 The content delivery on a multicast channel Was straightforward it got a little interesting when we looked at it from the roaming viewpoint, but the delivery of IPTV content over multicast is all together at a different level because there are so many options and recognized Functional modules which are all eligible for executing this multicasting So we will go through the functional models which have been recognized by the ITUT for NGN So essentially multicasting is different from unicasting because In unicasting the content is being delivered from one source to one destination But in multicasting it is one source to multiple destinations This actually means that are we going to Implement Dedicated circuits from the source to the destination are we going to make copies of the packets and come up with A tree that Is covering all the potential clients which are part of the multicast group that is all we are going to discuss in four different models So the four different models are The multicasting at the network layer. So it means it is the network multicast model. Then we have the cluster model Then we have the peer-to-peer model in terms of complexity in fact peer-to-peer model precedes cluster model because cluster model is more of Robust mechanism in which the network service provider takes more responsibility Then we can combine the cluster and the peer-to-peer model to realize the fourth type So let's look at the layered architecture of the overall NGN Framework in which we have the content provider service provider network provider and and user now these are four different domains or different boundaries in which the Equipment resides if we look at the content provider It is actually the application Function server that hosts the content then service provider actually means that it is the third party That is providing the services which actually has been developed by the content provider and then we have the network provider it is actually the network operator and Then we have the end user equipment if the multicasting is the responsibility of the network provider It actually means that we are looking at the multicast transport function at the network layer This means all the gateways the routers or the network equipment which is deployed by the network provider Will be responsible so we can call it more network-centric or network-based multicasting The peer-to-peer one is very simple in which we have a torrent like architecture where the individual users have their own proprietary mechanisms Which do not have any relationship with the network and they are executing this Multicasting by incorporating their own localized mechanisms, then we have the cluster model We call it cluster because the service provider which actually is Connected to the end user through the network provider has content delivery and service functions Dedicated for implementing multicasting so it means now the infrastructure or the servers are housed by the service provider This actually is more of a centralized architecture because here the service provider is Providing the multicasting services to the end users in a centralized or a singular manner Then we have the hybrid hybrid actually can take any form. It could actually even take the form of Incorporating the end user equipment and the network provider equipment But the network provider will not take that much of responsibility if the end user is already taking care of the multicasting so combining the The hybrid model Combines actually the cluster and the peer-to-peer model So we can quickly go through all of these to to fully understand the implications of using one over the other So network multicasting is actually where the Network provider or the engine provider takes a lead role. This is going to be implemented on the networking equipment So it actually uses multicast transport functions because the engine architecture has the transport stratum and the service stratum so in that case the end user equipment has to be Provided not only the connectivity but also the multicast support by registering As as a requester for the content with the engine provider This actually is implemented using a multicast group membership mechanism known as the Internet group management protocol proposed by the ITF There's another grouping mechanism that actually is known as the Multigroup management protocol, but Most of the time the ITF IGMP is also is mostly used so IGMP is basically a Logical network that overlays on a physical network. So this allows a membership based joining of Interested users in a certain content on a single group. This could include Hosts and routers which may be physically spaced apart, but they form They form logical agency Agency then IPv6 also has an equivalent because IGMP mostly works for IP version 4 So IPv6 uses the multicast listener discovery mechanism. It's a listener service that Runs on on on a server and listens to all the requests which want these content and Consequently allows these request Makers to join the multicast group So now since we are talking about The network so there's a close relationship between the content delivery performance and the network performance So the quality of network is going to Greatly influence the quality of service of content delivery. So any Change in the network parameters is going to have a direct bearing on the Content delivery performance as well. So two terms quality of service and Quality of network are going to be dependent now Then we have the peer-to-peer model. It's it's very simple because The responsibility of joining a group Making a request for a certain content Activating the streaming of the content providing the content getting the content are all managed by the user equipment So this involves a lot of software defined functionality on the end user equipment Once a particular peer In a peer-to-peer network Has the content it actually starts serving as a server for other peers So it means the distribution is done In a in a peer-to-peer manner. It has its own advantages But the most Obvious advantage is at the decentralization at the cost of compromise in terms of centralized management So the concept of peer-to-peer Content delivery It results into some kind of discovery mechanism that that is implemented if you recall the BitTorrent architecture, we have the The peers which join a network and they form a kind of a distributed hash table based Network in which each neighbor discovers another neighbor And Makes an explicit request for the content So the beauty of this actually has the flip side also because in the absence of a centralized Server entity we can have some compromise on the traffic quality If a certain peer is available or not and subsequently the Concept of billing more gets more complicated Then we have the cluster model The cluster model actually heavily depends on the content Distribution function that is there in the service provider And this actually is based on servers So the capacity of the servers to accommodate a certain number of users is directly going to influence The overall experience of other users as well Combining the cluster based approach Which is centralized and the peer-to-peer approach results in the best of the two worlds Resulting into a hybrid model So the beauty about hybrid model is that This management is centralized The distribution is peer-to-peer that results into a lot of scalability and robust control and a decent quality of QOS so this is a quick recap to what we've already seen in terms of Multicasting peer-to-peer cluster and hybrid