1 / 10

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

hop
Download Presentation

Protocols DCCP and dccpmon.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related