To access a communication managed by a host communicating entity between participant communicating entities including the host communicating entity via a packet network (RP), a third-party communicating entity transmits a message (MI) to the host communicating entity, which message comprises at least one parameter (PM) associated with an identifier of at least one participant communicating entity. The third-party entity's access to a peer-to-peer communication established between the host entity and a participant entity may create a conference between the three entities. The third-party entity's access to a conference communication may cause a participant to be added to the existing conference. The host communicating entity applies a restrictive policy on mixing communication flows exchanged between the communicating entities as a function of the parameter and the identifier of the participant communicating entity associated with the parameter.