Experience with Reliable Multicast Data Streams in the EPS Core Ground Segment

Abstract

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In the EPS Core Ground Segment (CGS) network, IP multicast combined with the Pragmatic Generic Multicast (PGM) protocol is deployed to provide reliable point -to multipoint delivery of raw payload data streams from the ground stations to the central site, and of product data streams from the central site to users. The data streams are characterised. An overview is provided of the requirem ents and the design logic that have lead to the reliable multicast based solution being selected. Relevant technical detail is presented of the PGM/IP multicast configuration in the specific context of the EPS CGS network, characterised by multi -megabit da ta rates, local and wide -area network links - the latter of which a combination of terrestrial and satellite - and the presence of firewalls in the data path. With the data streams now being supported since the CGS validation and launch campaigns, and thro ughout the commissioning and routine operations phases, report is given on the experiences made so far. Performance and robustness is discussed as it has been achieved under nominal and deteriorated network conditions, versus the expectation to provide con tinuous reliable, lossless transmission. Issues that are specific to reliable multicast are highlighted, along with tuning and optimisation measures implemented to solve them. An outlook is provided on further enhancements planned. Based on the experiences gained, an assessment is made of the benefits and drawbacks of using reliable multicast in the CGS. As part of this assessment, the suitability of the solution to future EPS requirements is addressed.