University of Helsinki The General Internet Signaling Transport (GIST) protocol specification supports two transport modes: UDP for very infrequent messaging, and TCP for all other cases. However, with TCP comes certain undesirable features, e.g., head of line blocking, which affect performance when a number of sessions are multiplexed over the same TCP connection. In certain environments and deployment scenarios, an unreliable, but still congestion controlled, transport would be needed. This specification proposes DCCP as a transport protocol for GIST.