RFC 3540 described an optional usage of the ECT(0) and ECT(1) codepoints in the IP header to verify the correct behavior of an ECN receiver and verify that that there is no other interference that conceals marked (or dropped) packets in the signaling path, for use in experimentation. While the ECN Nonce works as specified, and has been deployed in limited environments, widespread usage in the Internet has not materialized. With the emergence of new experimental functionality that depends on use of the ECT(1) codepoint for other purposes, continuing to reserve that codepoint for the ECN Nonce experiment is no longer justified. The TSVWG working group has requested that this experiment be explicitly concluded, and RFC 5340 moved to Historic status. Further explanation and description of recent tests to measure ECN Nonce usage on the Internet is available in draft-ietf-tsvwg-ecn-experimentation, Section 3.