e-VLBI Trials Ny-Alesund to Haystack (VSI-E non real-time) C. Ruszczyk, J. Soohoo, A. Whitney [1], R. Hanssen, F. Koppang [2], O. Schjelderup, H. Eidnes [3], S. Bailey, D. Rubincam [4] [1] MIT Haystack [2] NMA, [3] Uninett folks, [4] NASA

Introduction Purpose: –Establishing a direct high-speed data link NMA Geodetic Observatory in Ny- Ålseund, Svalbard, to the MIT Haystack Observatory –The long term goal is to be able to deliver observation data in “real time”. Investigate e-VLBI Transfers –Viability of e-VLBI transfers –Transport protocol research / Analysis tools The NMA Geodetic Observatory in Ny-Ålesund

Introduction (cont) Trial –January 2006 – Sept Presently –NMA evaluating results –Determining if e-VLBI is viable Link exists for protocol testing –December 2006

Constraints End-System –Black out times existed Resource scheduling –Deadline Dates Transfers had to be completed Microwave Network Links –Rate limited (100Mbps) Self imposed (shared network) –Fall back position required Failures on microwave link (20Mbps)

Constraints (cont) TCP rate limiting –Standard linux traffic shaping Iproute2 Tc –Hierarchical token bucket –Classification of traffic Port, destination IP address UDP rate limiting –Responsibility of the application

Results Successful transfers –known file transfer applications (bbftp) –TCP –Performance problems Errors on the microwave link Result was reduction in maximum allowable bw –85Mbps Averaged about 65Mbps for transfers Peaks at 85Mbps –Reduced rate resulted -> longer transfers Network test issues: –Iperf tests Periodic dropouts (85Mbps) 22 secs – kernel daemon

Results (cont) VLBI Transport Application (vtp) –UDP –Rate limiting –Older motherboard effected application interaction Not observed earlier High end e-VLBI motherboards –Successful transfer of scan Lower than expected performance Under evaluation Side Note –Crashed Haystack network during testing –Not associated with the experiment –E-VLBI test machine sending malformed IP packets

Conclusion Some success / failures Interesting issues R&D Transfer –4.8 TB of data –Length of the scans Allowed to utilize network for continued research thru the end of the year. –Other transport protocols Integrated into VSI-E –Vfer, UDT Comparison