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The First Implementation of RTP Framing for e-VLBI

Amanda Morrow morrow@physics.arizona.edu. David Lapsley dlapsley@haystack.mit.edu. Alan Whitney awhitney@haystack.mit.edu. Past problems: Traditionally, VLBI data is stored on tapes/disks and shipped to a central location for processing, but results could take weeks due to shipping.

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The First Implementation of RTP Framing for e-VLBI

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  1. Amanda Morrowmorrow@physics.arizona.edu David Lapsleydlapsley@haystack.mit.edu Alan Whitneyawhitney@haystack.mit.edu • Past problems: • Traditionally, VLBI data is stored on tapes/disks and shipped to a central location for processing, but results could take weeks due to shipping. FTP has been used but it was not designed for high bandwidth or long distances. Fact: The average usage of networks like Internet2’s high speed Abilene network is less than 20% in the long term. The First Implementation of RTP Framing for e-VLBI However, e-VLBI can take advantage of this currently unused network! With telescopes all over the world how does the data get to a correlator for processing? What is the best way to ship data over long distances quickly? • Other advantages of e-VLBI: • Faster turnaround of results • Higher sensitivity • Lower costs • Quick diagnostics and tests • RTP provides a standard format for: • Transmission of sampled analog data • Dissemination of session information • Monitoring of network performance • Adaptation to varying network • Appropriate reliability/ repair model • Multi-cast distribution of statistics What e-VLBI needs: Efficient transport mechanism Standard protocols Internet-friendly transport Scalable Implementation Ability to multicast Fact: Uncontrolled high-bandwidth UDP Flows can affect other network users’ traffic For this reason, e-VLBI uses control protocol to become a transparent user Experiment ran July 15, 2003 • RTCP in conjunction with RTP provides: • Mechanisms for reliably monitoring a networks’ real-time data delivery performance • Means to collect statistics from participants and distribute them to other participants • Ways to adapt transmission strategies to prevailing network conditions The future of e-VLBI • Many telescopes will be able to send date to many correlators • Data will not need to be stored of disks • Protocols developed can be used in other fields, outside e-VLBI RTP framing works!! Acronym Guide: RTP: Real-time Transport Protocol VLBI: Very-Long-Baseline Interferometry RTCP: RTP Control Protocol UDP: User Datagram Protocol

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