P2PSDE : Peer-to-Peer Science Data Environment Authors : J. Byrnes, M. Holland

1. To advance our understanding of the relationship between the dynamic solar wind and near-earth geospace, the Wind spacecraft records the sol;r P2PSDE (root-group) peers and (global) services groupA peers and services groupB peers and services groupZ peers and services groupA RPV groupB RPV groupZ RPV P2PSDE RPV gateway RPV WindSWE services IMP8plas services Dev. file- share serv. WindMFI services IMP8mags services P2PSDE: Peer-to-Peer Science Data Environment Authors: J. Byrnes, M. Holland NASA/GSFC (Code 587) Advanced Data Management & Analysis Branch Information Systems Division, Applied Engineering & Technology Directorate Abstract The goal of P2PSDE is to provide a convenient and extensible P2P network architecture that allows distributed science-data services; seamlessly incorporating collaborative value-added services with search-oriented access to remote science data. This “virtual network overlay” supports the direct communication and automatic collaboration of real-time discoverable peers —regardless of heterogeneity and partitioning in the underlying physical network. We present the advantages of P2P networking over the conventional client-server paradigm and describe the Environment’s robust (with respect to load-balancing and network failure), dynamic, self-organizing design strategy. Details of the current SDE implementation (and its basic features) are discussed, and the future developmental direction of the SDE is outlined. Collaboration with science community members will be central to this future. • Peer-to-Peer (P2P) networking is an alternative to the more asymmetrical, centralized, client-server approach; the idea being that, at any given time, any peer may offer services to any other peer, so that peers may take on whichever of the roles of “client” or “server” suits their immediate need. When managing science data, this has advantages over using a single, monolithic, central server to serve all clients of a stand-alone service: • Decentralized use of small, inexpensive, readily-available desktop machines • Virtually infinite (with many machines participating) storage/bandwidth. • Avoids storage/bandwidth (and evolutionary) bottlenecks associated with large, centralized, expensive data-centers—unlikely to evolve much after inception. • Co-opting existing data-services by incorporating their centralized servers • Any existing server of a stand-alone data-service may be easily incorporated into the SDE as a peer, withoutthe need for any re-definition of original stand-alone service. • Entire existing data-centers and Virtual Observatories could thus be co-opted. • Openness/extensibility; freedom to include “working” data-sets/services • New data-sets/services may be easily added to the SDE at any time. • Specialized and/or prototype science data-sets and services, which may never be otherwise made available to the science community, could be included in the SDE. • P2PSDE features the real-time discovery of all elements of the SDE—no need for a human webmaster to maintain a central registry. Every participating peer can dynamically discover the other SDE peers and services within the hierarchical peer-groupings of the Environment. All science-data services are searchably organized by the scientist-user’s interest-area, with peer-group boundaries defining the current search scope—with the potential for overlapping and/or hierarchical searching scopes. Additionally, arbitrary levels of Quality-of-Service and reliability may be achieved through the cooperation of redundant instances of a stand-alone service (automatic within the same group). • The figure on the left depicts a generalized self-organizing SDE, where both incoming data-serving and data-browsing peers “rendezvous” with a series of cooperative groupings of “super peers”, called “Rendezvous Peer-Views” (RPVs), before joining each peer-group and participating in that group’s services. Arrows depict the direction of all discovery-references, since the information discovered at the rendezvous “points” to the discovered resources. In a sense, an RPV is a bulletin-board where advertisements of group-resources are posted for later discovery by any other peer “checking in” with that group-RPV. P2PSDE peers are pre-configured with all that is needed to contact gateway RPV. any peers (using JXTA) on the "open" internet The figure on the right displays a prototype SDE currently under development. This SDE consists of five “child” groups and the P2PSDE “root” group. In the ‘Dev’ group text files of interest to developers are shared. No services (except for “core” services like discovery) are currently offered in ‘P2PSDE’. The four remaining groups are overlapping in that the data-services offered have some commonality: “WindSWE services” (serving data from Wind/SWE) are available both by joining the ‘Wind’ group and by joining the ‘Plasma’ group. However, any peers in the ‘Wind’ group also have Wind/MFI services available; and, similarly, when in ‘Plasma’ IMP8 (and any other plasma-data) services are also available. Browser-peers may join any of these groups at will; the group organization in the prototype SDE simply facilitates users’ accessing of services by interest-area. More complex, hierarchical groupings are possible. P2PSDE The current SDE implementation supports only the sharing of files; users of a given SDE service are limited to simply downloading the files available on the server. The most basic services in the current implementation allow the shared content to be searched by filename only (e.g. 200208??.dat matches all shared *.dat files from August 2002). More advanced services are under development; allowing shared files to be searched by their contents (e.g. a user may search for all daily magnetometer files—from any spacecraft within a given region of space—where the measured B-field has some desired characteristic). It is anticipated that future development of the SDE will involve the type of distributed computing required to serve any requested data in the end-user’s desired format. In the ultimate implementation of the SDE, many value-added services easily augment existing services through seamless, collaborative P2P techniques for combining existing services and/or transparently transforming served data from its originally-served form into some other, more desirable form (new file-format, engineering units, coordinate system, etc.) without any additional time and/or effort on the part of the end-user. This will require a high-performance system capable of maintaining high levels of security. Wind group IMP8 group Plasma group Dev. group Mags. group