Peter Kirstein has pursued international activities throughout his career. Through General Electric he was introduced to liaising with European science and technology. His further 25 years consulting with that company, and other similar work, were instrumental in giving an understanding of multinational companies. From 1973 to 2003, his research links with the US DARPA kept him well-informed about US network research. Indeed the SATNET project, in which he was one of the principal participants, was the first multinational project using a satellite in a packet-switched mode. Since 1984 he has continually been part of European Framework projects. From 1983 to 2003, he was the Chair of the International Collaboration Board, which fostered collaboration in unclassified Command and Control research amongst members of its participating NATO Defense departments.
During 1988-1993, Professor Kirstein was part of the review panel for the UNDP-funded ERNET project, which formed the nucleus of the Indian National Research and Education Network. He has served in similar roles in Australia, Canada, Germany and Norway.
In 1994 he was appointed as the UK member of the Networking Panel of the NATO Science Committee, eventually becoming its Chairman. While Chairman, he initiated the Silk Project, which was supported first by the NATO Science Programme and then its Public Diplomacy Division (NATO-PDD). From 2001 to 2010 he was Director of the Silk Project, which provided international connectivity between the European National Research and Engineering Networks and those of the Caucasus and Central Asia. Since 2010, he has been a principal consultant on PDD-supported Silk-Afghanistan – a project to establish a National Research Network for Afghan universities.