Binary,Keyword,Reference
00,Not-ECT (Not ECN-Capable Transport),[RFC3168]
01,ECT(1) (ECN-Capable Transport(1))[1],[RFC8311][RFC Errata 5399][RFC9331]
10,ECT(0) (ECN-Capable Transport(0)),[RFC3168]
11,CE (Congestion Experienced),[RFC3168]