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 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