DAP - Data Access Protocol (DECnet)

DCAP - Data Link Switching Client Access Protocol 

DCP - Data Compression Protocol over Frame Relay

DCPCP - DCP Control Protocol

DDP - Datagram Delivery Protocol (AppleTalk)

DECnet - Digital Equipment Corporation protocols developed to communicate between DEC minicomputers.

DHCP - Dynamic Host Configuration Protocol (TCP/IP)

DIAG - Diagnostic Responder protocol  (Novell)

DLSw - Data Link Switching (IBM SNA)

DNCP - PPP DECnet Phase IV Control Protocol (PPP suite)

DNS - Domain Name Server protocol (TCP/IP)

DSMCC - Digital Storage Media Command and Control (Audio Visual over ATM)

DVB - Digital Video Broadcasting