 Now we are going to look at the last functional entity in detail with respect to different underlying networks which it supports. The transport resource control functional entity that at the end of the day manages QS control, whichever QS policy is coming right from the service control function. So we look at its role and then we look at the operation under different network type settings. So we all know that NGN is pretty much access independent. So the access technologies can vary. They are all interoperable in an integrated NGN architecture. They can coexist as such there is no problem. But when we are talking about providing quality of service and the quality of service control, the role of the transport resource control functional entity becomes very important. It is one of the functional entities in the resource and admission control functions. It is dependent upon the underlying technology because each technology has its own peculiar behavior, its own protocol design and its own definition of the parameters. So for different networks such as the IP networks and if the multi-protocol label switching is enabled, IP, MPLS networks, pure Ethernet network as Layer 2 technology and broadband and wireless mobile networks including both YMAX and the LTE and LTEA. So this TRCFE is going to have a very important role in assessing the attributes, the features, the protocols of the access technologies. So when we are talking about admission control, admission control is dependent upon the availability of existing resources in the network and the requirement which is coming in a certain QoS request for a flow, particularly for media flow. So to understand the current state of the network, there is something known as the management for performance measurement. We will talk about it later but just consider it for now. It is again a function that is used to assess the current state of network parameters in order to make sure that QoS requirements are amicably met. So this MPM is used by the TRCFE to admit the service requests depending upon the QoS profiles on the basis of the existing network performance. The existing network performance is measured through collecting certain logs or information. For instance, the bandwidth availability, the current measured QoS parameters such as latency, delay variation or jitter, packet loss ratio, etc. So admission control by TRCFE is dependent upon the information it gets from the management for performance measurement module. So if we are talking about different underlying access technologies, we can start with IP. So this TRCFE is very useful in interacting with IP because IP routing is implemented on routers through different routing protocols such as RIP, OSPF, etc. So the routers can implement quality of service using the ITF recommended diff serve architecture which is based primarily on packet classification and differentiation and admission control. The packet differentiation is done either in IP version 4 or IP version 6 depending upon what is the available header information available. In IP version 4 it is the QoS classes and in IP version 6 it is the traffic class field. So essentially both of these come under the DS differentiated services field. The other important attribute of the diff serve architecture is the admission control. Since we are talking about the RACF, the resource and admission control function. So this TRCFE manages the links or all the interfaces in our router and then correspondingly it performs link by link resource management and the allocation of resources. Now this is essentially meaning buffer management and admitting a certain flow or denying a certain flow at the input of a router. So admission control is another important functionality carried out by the TRCFE for IP. Since we are talking about NGN networks with very high speed requirements, so the multi protocol label switching is something that makes the processing of IP packets very fast. And it does so by introducing a header known as the shim header between layer 2 and layer 3 known as a label. Now this label is used in processing the IP packet as it moves from a router to another router known as the MPLS domain. So the paths in an MPLS domain are known as the label switched paths which are pre provisioned for a certain flow. For instance avoid flow or IPTV flow. So correspondingly this MPLS domain results into a virtual MPLS transport network that is it exists on top of an IP network but since it is using labels so it is virtually existing. Now these labels can be either assigned in the form of a preset forwarding table or a certain real time signaling protocol such as resource reservation protocol traffic engineering can be used or constrained label distribution protocol can be used. So whatever is used MPLS uses essentially a stack of labels such that the top of the stack is a processed in the form of the last in first out manner. So a QS route is basically a label stack which comprises a concatenated label switched paths or a series of routers which are connected in a single path. Then we have the wireless fixed and mobile broadband. We have the examples of YMAX and LTE, LTEA. Here again the QS control is handled through the radio interface which is led to the QS signaling for QS control is done in the radio part. And we already know certain QS classes which were defined by the ITUT, ITF and the NGN community. So for these QS classes in wireless the transport resource control functional element, functional entity can actually carry out some kind of priority based scheduling at the base stations. It could be a base station in LTE, it could be a base station in YMAX. And in addition to that this TRC FE can also carry out some kind of runtime adaptive bandwidth allocation known as the dynamic bandwidth allocation. So in all finally we can say that the TRC FE is dependent upon the underlying technology and corresponding to that technology it changes its QS control with whatever features are available in that technology.