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Passive Duplicate Address Detection (DAD)

Passive Duplicate Address Detection (DAD). Sangho Shin Andrea Forte Henning Schulzrinne Columbia University. Motivation (1/2). AR (Access Router). AR. Layer 2 handoff. Subnet change. Layer 3 handoff. New IP acquisition. Session update. Layer 3 (IP Layer) Handoff. Motivation (2/2).

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Passive Duplicate Address Detection (DAD)

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  1. Passive Duplicate Address Detection (DAD) Sangho Shin Andrea Forte Henning Schulzrinne Columbia University

  2. Motivation (1/2) AR (Access Router) AR Layer 2 handoff Subnet change Layer 3 handoff New IP acquisition Session update Layer 3 (IP Layer) Handoff

  3. Motivation (2/2) • Standard DHCP procedure (RFC2131) DHCP server DHCP DISCOVER Pick an unassigned IP (Broadcast) Performs Duplicate Address Detection (DAD) - Send ICMP ECHO to the IP Wait for the response for 1 second DHCP OFFER DHCP REQUEST DHCP ACK

  4. Problems of the current DAD • Long waiting time • Long ICMP response time in congested wireless network • ISC DHCP server – 1 sec • 1 second waiting time is critical for real time services • Unreliable • Windows XP SP2 Firewall • Block ICMP echo by default • Most of the windows machines do not respond to ICMP echo • Possible packet loss in wireless networks

  5. Monitor traffic constantly 160.123.234.31 160.123.231.32 160.123.235.35 160.123.232.36 160.123.238.38 Collect IP usage V 160.123.234.31 V Update IP table 160.123.234.32 V 160.123.234.35 V 160.123.234.36 160.123.234.31 160.123.234.38 No explicit DAD Basic Concept Request Response

  6. Architecture (1/2) DHCP server Address Usage Collector (AUC) router subnet switch

  7. Architecture (2/2) DHCP server AUC AUC RA Relay Agent (RA)

  8. 1.1.1.1 AA-BB-CC 1.1.1.1 AA-BB-CC 100 Example 1 • IP address collection DHCP server IP MAC Expire AUC Lease table IP:1.1.1.1 MAC:AA-BB-CC IP MAC Web server Router ARP query IP:1.1.1.1 IP:1.1.1.1 MAC:AA-BB-CC

  9. 1.1.1.1 1.1.1.2 DD-EE-FF AA-BB-CC 1.1.1.2 1.1.1.1 DD-EE-FF AA-BB-CC 100 100 Example 2 • Malicious user detection DHCP server IP MAC Expire AUC Lease table IP:1.1.1.2 MAC:DD-EE-FF IP MAC Web server Bad IP table IP MAC Router ARP query IP:1.1.1.1 MAC:AA-BB-CC IP:1.1.1.2 MAC:DD-EE-FF

  10. 1.1.1.1 1.1.1.2 1.1.1.1 AA-BB-CC AA-BB-CC DD-EE-FF 1.1.1.1 1.1.1.2 1.1.1.1 AA-BB-CC AA-BB-CC DD-EE-FF 100 100 100 Example 3 • IP collision detection DHCP server IP MAC Expire AUC Lease table IP:1.1.1.1 MAC:00-00-00 IP MAC Web server Bad IP table IP MAC Router Block 00-00-00 Forward HTTP traffic FORCE RENEW IP:1.1.1.3 ARP query IP:1.1.1.1 MAC:AA-BB-CC IP:1.1.1.2 IP:1.1.1.1 MAC:DD-EE-FF MAC:00-00-00

  11. Experiments Columbia WLAN DHCP Server AUC Columbia CS network

  12. Experimental results (1/4) • Convergence time

  13. Experimental results (2/4) • DHCP server traffic load from AUC

  14. Experimental results (3/4) • AUC traffic load (ARP and broadcast)

  15. Experimental results (4/4) • CPU load of AUC

  16. Conclusions • It takes time to acquire an IP from DHCP server mostly because of DAD – 1 sec • The current DAD does not work because of Windows XP SP2 • Passive DAD performs DAD with no overhead • Passive DAD detectsIP address collision and illegally used IPs • When a address collision is detected, Passive DAD resolves the duplicate IP problem by using DHCP Force Renew

  17. Thank you!

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