This document is one of a series describing protocols associated with the Livermore Interactive Network Communication System (LINCS) hierarchical architecture. At the heart of LINCS is its basic interprocess communication (LINCS-IPC) service. LINCS-IPC defines a reliable, flow controlled, full duplex, uninterpreted, labeled bit stream communication service. LINCS-IPC is level 4 in the LINCS architecture. Level 3 of LINCS is the Network layer defining an internetwork datagram type service. LINCS-IPC interfaces to User processes that utilize higher level syntactic and semantic conventions for process interaction. The transport service provided by the Delta-t protocol can be considered a sublayer of the LINCS-IPC layer. Delta-t augments the Network level service as required to support LINCS-IPC. This document specifies the services provided by the Delta-t protocol to support LINCS-IPC, the operation of Delta-t, and the services Delta-t requires of the Network level. This document was written to be self-contained but the reader will find it useful to have available for reference the LINCS-IPC and LINCS DeltaGram Network layer protocol specifications. Implementations are underway in Pascal for the PDP-11 running under RT11 and RX11, in BLISS for the VAX running under VMS, in MODEL for the CRAY-1 and CDC 7600 running under NLTSS and LTSS, and for the SEL 32/75 running under PORT.