1. The First Implementation of RTP Framing for e-VLBI
Amanda Morrow
David Lapsley
Alan Whitney
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.
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