Changes to the wire protocol have come about since the the TOPDISC paper. The ADNODES response was deemed necessary to tell apart the double set of inbound NODES responses to a TOPICQUERY as according to the paper, once with advertised nodes and once with nodes to fill the topic's kbuckets. An implementation currently in review https://github.com/sigp/discv5/pull/126.
Changes to the wire protocol have come about since the the TOPDISC paper. The ADNODES response was deemed necessary to tell apart the double set of inbound NODES responses to a TOPICQUERY as according to the paper, once with advertised nodes and once with nodes to fill the topic's kbuckets. An implementation currently in review https://github.com/sigp/discv5/pull/126.