 Now we are going to understand how the transport stratum functions are organized. Specifically, we see that the transport stratum functions are organized into the transport functions themselves and the transport control functions. We are going to devote couple of modules to the transport stratum function and we will go into the due detail. The transport functions are related to the physical network resources. When we say physical, it means it can be classified as the NGN architecture, hardware and software, which can be seen as comprising the two parts, the network part and the routers part. The network part addresses and encompasses the access network and the core network and the router part comprises those edge routers which are between the access and control routers. These routers are also termed as the gateways. The transport functions are essentially the network part and the interconnection part as we just discussed the gateway routers part. The access network functions are to begin with these but definitely there is an increase and extension to the existing scope of the functions for the transport stratum. So the access network functions include all the aspects which are related to the user side that is the access network functions include user traffic aggregation that is to pick up user streams coming from individual user equipment and aggregating them onto a single pipe. This also includes the access mechanism that is the control to and from the connectivity between the access network and the core network. This is together with traffic aggregation executed under the umbrella of QoS. It means the access network functions also include the implementation of the quality of service on the access side. Now as you may wonder if the quality of service is that an important functionality then what are different aspects which are provided by the access network functions. First it is scheduling. Scheduling deals with prioritizing the outflow of traffic. Then we have the buffer management for instance when the packets are high faster than a network element can handle then some process has to be executed to manage that situation. Then we have the classification of traffic according to the service level agreement or the policies which the network implements. The filtering of traffic depending on what is permissible what is not which traffic class has to be penalized which has to be given high priority so some kind of filtering mechanism should be in place. The traffic shaping is responsible for smoothing of traffic flow that behaves a little erratically. Policing is the enforcement of a certain administrative policy coming from the policy makers the business interest group and the overall management. Of all these if it is the wireless environment then all these are applicable on to the mobile environment so the mobility support is another important QoS parameter which should be implemented. There is a support for some basic networks but it is not necessarily limited to these only. The supported access networks include the DSL network types. To begin with although DSL is on the twisted pair some variants of DSL are coming on to optical as well. So using the DSL technology is one of the focus groups for the access network functions in the transport stratum function the transport part. Then the cable networks are also supported the DOCSIS architecture the packet cable networks all are covered under the same umbrella. In the wireless side we have the Wi-Fi 802.11 the Wi-Max the universal mobile telecommunication systems the long term evolution and long term evolution advanced that we know as 4G and all those networks. Then the optical access that is fiber to the curb fiber to the home we would come across these terminologies at appropriate time but for now you need to understand that these are the access network supported under the transport stratum. The edge functions as we discussed are related to providing interconnectivity. So the traffic which is aggregated from the access network and sent on to the core network is the responsibility of the edge function. And the interconnectivity of the core networks that is the intra core network connectivity is also the scope of the edge functions.