FreeBSD 8.0 and NetBSD 4.0 implement ECN support for TCP; it can be activated through the sysctl interface by setting 1 as value for the sysctl net.inet.tcp.ecn.enable parameter.
FreeBSD 8.0和NetBSD 4.0为TCP实现了ECN支持，可以通过sysctl接口将net.inet.tcp.ecn.enable参数设为1来激活。