1. SProbe: Another Tool for Measuring Bottleneck Link Bandwidth Stefan Saroiu P. Krishna Gummadi Steven Gribble University of Washington

2. Peer-to-Peer File-Sharing Systems Ongoing project - analyze and measure characteristics of current P2P systems Estimate bottleneck bandwidths to and from many and diverse Internet hosts: –Traditional modems: ppp35.bcpl.net –Cable modems: c589502-a.plano1.tx.home.com –DSL: adsl-78-148-152.cae.bellsouth.net –Dorms (10/100 Mbps): st14_032.dorm.depaul.edu

3. Wanted: Sexy Linux Tool that: 1.Measures a network physical property - bottleneck bandwidths 2.Has reasonable accuracy Willing to tolerate factor-of-two errors 3.Preferably returns only one estimate 4.Runs fast 1 min/host is too slow 5.Measurement software is deployed at only one endpoint

4. Problems with Contenders Measuring ALL links bandwidths is slow: –pathchar, pchar, clink Measurement software must be deployed at both endpoints: –pathrate Estimates based on ICMP: –ICMP can be filtered, dropped, answered by routers, rate-limited answers –bprobe

5. Problems with Contenders (2) Estimates based on passively monitoring traffic to and from the remote host: –This works as long as the traffic is formed by large packets-pairs –Unfortunately, most of our traffic is not –nettimer Traffic is processed as a set of packet- pairs only: –Traffic can be shaped to reveal more information – cross-traffic detection

6. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

7. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

8. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

9. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

10. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

11. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

12. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

13. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

14. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

15. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

16. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

17. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

18. SProbe Uses TCP Tricks From local host To remote host –No cooperation needed LocalRemote SYN packet RST packet

19. SProbe Uses TCP Tricks From remote To local –Involuntary cooperation of application layer LocalRemote (Web) HTTP Get request Data packet ACK (last data packet)

20. Trials (local to remote) SProbe sends train of 6 packets (3160 bytes/train), upto 10 times

21. Trials (local to remote) SProbe sends train of 6 packets (3160 bytes/train), upto 10 times

22. Trials (local to remote) SProbe sends train of 6 packets (3160 bytes/train), upto 10 times

23. Trials (local to remote) SProbe sends train of 6 packets (3160 bytes/train), upto 10 times

24. Final Remarks A useful tool (for us) needs to: –Be deployed at one endpoint only –Run fast –Actively send probing packets –Detect cross-traffic interference When cross-traffic detected return ‘Unknown Estimate’ Do not returns bogus estimate instead, please. SProbe source will be available shortly: –http://www.cs.washington.edu/homes/tzoompy/sprobe