 Now that we have looked at some of the potential deployment strategies for FTTH, it is important to understand what are the variants of FTTH and in principle how these variants differ from each other with regards to the principle, the methodology and their suggested or perpetrated objectives. For that we'd look at some of the very basic considerations that are important in determining what is the most suitable deployment strategy for the FTTH networks on the access side. Then we'd look at the characteristics of different architectures and deployment mechanisms and finally we'd quickly look at the first variant of the FTTH access network, the P2P optical distribution network. So let's start. First of all, since it is all related to the cost of the technology deployment, the speed at which FTTH technology can embrace the market and would get user acceptability is determined by its direct comparison to the overall cost incurred in deploying the hybrid solutions namely the XDSL and HFC. It is important to understand that part of the legacy network is already based on coaxial cable and unshielded twisted pair so it means FTTH all optical deployment has to be really very smart and with reduced costs. Consequently, depending upon the user requirements, the FTTH network architecture and the corresponding distribution network is determined by certain characteristics. Let's look at them. The architectural characteristics include, first of all, the location of the electronics which would be used both at the central office and at the user premises. Since the traffic from the users would be aggregated, so how the bandwidth is aggregated at the central office, what is the electronics involved in it is also an important architectural consideration. Then what is the upper bound or what is the user requirement in terms of bandwidth allocation? Is it traffic dependent that a user uses? Is it user specified as in the service level agreement? And then what is the handshaking mechanism between the equipment that would be deployed on the customer side and on the central office? And last, not the least, that the mechanism to allow the central office to communicate with individual user premises equipment is either in a point to point manner or point to multi-point fashion. So the first one of course is the point to point optical distribution network. It is very simple, it is straightforward. That is, from the central office to each user equipment, a dedicated fiber link is established. So as a consequence, the total number of fibers required to be laid is equal to the number of home subscribers which are planned in a certain business model. It is important to consider here the overall cost for, for instance, digging, taking permissions and certain clearances from the government. And then again, once you've deployed the fiber, then covering up, refilling that particular trench and then probably doing the, the bricklaying or the cladding off-road as well. So the P2P mechanism, the optical distribution network is obviously the best because it is based on a dedicated fiber between every user and the central office. So maximum throughput can be expected. However, the flip side is also very important that it is the least cost effective mechanism. Of course, individual fiber laying is certainly not feasible. Because of such fiber deployment between the central office and the user equipment, two end-to-end electronic deployments have to be considered. The first one is at the central office. It is known as the optical link termination or the optical line termination. The optical line termination actually means it is the electronics that terminates the link that comes from the user side. And on the user side, it is known as the optical network termination. It actually means this is the user side where the central office network is terminating. If you just look at the figure, we shall clearly understand that the central office and the users are all connected by a certain number of fibers, which linearly grows as the home users grow. Now, in case of the fiber to the curve, I mean, we are considering fiber to the home, but in case of fiber to the curve, the termination unit on the user side or at the home is known as the optical network unit. It is just a terminology that distinguishes it from the optical network termination device.