ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester1

Protocols

DCCP and dccpmon.

Richard Hughes-Jones The University of Manchester

www.hep.man.ac.uk/~rich/ then “Talks”

ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester2

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-endMem 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 Manchester3

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 Manchester4

UDPmon: The Works

How it works: The ‘Zero_stats’ request also provides an interlock against concurrent tests.

Zero stats / tsync OK done

●●●

Get remote statisticsSend statistics

Send data frames atregular intervals ●●●

Time to send Time to receive

Inter-packet time

Signal end of testOK done

n bytes

Number of packets

Wait timetime

ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester5

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

zeus15-atb79_29Sep06

0100200300400500600700800900

1000

0 10 20 30 40Spacing between frames us

Rec

v W

ire r

ate

Mbi

t/s

800 bytes

1000 bytes

1200 bytes

1400 bytes

1424 bytes

ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester6

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 Manchester7

DCCP: dccpmon crash

ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester8

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 =10No Send Ack Vector ?

API ?

ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester9

Any Questions?

ESLEA Bits&Bytes, Manchester, 7-8 Dec 2006, R. Hughes-Jones Manchester10

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