 So far, we have become quite accustomed to and are very comfortable with the understanding of QS provisioning architecture in NGN. Specifically, the role of the transport stratum and the service stratum, namely the RSEF with its own functional entities and the service control function in the services stratum. But as we know that the services are provided end to end and beyond out, Ethernet is a very widely adopted Layer 2 technology on the exercise. So NGN actually adopts Ethernet both at the core as well as on the exercise we know the carrier grade Ethernet. So it is important to understand how Ethernet plays an ever increasing role in NGN architecture. Then we need to look at the requirements which consequently emerge. Now we know that Ethernet is widely adopted as the access technology for the corporate customers as well as the residential users. It goes much beyond the core networks from the exercise such as the Metro Ethernet which is a carrier grade Ethernet. Quality of service is usually adopted in the Ethernet through the incorporation of VLAN tagging protocol known as 802.1Q. Now with the provisioning of 802.1Q there's a whole list of requirements which are going to now accompany the quality of service provisioning mechanism through the tagging. Let's look at the overall generic architecture for Ethernet based NGNs because no doubt Ethernet is not going anywhere anytime soon. And we need to understand the importance of Ethernet from the exercise as well as the core side. So you see here that the customer premises network whether corporate as in business residential and even the mobile broadband networks are connected to the Ethernet network. The Ethernet network both on the access side and the core side are required to ensure quality of service mechanisms from the voice over IP, IPTV and other interactive multimedia traffic flows. So we are now going to look at the functional requirements. The first and foremost thing is that some kind of quality of service solicitation or requesting mechanisms should be provided to the end user which on the basis of a preconfigured service level agreement requests the quality of service for a certain flow. Correspondingly, the network side has to incorporate certain functionality to ensure that the end user in an end to end connection is able to receive the services not only from the access side also from the core side. The network side needs operation, administration and maintenance, some kind of load balancing and load sharing mechanism because it may not be directly related to quality of service provisioning, but the QoS can certainly degrade if the load is not balanced or shared properly. And in the wake of a failure some kind of protection port isolation and restoration mechanism should also be provided. Then we know that Ethernet is on the access side and it does not really bother about the virtual private networks which is more of a router based mechanism. So it means now that we are considering NGN which is Ethernet based and we are looking at the quality of service aspects, so VPN support also has to be provided. And then we know that VLANs are restricted to only the access side switches. But if we are considering the incorporation of Ethernet in the core, so VLAN mechanisms have to be extended to the core side as well. So some kind of discovery mechanism has to be provided across the core and access boundaries. So some auto configuration mechanism also has to be incorporated. Then the quality of service requirements have to be mapped to and fro between the core and the access side. And once the QoS mechanism is in place, so some kind of traffic management as in queuing and scheduling has to be incorporated.