A Component Architecture for Platform-Independent Space Link Extension Services

-. We are proposing a novel method of specifying and implementing CCSDS Space Link Extension (SLE) services. Traditionally, such services would be functionally specified (perhaps via an Application Programming Interface, or API) and accessed via a "wire protocol" implemented on a physical network (e.g., TCP/IP over Ethernet). Specification of such a service interface at the "wire level" typically is used to guarantee interoperability between separate implementations (e.g., between both sides of an interface agreement). However, when issues such as security are considered (some of which have not yet been adequately addressed), such a wire-level specification is likely to severely limit future implementations and capabilities of the SLE services. We are therefore proposing a novel layered architecture for the SLE services, which frees each party from having to interoperate at the wire level; effectively, we move the interface from the wire to the service with significant benefits. Our approach thus specifies the SLE services as a set of software components that communicate with each other using standard invocation methods implemented on every computer (e.g., "subroutine call"). Our definition of a component is: "A standalone implementation of an object interface which provides standard ways to find and invoke its methods". This "component approach" has many benefits, such as: a) separates API specification from implementation issues (language, platform, etc.); b) allows modular deployment of service components; c) leverages recent advances in software development methodology, such as rapid d) facilitates operation over standards-based infktructure; e) frees application code from knowledge of lower layers; f) allows applications and services to utilize modules dynamically. prototyping and reusability; We finther propose to provide a layered implementation of these component interfaces, thus providing several options for a new kind of interface agreement: 1) one side could provide all the code implementing a specific wire protocol end to 2) each side could provide code implementing only its own wire protocol; end;