Patent ID: 7570635

Claim:
A multicast network unit, disposed between a first multicast network domain and a second multicast network domain, for delivering data to the second multicast network domain from the first multicast network domain, comprising: an extraction part for extracting first group address information within the first multicast network domain from said data; a holder part for holding said first group address information and second address information within the second multicast network domain so that said first group address information and said second address information correspond to each other; a judgment part for judging whether said holder part holds said first group address information extracted by said extraction part and outputting the result of a judgment; a filtering part which, when said result of judgment is holding, converts said first group address information to said second address information in said holder part corresponding to said first group address information and, when said result of judgment is non-holding, discards said data; and a transmitter part for transmitting data containing said second address information converted by said filtering part, to said second multicast network domains, wherein said filtering part is constructed so that it converts at least either said first group address information or second address information contained in said received data in dependence on a conversion rule held in said holder part.