DCCP Simultaneous-Open Technique to Facilitate NAT/Middlebox Traversal

This document specifies an Internet standards track protocol for the
Internet community. It specifies an update to the Datagram Congestion Control
Protocol (DCCP), a connection-oriented and datagram-based transport
protocol. The update adds support for the DCCP-Listen packet. This
assists DCCP applications to communicate through middleboxes (e.g., a
Network Address Port Translator or a DCCP server behind a firewall),
where peering endpoints need to initiate communication in a nearsimultaneous
manner to establish necessary middlebox state.