SLE Routing – Simplified Station Access for Mission Operations

In the recent years ESA has adopted the CCSDS Recommendations for Space Link Extension (SLE) transfer services [1] as a standard interface for their TT&C station network (ESTRACK). Both ESA and external space missions interface ESTRACK Network via SLE services, which decouple the ESTRACK Users to a good extent from network implementation details. However, as of today, the SLE User (mission) requires some knowledge of the ground station configuration in order to establish the SLE links to the active communication chain. Furthermore, in case of a failure in the ground station active chain, mission and network operators need to coordinate the eventually required swap to the back-up chain. To overcome this relatively complex process, a discussion to simplify the current approach for the ESA Tracking Network has been started. In this context the idea of SLE Routing has been proposed and analyzed. SLE Routing shall basically route SLE Users’ connection to the ground station active chain without requiring the User to know a priori the station configuration; effectively the SLE User connects to the station only. This paper discusses in detail the requirements for the SLE Routing. Reliability and backwards compatibility, as well as failover scenarios and interoperability considerations are covered. We will discuss these requirements in the light of several implementation options. The importance of minimum impact on the current infrastructure to enable a robust, costand schedule-efficient solution is highlighted. The paper concludes with the trade-off of the considered options, which range from solutions based on connection routing to dynamic DNS (Domain Name Service) based approaches, and the preferred candidate solution. Finally, the current status is presented.