382 CHAPTER 6 Application: IPTV End-user Network Servers Service Provider Content Servers FIGURE 6.1 The focus of this chapter is to discuss IPTV as an application in a multicast environment. In a simplistic way, IPTV architecture can be broken down into four domains (see Figure 6.1 ): 1. Content Domain: In the IPTV world this domain is where the content is generated. These could be studios or individuals who in turn provide this content to the service providers who broadcast this content to end users. The content domain is outside of the scope of this discussion. 2. Head-end Domain: This part of the architecture deals with the aggregation of content that is to be sent to the end user. The head-end section of the architecture contains functions such as content preparation, personalization, and back-end functions such as subscription management. Content preparation would entail the generation of multimedia content in a digital format, the necessary storage infrastructure for VoD content, the necessary satellite infrastructure to receive content from other networks, and so forth. Personalization of EPG and customer profile management are personalization functions. 3. Transport Network Domain: Usage of multicast technologies in the transport infrastructure for the purpose of transporting IPTV content is the area of focus for this chapter. As transport net- work is studied in further detail, it is broken down into the long-haul transport and the last-mile (access) infrastructures. The standards associated with IPTV transport, aspects such as quality of experience (QoE) and how IP quality of service (QoS), are tweaked to provide the necessary sup- port, and some of the challenges relating to the implementation such as ensuring minimal channel change time (zap time) are discussed as a part of Section . 4. Home Network Domain: aspect of the IPTV architecture deals with the STBs/CPEs This deployed at the end-user premises to facilitate IPTV. CPEs are far more sophisticated than the STBs with an F-connector. Today's smart clients have decoding, storage, and networking as well as Web-based client interfaces bundled into a single device. 6.2 IPTV STANDARDS IPTV architecture for each major operator is a walled garden, with a customer-engineered solution from the head end to the end user. Multi-service operators (MSOs) most often rely on the capabili- ties of the vendor equipment about what services can or cannot be offered and service flexibility is curtailed by the product road maps. While such a situation is unavoidable in the nascent stages of the