It allows for flow-based semantics like in Transmission Control Protocol (TCP), but does not provide reliable in-order delivery.
Acknowledgments inform a sender whether its packets have arrived, and whether they were marked by Explicit Congestion Notification (ECN).
The long length of the sequence numbers aims to guard against "some blind attacks, such as the injection of DCCP-Resets into the connection".
As of 2017[update] such applications have often either settled for TCP or used User Datagram Protocol (UDP) and implemented their own congestion-control mechanisms, or have no congestion control at all.
First implementations have already been developed, tested, and presented in a collaborative approach between operators and academia [7] and are available as an open source solution.