 So far we have seen passive optical networks and we have gone into into the due detail The only difference between the passive optical network and the next generation active optical networks is going to be in the devices in this module we quickly look at the Overview of the topology that is not going to be much different from passive optical networks Then we'd look at the way how traffic engineering can be implemented in Active optical networks through the adoption of the control plane as in GMP LS So let's start with the topology first The topology for active optical network is not very much different from passive optical network Both of these actually are based on the concept of aggregation and Splitting however the fundamental difference between passive and active is surely going to be there we had Passive splitting and passive aggregation here. We are going to have Active elements such as switches these switches replace those Plitters and that is all The active optical networks are essentially end to an Ethernet based like passive optical networks and of course The switches at the central office are going to be essentially the same as the aggregation switch So once we were doing passive splitting and passive aggregation here. We are going to have active aggregation through these switches let's look at the overall network of How the AON is going to look like if you look at the Inside we have the next generation access network and we have a home network The access network is looking like a mesh and indeed it is a mesh Here we have different access network sites It means each of these is a network with users connected to it All these are connected in a mesh formation on the right hand side We have the core network. It actually means that the entire access network or a mesh of Access networks is connected to the core network. The core network could be any other technology or it could also be based on Basically active optical networking However, in order to provide interfacing between these two we need access edge site that is some kind of The network to network interface on the left hand side. We see that we have different home networks these home networks are Essentially small networks which are housed within a single building either for the residential use or for commercial use However to provide interfacing with the access network. We need the gateways as the premises gateway sites Now with this Overall understanding. We just look at the mesh networking concept of it The next generation all optical Active optical networks are based based on the concept of mesh as you know Mesh actually has more than one links between two vertices So it naturally is meant to achieve something at the cost of extra fiber optic deployment This is to achieve number one flexibility and number two higher Recoverability in the case of fiber cut or some natural or man-made disaster These devices which are connected to each other are connected through the gateway sites That we have already discussed. There's a provision to have more than one Connect access network connectivity through the gateway site to provide resilience as well And then the core network is connected through the access edge site that we've already discussed Now for this active optical network There's a requirement to provide management services And to provide better quality of service through traffic engineering In in these next generation Active optical networks the traffic engineering and unified Network management that is the control plane is achieved for access distribution and the core through Variant of MPLS called the generalized multi protocol label switching So GMP LS is basically a general Labeling protocol Labeling and switching protocol that works for these active optical networks because Not only IP is going to be there because there are certain other switching techniques which have been there either as legacy Legacy systems like the time division multiplexing wavelength division multiplexing or even fiber link switching So in order to accommodate all these some kind of unification was required So GMP LS can be used to provide the traffic engineering and unified network management Now GMP LS actually has been there for for quite a while as a control plane for Pave length division multiplexed optical networks however, it can be easily interfaced for Ethernet because Ethernet is a layer two to policy technology all these GMP LS The MPLS and GMP LS variants can actually work at the Shim layer or the layer below the detailing layer. So Ethernet frames can be encapsulated within these MPLS Frames, so this concept is known as Ethernet tunneling We may look at it in more detail once we come across Ethernet tunneling But for now just understand it is a means to encapsulate Ethernet frames within GMP LS frame structure