Multimedia conferencing services have specific performance requirements with respect to the exchange of continuous media. One of these requirements is the synchronization within and between related streams. This article identifies synchronization requirements and solutions relevant for conferencing services that operate in an open distributed environment as defined in TINA-C. Based on the TINA service lifecycle, synchronization requirements and policies are described from different stakeholder perspectives. Synchronization is then specified in detail using the TINA information, computational and engineering languages. Finally, a description of the implementation of synchronization for a multimedia conferencing service is provided using a DPE platform. The synchronization object is proposed as an additional component available for the DPE that needs to deal with real-time audio-visual streams.