The plan was presented at the inaugural Symposium on Operating Systems Principles in October 1967. Donald Davies' work on packet switching and the NPL network, presented by a colleague (Roger Scantlebury), came to the attention of the ARPA investigators at this conference. Roberts applied Davies' concept of packet switching for the ARPANET, and sought input from Paul Baran. The NPL network was using line speeds of 768 kbit/s, and the proposed line speed for the ARPANET was upgraded from 2.4 kbit/s to 50 kbit/s.