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Protocols DCCP and dccpmon.

Protocols DCCP and dccpmon. Richard Hughes-Jones The University of Manchester www.hep.man.ac.uk/~rich/ then “Talks”. UDPmon: The Measurements (1). Latency Round trip times measured using Request-Response UDP frames Latency as a function of frame size

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Protocols DCCP and dccpmon.

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  1. ProtocolsDCCP and dccpmon. Richard Hughes-Jones The University of Manchesterwww.hep.man.ac.uk/~rich/ then “Talks” ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester

  2. UDPmon: The Measurements (1) • Latency • Round trip times measured using Request-Response UDP frames • Latency as a function of frame size • Slope gives sum of individual data transfer rates end-to-end • Mem copy + pci + Gig Ethernet + pci + mem copy • Intercept indicates processing times + HW latencies • Histograms of ‘singleton’ measurements • Tells us about: • Behavior of the IP stack • The way the HW operates • Performance of the LAN / MAN / WAN ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester

  3. UDPmon: The Measurements (2) • UDP Throughput • Send a controlled stream of UDP frames spaced at regular intervals • Vary the frame size and the frame transmit spacing • At the receiver record • The time of first and last frames received • The number packets received, the number lost, number out of order • The received inter-packet spacing is histogramed • The time each packet is received  provides packet loss pattern • CPU load, Number of interrupts • Packets in/out on each interface • /proc/snmp IP and UDP counters • Use the CPU cycle counter for times and delay • Few lines of user code – fast & precise • Tells us about: • Behavior of the IP stack • The way the HW operates • Capacity and Available Throughput of the LAN / MAN / WAN ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester

  4. Zero stats / tsync OK done Send data frames at regular intervals Inter-packet time ●●● ●●● Time to receive Time to send Get remote statistics Send statistics Signal end of test OK done Number of packets n bytes  time Wait time UDPmon: The Works • How it works: • The ‘Zero_stats’ request also provides an interlock against concurrent tests. ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester

  5. DCCP: The Application View • Stephen & Richard with help from Andrea • Ported udpmon to dccpmon • Some system calls don’t work getsockopt(*soc, SOL_DCCP, DCCP_SOCKOPT_CHANGE_L, &dccp_features, &len); • Had problems with Fedora Core 6 using kernel 2.6.19-rc1 • DCCP data packets never reached the receiving TSAP ! • Verify with tcpdump • Using development “patches” kernel 2.6.19-rc5-g73fd2531-dirty • dccpmon tests • Plateau ~990 Mbit/s wire rate • No packet Loss • Receive system crashed! • Iperf tests • 940Mbps, back-to-back • Need more instrumentation in DCCP • Eg a line in /proc/sys/snmp ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester

  6. DCCP: Latest Kernel • Kernel 2.6.19_pktd-plus - ~2 weeks old • dccpmon tests • Receive system crashed even faster ! • Just 1 or 2 1000,000 packet tests • Iperf tests • OK short runs 940Mbps, back-to-back • Hangs longer runs ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester

  7. DCCP: dccpmon crash ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester

  8. DCCP: ccid-VLBI Discussion • Input from Haystack: Internet2 & Australia NRN view • Protect network from high bandwidth UDP flow • DoS Concerns • VLBI view • Want to send CBR data • Don’t want to drop throughput if just lost a packet due to error– tcpdelay results • DO want to know it there is congestion / packet loss • Don’t want SlowStart – DCCP RFC says use a ramp up phase • VLBI profile eg • Ack Ratio =10 • No Send Ack Vector ? • API ? ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester

  9. Any Questions? ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester

  10. Backup Slides ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester

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