 A very important aspect which is business oriented is the market aspect of the quality of service. ITUT defines four market models for QS. Why is this model needed? And can we understand it through a case study is the scope of this module. First of all, it is a market model. It means the quality of service is to be provided for commercial applications and services. Since most of the traffic, which is of concern from the quality of service point of view is the multimedia traffic on multimedia service platform. In NGN, since we have the service and transport strata, which are separate, so it means we can think about a chain of actions which are independent of each other, partly provided by the service stratum and partly by the transport stratum. These are the content creation, content delivery, its transportation and the end user perspective from the device angle as well as from the end users operation. All these four activities that we have just discussed are generally supplied, it means it is not inherent or intrinsic to the service. It means all these come together to provide services to the end users. Since they have independence, they are not totally dependent on each other, so each of these is responsible for its own installation, configuration, operation and maintenance. Since we now have four different actions, each action would now require different QS parameters and different QS classes. This four market model now becomes very interesting because it now serves as a benchmark or as a yardstick to identify the QS criteria for each one of them. As you can see here, these four markets starting from the content creation right up to customer equipment are related to the service provisioning and how the customer perceives the quality. Let's look at these four market forces or market components from a use case point of view. In this case, we can think about a user getting music content on this four market model on an NGN network architecture. Now this is a good case study because it involves the content as well as the consumer hardware. From the content perspective, the suitability of content, its popularity, whether it is a fad, the content is encoded in certain format which is highly suitable for high resolution or high fidelity music. Then there are certain aspects whether this service provider has addressed certain copyright issues and whether it is not original or if it is pirated. All these issues have to be considered from the quality of service point of view in the content creation activity. Then comes service provisioning. When a user is to be provided this music download facility, then navigation is an important facility through which a user can scroll through, for instance, a musician or different genre or by musical instrument. Then once a user commits to a certain file, music file to be downloaded, then it has to be a fair deal. The user's own privacy, its navigation history, the music download history should stay secure. The pricing has to be competitive and the customer has to be provided some kind of customer care so that a user feels satisfied and stays connected with the service provider. Now when a user has actually selected the content, then now the content actually has to be delivered. The network parameters including the bandwidth measured in megabits, kilobits per second, latency, jitter, if it is streamed live, if it is downloaded and played then latency is an issue, jitter is not an issue, but once it is streamed or it is streamed live, then it becomes an issue, then the error rate, if the network is joked or it has some contention, then the round trip time that is when a user clicks to when a user starts getting the service and while the file is being downloaded if there are certain distortion or noise related issues. The last activity or the action which is performed has to be the customer equipment related activities. For instance, if a customer equipment is not good enough, a good playback quality cannot be ensured. Does it have the right RAM or storage, the primary storage devices? Does the music player on the user equipment have features for selecting, playing, playing backwards, forwards, navigation and various kinds of downloading features available and then last but not the least is the user equipment ergonomically well suited to the user in terms of viewing, does it have some health hazards, etc. Now all these things actually come into the customer equipment related market. So these are four different market segments which are now included in ITUT for market model. This is a very good perspective on how quality of service has to be addressed from the service provider to the service consumer.