into different strata or modules or layers or planes Particularly in this module we shall see how the services and transport stratum are defined in NGN what is their rationale and How unique set of functions are split between these two Trying to have no overlap first. Why is there a need for the separation of functionality? If you recall the ISO OSI model The seven layers in there were meant to ensure that a group of similar Functionalities was placed into one layer so that there is no redundancy and There is no Deprivation or I would say there is no dearth of a certain functionality at a certain layer Likewise here also some questions have to be asked and According to those questions some functionality has to be defined and placed into specific stratum The first one is What and whom to deliver That is what content is to be delivered and to whom it should be delivered from whom This is the scope of the services Likewise when we talk about carrying those data packets to execute a certain service we ask Where exactly is the traffic needed to be carried and What mechanism or how should it be delivered? This comes in the scope of the transport stratum Now I've used these two terminologies like the service stratum and the transport stratum Why stratum it is because The concept of layers is already widely recognized as in ISO OSI model and Calling them modules is not feasible because stratum may contain more than one modules So we introduce the term strata as a plural of stratum Let's start with the service stratum The service stratum to begin with is it provides user functions It means the end user Invokes or triggers the functions that would carry the data of that particular user to the call party The service stratum deals with the transfer of Service-related data that is the data that is generated out of the end user to the underlying network The underlying network provides or exposes its Network-related functionality through certain interfaces Now the service stratum uses those interfaces to transfer that data to those network-related service functions Which are underlying The service stratum actually manages the resources associated with provisioning of the service and The interfaces which are exposed by the transport stratum for the service stratum as in network resources the service stratum essentially enables an end user To use a certain application or a service by invoking or activating the underlying network infrastructure The services which are supported by the service stratum are not limited to though include voice video data and all of them combined as in multimedia an Important commentary here is that these services Which are provided by the service stratum? May not necessarily be between two end-to-end users as in the application layer Users that we otherwise know from the ISO OSI layering It could be any entity that invokes a service and any entity that provides a service So it means the services could be between pair entities Now the service stratum actually provides the required Calling and call establishment related functionality between end peers that is also the responsibility of the service stratum Now if we look at the transport stratum, it takes data from the service stratum So essentially what it does is it provides the user function to transfer the data either on the user end that is the originating end host or the terminating end host or The network side it means the network interfaces which would take data from the service stratum are actually related to the transport stratum Now the transport stratum is responsible for controlling and managing the Transport layer resources it means all the aspects which are related to carrying the data over the network Which the data could be either purely user data or the information It could be management related data or it could be control signaling data Any kind of data could be carried by the transport stratum and the responsibility essentially rests with the transport stratum Now the transport stratum invokes or activates part of the transport layer services Either in a static manner if it is a preconfigured set of services and applications or it could be a dynamic provisioning also Now the concept of stratification can be best understood by Appreciating that we have service and transport stratum and within these two We also have the management plane the control plane and the data plane now these planes have their own respective tasks We are going to look at each one of these quickly Now the user plane is responsible. It's also known as the data plane for Handling the data that is generated or received as in voice video or multimedia The control plane is responsible for generating signals Now generating these signals could be for service stratum or for the transport stratum And finally we have the management plane the management plane is responsible for the most important Aspects which are for the well-being and operational viability of the network The management plane is central to the f caps that is fault management the configuration management accounting Performance and security now each one of these management aspects needs considerable time But we'll stop here so that we are able to move on to the functional architecture that still remains to be discussed You