The first ARPANET node outside the US was established at Kjeller, Norway in June 1973 for the NDRE researchers, and by the end of July 1973, an ARPANET node was also set up in the U.K. at the University College London. Spilling visited Professor Peter Kirstein's research group at UCL in 1974 and worked with Vint Cerf, then junior assistant professor at Stanford University, on the then proposed Transmission Control Protocol conducting the first TCP tests between different implementations.