The recent growth of peer-to-peer traffic and the popularity of streaming video is a cause for possible instability of the networks because most of these services run over UDP, without any mechanism for congestion control. Moreover, the adaptive features of peer-to-peer traffic may lead a misuse of the classical QoS rules legitimately applied to end-user applications. This paper proposes the usage of the Partial Reliability extension of the Stream Control Transmission Protocol (PR-SCTP) as the unique transport entity in an IP Multimedia Subsystem (IMS) network control and access layer, to mitigate situations of traffic congestion. The IMS is a 3GPP standardized approach that enables convergence of data, voice, video and mobile network technology over an IP-based network. Session Initiation Protocol (SIP) and Session Description Protocol (SDP) are the groundwork to support the convergence proposed by IMS. PR-SCTP provides several features to improve the transport of SIP between the IMS entities and after introducing the motivation to this proposal, we discuss and compare the benefits and drawbacks of using PR-SCTP instead of TCP or UDP to transport SIP.