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. 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"). This "component approach" has many benefits, such as: a) separates API specification from implementation issues; b) allows modular deployment of service components; c) leverages recent advances in software development methodology; d) facilitates operation over standards-based infrastructure; e) frees application from knowledge of lower layers; f) allows applications and services to utilize modules dynamically; g) requires no use of vendor-specific tools or infrastructure. Further, we do not rely upon any vendor-specific tools or infrastructure, and have constructed the API to allow implementation either synchronously or asynchronously, with or without the use of threading.