Method and system for measuring reception characteristics in a multicast data distribution group

Abstract

A method and system for accurately measuring the reception characteristics of receivers in a multicast data distribution group having a sending node and a plurality of receivers. The multicast group is organized as a repair tree in which selected nodes of the multicast group comprise repair nodes for downstream receivers. Multicast data packets transmitted by the repair nodes include a retransmission count field in addition to the multicast packet header information, a session identifier, a packet sequence number and payload data. The retransmission count provides an indication of the number of times the respective packet has been retransmitted in response to a repair request. The receivers include an original packet counter and a retransmission count counter for each multicast session. Each receiver increments the original packet counter upon receipt of a packet that has not been previously received. Each receiver adds the value contained in the retransmission count field of a received packet to the retransmission count counter upon receipt of a retransmitted multicast packet that corresponds to a packet identified as a missing packet by the respective receiver. The data in the actual packet count counter and the retransmission count counter is employed to generate a loss metric at each receiver that provides a measure of the reception characteristic of the respective receiver for the particular multicast session.