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Networking for ATLAS Remote Farms

This document summarizes the networking performance tests conducted on the GÉANT Core, focusing on end-to-end measurements relevant to the ATLAS Remote Farms project. Key aspects include UDP throughput evaluation, packet loss analysis, and TCP stack performance under various conditions. Tests were carried out between major GEANT Points of Presence, addressing reordering, jitter, one-way delay, and recovery times of different TCP configurations. The findings from these tests are essential for improving data transfer efficiency in high-performance computing environments.

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Networking for ATLAS Remote Farms

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  1. Networking for ATLAS Remote Farms Richard Hughes-Jones The University of Manchester DataGrid WP7 – Dante Tests on the GÉANT Core End-2-End Measurements from the 4th Year VLBI Project at Manchester New TCP stacks – the effect on throughput Some Simple Network Tests CERN-Manchester Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  2. DataGrid WP7 – Dante Tests on the GÉANT Core • Set-up • Supermicro PC in: • London GEANT PoP • Amsterdam GEANT PoP • Smartbits in: • London GEANT PoP • Frankfurt GEANT PoP • Long link UK-SE-DE2-IT-CH-FR-BE-NL • Short Link UK-FR-BE-NL Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  3. Tests GÉANT Core: UDP throughput • UDP Throughput • London-Amsterdam • Available BW to packet on wire • Then 1/t • Wire rate 998 Mbit/s for packets > 1400 bytes • Packet Loss • None for large packets • Dips in BW lined to packet loss • SysKonnect NIC int. per packet • CPU load important Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  4. Tests GÉANT Core: Packet re-ordering • Effect of Packet size • London-Amsterdam • Packets at 10 µs – line speed • 10,000 sent • Packet Loss ~ 0.1% • Re-order Distribution Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  5. Tests GÉANT Core: Packet re-ordering • Effect of LBE background • Amsterdam-London • BE Test flow • Packets at 10 µs – line speed • 10,000 sent • Packet Loss ~ 0.1% • Re-order Distributions: Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  6. Tests GÉANT Core: Packet Jitter • Amsterdam-London • BE Test flow • Packet spacing 80 µs • BE Test flow + Background: 60% BE 1.4Gbit + 40% LBE 780Mbit • IPPremium Test flow + Background • IPPremium Test flow Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  7. Tests GÉANT Core: 1-way Delay • Amsterdam-London • IPPremium Test flow • Packet spacing 80 µs • BE Test flow + Background: 60% BE 1.4Gbit + 40% LBE 780Mbit • BE Test flow + Background: 60% BE 1.4Gbit + 40% LBE 780Mbit Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  8. VLBI Project: Test Topology SURFnet Manchester JIVE Dwingaloo Jodrell SuperJANET4 Adam Mathews Steve O’Toole Univ of Manchester Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  9. VLBI Project: Throughput • Manchester to Dwingeloo • 2.0G Hz Xeon 1.2 GHz PIII • Re-ordering vs Offered Load Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  10. 1-way Delay – note the packet loss (points with 0 –way delay) VLBI Project: Jitter & 1-way Delay • 1472 byte Packets man -> JIVE • FWHM 22 µs (B2B 3 µs ) Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  11. VLBI Project: Packet Loss – Long Range Effects? • Aggregated Variance Method • Divide time series length N into blocks of size m • Calc mean of each section Xm(k) k= 1 … N/m • Calc variance VXm of these Xm(k) • Vary m size of the blocks • Plot on log-log & fit slope β • Hurst parameter Hβ = 2H -2 • Measure:β = -0.355 which gives H 0.822 • H =1 no long range dependence Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  12. Traffic Flows • Manchester – NetNorthWest - SuperJANET Access links • Two 1 Gbit/s • Access links:SJ4 to GÉANT GÉANT to SurfNet Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  13. High Performance TCP – DataTAG • Different TCP stacks tested on the DataTAG Network • 128 ms round trip time • Drop 1 in 106 • High-Speed • Rapid recovery • Scalable • Very fast recovery • Standard • Recovery would take ~ 10 mins Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  14. MB-NG Managed Bandwidth High Performance TCP – MB-NG • Drop 1 in 25,000 • Rtt 6.2 ms • Recover in 1.6 s Standard HighSpeed Scalable Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  15. Zero stats OK done Request event Send event data Request-Response time (Histogram) ●●● ●●● Get remote statistics Send statistics: CPU load & no. int 1-way delay Some Network Tests • TCP Request – Response Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  16. Lab Test: TCP Request-Response Histograms • PC – router – PC • BE Test flow • Request spacing 0 µs • Request spacing 10 ms Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  17. Man-CERN: TCP Request-Response Latency • DataTAG PC – backup link • BE Tests • Request spacing 0 µs • Win size 2.5Mbytes • Compare with UDP latency • Large differences • Rtt of 20 msdelay*bw = 2.5 Mbytes • 1Mbyte data = 690 pkts  interesting bursts ! Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  18. Man-CERN: UDP Throughput & Packet Loss • DataTAG PC – backup link • BE Tests • Throughput • Packet loss Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  19. Traffic Flows • Manchester – NetNorthWest - SuperJANET Access links • Link to PC in M/c • Access links: • 1 GE Man to NNW • Total Man to NNW • NNW to SuperJANET4 Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  20. Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  21. VLBI Project: Packet Loss – Is it Poisson? • Divide time series of packets into 1000 slices of 50 packets • Total lost packets 1410 • Average number / slice = 1.4 • Calc Poisson ProbabilityP(n, µ) = µ n e -µ n! • Curves close but not exact • Could be more than 1 process Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  22. Traffic QoS Classes on GÉANT Backbone Max Throughput on 2.5 G PoS • Normal Traffic + • Radio Astronomy Data + • Less Than Best Effort • 2.0 Gbit/s • Normal Traffic + • Less Than Best Effort • 2.0 Gbit/s • Normal Traffic + • Radio Astronomy Data • 500 Mbit/s • Normal Traffic Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

  23. Some Measurements made during ER2002 Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004 R. Hughes-Jones Manchester

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