Things You Can Do in Budapest During Summer Time Aleksandar Kuzmanovic Rice University & Ericsson Traffic Lab October 2001

Rice University & Ericsson Traffic Lab Budapest Buda-Pest –History –Architecture –Decadency… Ericsson Traffic Lab –Unix –Young people –Security

Rice University & Ericsson Traffic Lab People Ericsson Traffic Lab, Budapest –Andras Veres EMULab, The University of Melbourne –Attila Pasztor, Darryl Veitch Budapest University, Department of Physics –Gabor Simon, Gabor Vattay

Rice University & Ericsson Traffic Lab My Goals Modeling and reality?

Rice University & Ericsson Traffic Lab Active Probing Internal network inaccessible Poor understanding of origins of complex network dynamics Statistics is like the bikini… Goal: Estimate the sample path of cross-traffic

Rice University & Ericsson Traffic Lab Background Precise measurement infrastructure One way delay (sec) -> Packet departure time (sec) ->

Rice University & Ericsson Traffic Lab Probing Uncertainty Principle Should not allow queue to empty between probe packets Small T for accurate measurements –but probe traffic would disturb cross-traffic (and overflow bottleneck buffer!) Larger T leads to measurement uncertainties –queue could empty between probes

Rice University & Ericsson Traffic Lab Theory Lindley’s equation CT information imbedded in delay Ideal case: minimally backlogging condition [QK99]

Rice University & Ericsson Traffic Lab Design Space No time synchronization between end points $ Delay difference Non-intrusiveness Stability Time (sec) -> One way delay (sec) ->

Rice University & Ericsson Traffic Lab Probing scheme

Rice University & Ericsson Traffic Lab Aside… Experiments on LAN Time-sharing in Linux Time (sec) -> Inter-arrival time (sec) ->

Rice University & Ericsson Traffic Lab Traffic Lab – Experiment Setup Tcpdump, iperf (HTTP, TCP), sender, receiver…

Rice University & Ericsson Traffic Lab Routes Tech. University Budapest 6 nec2.ttt.bme.hu ( ) ms ms ms Columbia University, NY 16 bongo.comet.columbia.edu ( ) ms * ms University of Melbourne 23 potoroo.ee.mu.OZ.AU ( ) ms ms ms Houston, we have a problem… -> Time (sec) -> One way delay (sec) ->

Rice University & Ericsson Traffic Lab Wide Area vs. Metropolitan Area Network

Rice University & Ericsson Traffic Lab Cross Traffic Estimation Sample Path Differentiate delay, know C Cross traffic: from: Budapest to: NY iperf - 1 TCP Probing traffic from: Budapest to: Melbourne

Rice University & Ericsson Traffic Lab Cross Traffic Estimation Moving Average

Rice University & Ericsson Traffic Lab Signs Delay difference => two queues => two cases

Rice University & Ericsson Traffic Lab Wide Area Network revisited Differentiation btw. primary (256K) & secondary (transatlantic) bottlenecks Secondary traffic underestimated for Csec./256K

Rice University & Ericsson Traffic Lab Primary & Secondary Bottlenecks LAN traffic controllable Separation between primary (256K) & secondary (LAN) cross traffic

Rice University & Ericsson Traffic Lab TCP Cross Traffic Iperf (number of TCP connections >=3) => delay decreases yet we see clusters of packet losses (queue size ~ delay~pck. loss?)

Rice University & Ericsson Traffic Lab Role of packet sizes => change packet size

Rice University & Ericsson Traffic Lab Bit/sec. vs. Packet/sec. Up: 540 Bytes Down: 60 Bytes 540/60 = 9 –256Kbps*9= 2.3Mbps UDP: 1500/30=50 –256K*50= 12.8Mbps - 1.5M*50= 75Mbps

Rice University & Ericsson Traffic Lab Secondary Bottleneck Difference of CT estimate and tcpdump CT followed by clusters of packet losses

Rice University & Ericsson Traffic Lab Role of TCP Secondary CT (necessary for losses*) picks up the periodicity of probe traffic! –Through losses –Through delay When phases match –Long burst of small packets causes losses on secondary bottleneck

Rice University & Ericsson Traffic Lab Ongoing work Short and long lived TCP connections Heterogeneous TCP traffic…

Rice University & Ericsson Traffic Lab Conclusions Scalable, edge-based tool for on-line network analysis, modeling, and measurement Scheme for estimating sample path of adaptive cross-traffic Differentiation between primary and secondary bottlenecks: two queue model Role of TCP (delay variation) and variable packet sizes –Low bit rate denial of service attack? –QoS in access networks (xDSL…)

Rice University & Ericsson Traffic Lab The End

Rice University & Ericsson Traffic Lab One more picture