--Gordon Knoble (gene.g.knoble.1@gsfc.nasa.gov), EOSDIS Project, Goddard Space Flight Center
The EOSDIS networks support a diverse set of data flows, from raw telemetry data received at the ground stations to science products delivered to the end users. These can be grouped into mission operations flows and science data distribution flows as summarized below:
Mission operations network requirements are derived from the instrument data rates and the locations to which the data are to be sent as documented in Earth Science Data and Information System (ESDIS) Project Level 2 requirements and various inter-project agreements. Science data distribution network requirements are derived from information regarding product sizes, production rates, Instrument Team member locations, and flow requirements provided to the ESDIS Project by Instrument Teams. These requirements were formerly collected through the Ad Hoc Working Group on Production (AHWGP) and resulted in the establishment of the "February 1996 Technical Baseline." This is the baseline with respect to which the budget is computed and adjustments are made as changes occur (e.g., the Biennial Review Committee's recommendation to ramp-up generation of higher level products). Changes to the requirements requested by the Instrument Teams are submitted to the Data Processing Resources Board (DPRB) chaired by Skip Reber (Deputy EOS Senior Project Scientist and Acting EOSDIS Project Scientist). The ESDIS Project's networks group supports the DPRB with analyses of cost impacts and other implications on implementation that result from the requested changes. In the past several months the networks group has performed analyses of proposed changes to the February 1996 Technical Baseline and provided cost and schedule impacts to the DPRB. Requirements changes are analyzed by the ESDIS Project and NASA Integrated Services Network (NISN) for their effect on the existing infrastructure. The raw data flow requirements have various functions applied to arrive at the implemented data rate capacities. These functions account for network loading and other network performance characteristics, network protocol overhead, network and end system downtime, and several other factors which clarify DAAC data pull characteristics.
The EOSDIS networks consist of the NISN EOS Backbone Network (EBNet), and the NASA Internet (NI). The EBNet supports EOS mission operations and inter-DAAC flow of science data for standard data product generation. The NI supports EOS science data distribution to the Instrument Teams' Science Computing Facilities to assure the basic level of connectivity needed to support data flows for performing timely quality assessment of standard data products. Large data flows, such as EDOS-to-the-DAACs and DAAC-to-DAAC, are being implemented on the NI (ATM) backbone, procured from Sprint. The ATM backbone implementation is replacing the existing backbone based on dedicated circuits. Data flows to non-NASA instrument team sites use existing Internet connectivity or tail circuits to the NI. The NI circuits are installed, or existing circuits upgraded, at the ESDIS Project's request based on the requirements and currently available performance. For those customer sites with shared resources, the present circuit load is monitored, and in some cases the link is tested by installing a test program at the user site to exercise the link. Depending on the results of the monitoring and tests, the link may be upgraded, or other options explored. The ESDIS Project is currently performing an assessment of the user sites, and is testing the performance of many sites' existing connectivity to determine if the performance meets the user requirements.
The ESDIS Project is actively working with other organizations to apply emerging technologies to increase network performance and reduce cost. Three notable activities involve an agreement to use the National Science Foundation's (NSF) "very high speed Backbone Network Service" (vBNS) for EOS science data distribution, consolidation of numerous EOSDIS related network connections in the Boulder area, and participation in the Great Plains Network Consortium, which should improve EROS Data Center (EDC) DAAC connectivity. Through a pending agreement with the NASA Research and Education Network (NREN) and the NSF, ESDIS Project has negotiated use of the vBNS to support the distribution of science data to non-NASA sites. Approximately 25 EOS science team sites are served by vBNS, providing DS-3, 45 Megabits per second (Mbps), OC-3, 155 Mbps, and higher speed connections to the sites. The vBNS connectivity to the DAACs will be provided by NREN. In exchange for this service, EOSDIS sites may be asked to participate in any of several network prototype activities. A meeting will be held at the end of May with the Boulder area organizations to plan a consolidation and, ultimately, connection to the NI ATM backbone. The Great Plains Network Consortium is currently having discussions to solidify requirements and participation in the network.