Defense Advanced Research Projects Agency. U.S. government agency that funded research for and experimentation with the Internet. Evolved from ARPA, and then, in 1994, back to ARPA.

Defense Communications Agency. U.S. government organization responsible for DDN networks such as MILNET. Now called DISA.

Defense Information Systems Agency. U.S. military organization responsible for implementing and operating military information systems, including the DDN.Search request sent to a specific node known to contain a resource. A directed search is used to determine the continued existence of the resource and to obtain routing information specific to the node.

It is a large (10-20 ?m diameter) amoeboid and phagocytic cell found in many tissues, especially in areas of inflammation, derived from blood monocytes and playing an important role in host defense mechanisms.

It is a measure that if for some reason all of your revenues were to suddenly cease, the Basic Defense Interval (BDI) helps determine the number of days your company can cover its cash expenses without the aid of additional financing. The BDI is calculated: (Cash + Receivables + Marketable Securities) / ((Operating Expenses + Interest + Income Taxes) / 365) = Basic Defense Interval.

Defense Data Network. U.S. military network composed of an unclassified network (MILNET) and various secret and topsecret networks. DDN is operated and maintained by DISA.