The Session Initiation Protocol (SIP) is nowadays widely used as the primary standard application layer signaling protocol for multimedia sessions in the Internet. Furthermore, it is considered as the core protocol for the IP Multimedia Subsystem (IMS) of Next Generation Network architectures. Resources in the Internet are, however, still committed only on a best-effort basis, which proves to be especially problematic for real-time interactive applications, such as Voice-over-IP (VoIP) telephony. In order to reserve the correct amount of resources for multimedia sessions from end-to-end Quality-of-Service signaling protocols are necessary. This paper shows how a SIP-based setup of a multimedia session can be coupled with an advanced Quality-of-Service signaling solution. We present an analysis of the required SIP protocol mechanisms, show how the resource reservation request interacts with the SIP signaling request, and evaluate the duration of the overall signaling process using a prototypical implementation.