 So far, we have looked at the transport aspect of the transport stratum functions. Since this traffic which is transported has to be managed and controlled, the control functions are the essential aspect of the transport stratum. So in this module, we should look at the transport stratum functions with respect to the control functions including the network attachment and control, mobility management, resource and admission control. The network attachment and control as the name suggests obviously is related to the user equipment which is now attached to the network. So the attachment of the user equipment to the next generation network involves some kind of signaling, some protocol definition and all these aspects. So the network attachment is an important part only through which a user equipment has to be part of the overall NGN. Once the user equipment is attached, then the services need to be activated. So the usage of the services is another important aspect of the network attachment and control. The most well-known and understandable functions which could be and are actually provided from the network attachment and control functions are the dynamic IP address assignment because every time a user equipment connects to the network, a new IP address is assigned and once the user equipment is detached from the network, the IP address is released. Then the user equipment capabilities are to be negotiated and this negotiation can only take place once the network is aware of the resource availability on the user equipment. For that, some kind of automated discovery mechanism should be in place. For instance, what kind of encoding, decoding formats are supported by the user equipment. Having done that, then the next important phase is to authenticate the user equipment. Once the user equipment is authenticated and is determined to be belonging to some kind of legitimate user premises or user profile, then subsequent network processes could be initiated. That is, the user is then authorized. The authorization process takes place after confirming the validity of the user profile available in the database of the NGN. Then the access network, the underlying network is configured according to the service level agreement or the contract between the user and the NGN. In case of mobility or in case some location-based service is to be provided, location management becomes another important aspect of the network attachment and control because understandably when a user equipment is free to move, then some kind of automated attachment, detachment and reattachment mechanisms have to be defined. The next important aspect is the mobility management and control. That is, managing the mobility and controlling the mobility. First of all, the seamless IP mobility is a goal in the transport stratum. It means regardless of the source IP address or the originating IP address, when a user equipment is moving, when it leaves the parent network, enters a foreign network or re-enters the parent network, the IP address connectivity has to be managed in such a manner that the services are kept independent of it and the service provisioning is guaranteed. The seamless mobility implies to handle both kind of mobility scenarios. That is horizontal handover. Vertical handover means intra-technology handover when same radio access technologies or the radio access networks are considered. The vertical handover is more complex when different kind of radio access technologies are deployed and the user equipment is moving out from the premises of one and entering into the jurisdiction of another. There are no QS guarantees which is the scope of mobility management because mobility management just incorporates valid and all the time seamless connectivity. The mobility in the mobility management and control functions are assumed to be a service like a service which is independent of the underlying radio access technologies and the networks. Another important aspect of the control is the resource and admission control functions. As the name suggests resources, what all resources are available to the NGN, how these resources are managed to accommodate a growing number of users that is done through the admission policy. So the resource and admission control is essentially a link between the service control function and the transport control function. The service control function is related to the user domain and the transport control function is related to the network domain. So unless and until there is a strong binding or a relationship that is present between the service control and the transport control, the user equipments or the individual users cannot be offered services to their liking. So the resource and admission control includes the call establishment processes that is call and session admission control. So the admission control could be once a call is initiated, it could be admitted into the network, it could be simply or outrightly rejected or it could be admitted with some basic modification to the call requirement. The modification could take place depending upon the transport subscription information which is initially provided or requested by the service control function. The service level agreements, which is another obvious way to define how a service should be looking like, what all features should it include. The policies are another important aspect which play an important role in resource and admission control. And then we have the service priorities. The service priorities is similar to how we prioritize different kinds of data and users. For that we need to go into a little more detail into the resource and admission control function service priority levels. We have three priority levels that is priority level one, which is the highest. It is for the life saving or the emergency services which are provided on NGN. The medium level priority is the priority level number two. It is for the real time audio visual and video streaming applications. The cloud computing also requires level two and this VPN, the virtual private network kind of services also require that some kind of assured delay in tolerant services should be given higher priority than a priority which is known as the lowest priority. So priority level two is definitely superior to the priority level three. Priority level three is mainly concerned with transporting and controlling the traffic with least QoS guarantees and also there are no guarantees on the admission. It means when some kind of priority level three traffic is admitted into the network is requested to be admitted into the network. If the network resources are not enough then it could simply be denied. The examples for this level three priority traffic could be simple web and email traffic.