I think it's a bit of a stretch to include protocols and protocol suites among centralized services. One simple test for this is the question: "How many Xs are there?". For examples, how many email servers, FTP servers or terminal servers are there? Compare that with "How many Facebooks or GitHubs are there?".
Email protocol suite is designed to be federated. FTP is just a file system access protocol. But you could combine it with an inter-server filesystem synchronization protocol/service to make it a distributed federated service. And as for terminal servers,.. well, I don't think centralization makes much sense there. How can you achieve any of these with centralized services?
I talk about the past, your university FTP-Server was the central point to get your Software/Manuals also publish your work (today's Github/Sourceforge?). Your university Email Server was the primary central point to exchange Information mostly inside your university.
Again i talk about the past when email was primarily used to talk to other peoples often not even over a net but inside a mainframe thing.
I though i was clear talking about the past hence not including Facebook or GitHub, and btw. Email just became "federated" when everyone agreed to use smtp when talking over the internet.
Email protocol suite is designed to be federated. FTP is just a file system access protocol. But you could combine it with an inter-server filesystem synchronization protocol/service to make it a distributed federated service. And as for terminal servers,.. well, I don't think centralization makes much sense there. How can you achieve any of these with centralized services?