Transcript VSI-E non-real time e-VLBI Trials

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 NyÅlseund, 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 1 2006
• 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