Methods, systems, apparatus, including computer programs encoded on computer storage media, for generating and routing modified multimedia data frames. In one aspect, the method includes maintaining, by a first network node, channel membership data that includes data indicating, for each channel of a plurality of channels, leaf node membership for a plurality of channels, and for each channel of the plurality of channels: determining, based on the channel membership data, the leaf nodes that are subscribed to access the channel, generating, based on the leaf nodes that are subscribed to access the channel, a modified multimedia data frame for the channel that includes (i) a hub node identifier, (ii) data that describes a destination address of each leaf node that is subscribed to access the channel and (iii) a payload, and transmitting, by the first network node, the generated modified multimedia data frame to a second network node.