Explicit Congestion Notification (ECN) slows down outbound connections

Windows Server 2012 is the first Windows Server version to enable Explicit Congestion Notification, or ECN, in the TCP stack. This is also known as ECN Capability. Explicit Congestion Notification is an extension to the Internet Protocol and to the Transmission Control Protocol and is defined in RFC 3168. ECN allows end-to-end notification of network congestion without dropping packets.

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