University of Oslo University of Oslo Swinburne University of University of Aberdeen This document relaxes recommendations and prescriptions from RFC3168 and RFC4774 that get in the way of experimentation with different ECN strategies. First, RFC3168 and RFC4774 state that, upon the receipt by an ECN-Capable transport of a single CE packet, the congestion control algorithms followed at the end-systems MUST be essentially the same as the congestion control response to a single dropped packet. This document relaxes this rule in order to encourage experimentation with different backoff strategies. Second, this document allows future IETF specifications to use the ECT(1) codepoint in ways that are currently prohibited by RFC3168. Third, this document allows future IETF experiments to use the ECT(0) or ECT(1) codepoint on any TCP segment.