A document that regulates the security aspects of a proposed link between an agency and an external system. It regulates the security interface between two arbitrary systems operating under two different authorities. It contains a wide range of descriptive, technical, procedural and planning information. Generally, it is preceded by a formal MOA/MOU that defines higher roles and responsibilities in managing an inter-domain link. Source (s): CNSSI 4009-2015 In this manual, an agreement is reached between organizations that own and operate connected computer systems to document the technical requirements of interconnection. The ISA also supports a Memorandum of Understanding or Agreement (MOU/A) between the organizations. Source: NIST SP 800-47 as part of the Interconnection Security Agreement (ISA) Comments on certain definitions should be sent to the authors of the related source publication. For NIST publications, there is usually an email in the document. Comments on the presentation and functionality of the glossary should be secglossary@nist.gov.