1. PSMC Proxy Server-based Multipath Connection CS 526 Advanced Networking - Richard White

2. Overview Network Architectures Network Overlays SCOLD PSMC Issues Conclusion On Proxy Server Based Multipath Connections Yu Cai, PhD Dissertation, UCCS, 2005

3. Network Architecture Clients Servers Routers Links Name Servers

4. Client/Server Model 1. Client requests DNS name translaton 2. Router directs query to local proxy server 3. Proxy server redirects shortest path to host

5. Client/Server Problems 1. Client requests DNS name translation 2. Router directs query to local proxy server 3. Proxy server redirects shortest path to host Shortest path not always fastest! Wasted bandwidth!

6. Client/Server Vulnerability 1. Client requests DNS name translation 2. Router directs query to local proxy server 3. Proxy server redirects shortest path to host Shortest path not always fastest! Wasted bandwidth! Distributed Denial of Service (DDoS) Attack!

7. Layered Architecture

8. Service Overlays Build on existing capabilities Don’t need to retrofit existing services Modular compatibility for adding and removing

9. Secure Collective Defense (SCOLD) SCOLD Coordinator SCOLD Proxy Servers

10. Secure Collective Defense (SCOLD) SCOLD Coordinator SCOLD Proxy Servers Defends against DDoS attacks!

11. Secure Collective Defense (SCOLD) SCOLD Coordinator blocks incoming attack on main gateway Notifies trusted DNSs to use trusted proxys Trusted proxys route requests through alternate gateways

12. SCOLD Performance SCOLD overhead incurs performance delays SCOLD overhead is insignicant compared to attacks!

13. Proxy Server-based Multipath Connection (PSMC) Can we extend the SCOLD concept to enhance network perfromance? Shortest path not always fastest! Wasted bandwidth!

14. PSMC Architecture Sender module responsible for packet distribution among multiple paths Some packets go through normal “direct route” Some packets go through “indirect routes” Receiver module reassembles packets in correct order.

15. Proxy Server-based Multipath Connection (PSMC) Aggregating bandwidth increases throughput Multiple paths increase reliability, decrease vulnerability

16. 123456 Proxy Server-based Multipath Connection (PSMC) PSMC increases probability packets arrive out of order 12345612564312

17. 123456 Proxy Server-based Multipath Connection (PSMC) PSMC increases probability packets arrive out of order 123456125643 Resulting in significantly higher retransmit requests 5643

18. 123456 Buffer 2 Buffer 1 125643123456 Proxy Server-based Multipath Connection (PSMC) 123456125643 PSMC increases probability packets arrive out of order Resulting in significantly higher retransmit requests Solution: Create a double receiving buffer!

19. PSMC Performance PSMC without double buffering was worse than standard routing! PSMC with double buffering was significantly better than standard routing!

20. Issues Detecting compromised proxy servers Controlling malicious users More efficient double- buffer management Investigating quality of service capabilities

21. Conclusion Increase bandwidth utilization Decrease vulnerability to attack & failure Can be used to implement quality of service proportional differentiation