NRAO – Westford e-VLBI Trial

1. NRAO – Westford e-VLBI Trial Chester Ruszczyk / Walter Brisken MIT Haystack / NRAO U.S. VLBI Technical Coordination Meeting, Socorro NM

2. Agenda • Trial Description • Trial Results • Network Performance • Steps To Achieve Success • May 21st Trial • Others ? U.S. VLBI Technical Coordination Meeting, Socorro NM

3. Trial Description • Real-time e-VLBI Trial • May 7th 12 UTC – 16 UTC • X band • Antennas • VLA single dish • Westford • Correlator • Haystack • Mode • 32 Mbps single channel U.S. VLBI Technical Coordination Meeting, Socorro NM

4. U.S. VLBI Technical Coordination Meeting, Socorro NM

5. Trial Results • Auto-correlation • Westford • Failed to get auto-correlation with VLA • Issue was network performance • Socorro to Haystack • No fringes were attempted to be detected U.S. VLBI Technical Coordination Meeting, Socorro NM

6. Network Performance • Link from Socorro to NYC • ~42Mbps • Link from Socorro to Haystack • 32.7 Mbps MAX. • Drops in performance on the sending machine • Failed to maintain required data rate • ~34Mbps U.S. VLBI Technical Coordination Meeting, Socorro NM

7. Network Performance • Potential source of the performance failure • Backbone between NYC - Haystack • Rate limiting Socorro and Albuquerque • 35Mbps maximum • May be limiting TCP performance for long haul networks • Investigating U.S. VLBI Technical Coordination Meeting, Socorro NM

8. Next Steps • Isolate the network performance between the backbone and the end systems. • Quantify the performance from the Mark5A at the VLA to Haystack • This can be a noise source being sent from the VLA to Haystack and decoded at the correlator • Implementing Web100 based kernel to analyze the end-systems • Determine why 42Mbps was achievable between VLA and NYC but not beyond. • Verify Performance from • Denver, Chicago, NYC to Haystack U.S. VLBI Technical Coordination Meeting, Socorro NM

9. Next Steps (cont) • Install Network Diagnostic tools on Mk5s • Quantify end systems and • end-to-end characteristics • If we are unable to sustain the required TCP traffic through testing • Use constant bit rate UDP based protocol • May 21, attempt the second test. • VLA network connection extended beyond May. • Other test dates? U.S. VLBI Technical Coordination Meeting, Socorro NM