Abstract: A method for computer-based communication includes storing at a first computer records of correspondence between application-specific identifiers used in a network application and network addresses of computers on a network that are respectively associated with the application-specific identifiers. A second computer is powered down after storing at the first computer a record of the correspondence between an application-specific identifier and a network address associated with the second computer. If it is determined, while the second computer is powered down, that a message is to be directed by the network application to the application-specific identifier associated with the second computer, a wake-up packet is sent over the network to the network address specified by the record, so as to cause the second computer to power up and respond to the message.

Abstract: A method for communication includes specifying a group of packet telephony terminals that are to participate in a telephone conference. Based on the list, a conference topology is defined in which at least two of the terminals serve as bridge nodes, which are associated respectively with mutually-disjoint sets of the terminals. Telephony connections are set up over a packet network between first and second bridge nodes, and between the first bridge node and each of the terminals in a first set of the terminals, and between the second bridge node and each of the terminals in a second set. Audio signals conveyed over the telephony connections are mixed at each of the bridge nodes so as to join the first and second sets of the terminals together with the first and second bridge nodes in the telephone conference.