This SAE Aerospace Standard (AS) specifies a data communications layer for the transport of messages defined by the Joint Architecture for Unmanned Systems (JAUS) or other Software Defined Protocols (SDP). This Transport Specification defines the formats and protocols used for communication between compliant entities for all supported link-layer protocols and media. Although JAUS is the SDP used as the example implemented throughout this document@ AS5669 can be used for any SDP that meets the required capabilities. A Software Defined Protocol is defined as an application data interface for communicating between software elements. The SDP is agnostic of the underlying communications protocol and in fact communicates in much the same manner regardless if the communicating entities are collocated in the same memory space or separated by a satellite link. Purpose The purpose of this document is to facilitate interoperation of systems by standardization of the Transport Layer for JAUS messages or other SDP. Compliance The JAUS / SDP Transport Specification must support compliance assessment. To do so@ this specification must be sufficiently precise to enable the ??compliant??/??not compliant?? distinction to be made at the Transport Layer; it should also enable the determination of this same distinction at the Application Layer. The JAUS Transport Considerations report [AIR5645] outlines compliance considerations in more detail ?C we only summarize the resultant Transport Rules here for usage with JAUS and other SDP payloads: Transport shall not modify the content or format of any transported payload. All Transport packets shall explicitly state the version of Transport. These considerations are supported by the standards defined in this document. Document Organization The Transport Specification defines a family of transports for the conveyance of SDP messaging among entities compliant with the specific SDP such as JAUS. It details message formats@ protocols@ typical operating environments@ and best practices. The Transport Considerations Report [AIR5645] provides background information and delineates criteria for the design of transports for JAUS messaging across various media and environments. In this respect@ the Transport Considerations Report serves as a meta-specification. The Transport Considerations Report explores the impact on JAUS messaging of each of the following: ? Characteristics of communications media. ? Characteristics of JAUS messaging. ? Requirements/constraints of unmanned systems operations. Field of Application The Field of Application for the Transport Specification is data communications between nodes on a computer network.