ip Project (3GPP) as a major component of IP Multimedia Subsys- tem (IMS). This chapter explains the SIP capabilities of building advanced media services and the possibilities of performing advanced services in a SIP environment. In Section 2.2, the SIP application server and the control of media servers are explained as the basis of value-added service implementation and delivery. After that, in Section 2.3, the SIP SOA paradigm is described. In Section 2.4, an important feature of SIP, flexible control and management mechanisms based in SIP, such us cross-layering, are drawn. Section 2.5 covers the foresee- able role of SIP in the Internet of the future. This chapter ends with exper- imental results of these concepts, developed within the scope of the i2CAT Foundation. 2.2 Building Advanced Media Services From the architectural point of view, a SIP platform can be composed of elements grouped in two categories: clients and servers. SIP clients can act not only as User Agent Client (UAC), but also as User Agent Server (UAS). For instance, they can be a SIP terminal, (e.g., a VoIP C 2009 by Taylor & Francis Group, LLC SIP: Advanced Media Integration telephone in the case of IP telephony), and SIP gateways. These are devices that provide services such as formats translation and communication proce- dures between SIP terminals and non-SIP terminals, or transcoding between audio and video codecs. Commonly, SIP servers work as proxy, redirect, and registrar. Besides these types, two other servers have special relevance to developing advanced media services: media servers and applications servers. Media servers allow the possibility of having immediate access to any audio- visual (audio and video) content stored in their repository. When users request this type of services, they should know, only and exclusively, what service to request or with whom they want to communicate. With current paradigms, when users ask for access to streaming content, they should know which server will provide them this content. They should