1. Advanced Computer Networks SPEP: A Secure and Efficient Scheme for Bulk Data Transfer over Wireless Networks Venkatesh Obanaik, Lillykutty Jacob, and A L Ananda Communication and Internet Research Lab National University of Singapore Presented by Mark Johnson

2. Advanced Computer Networks Introduction Enhance performance in a wired/wireless environment Be able to enhance performance while maintaining end-to-end security Minimize overhead introduced

3. Advanced Computer Networks Previous Approaches: Performance Enhancement Split Connection approaches (I-TCP, MTCP) –Violate end-to-end semantics and prevent use of end-to- end IPSEC End-to-End approaches (SNOOP, M-TCP, WTCP, ELN) –Assume TCP headers are readable TCP HACK –Inherently won’t work due to the fact that IPSEC integrity check will discard corrupted packets

4. Advanced Computer Networks Previous Approaches: Performance Enhancement Freeze-TCP –Will work with end-to-end IPSEC –Only provides a solution for disconnection issues, doesn’t distinguish congestion from corruption Delayed Duplicate Acknowledgement –Open issues regarding differentiation of packet loss nature

5. Advanced Computer Networks Previous Approaches: Security Intelligent PEP switch –Can choose between security and performance, can’t have both SSL –Encrypts data and still works with performance enhancement –Doesn’t encrypt TCP headers TF-ESP –Forces authentication of TCP header information but still exposes too much information

6. Advanced Computer Networks SPEP Approach Loss Detection –Running sequence number for all packets sent –Base station keeps track of packets received in sequence –Receiver checks base station information vs. received packet information to determine whether loss is due to congestion or corruption –All detection is done one-way from sender to receiver

7. Advanced Computer Networks SPEP Approach

8. Advanced Computer Networks SPEP Approach Recovery –Set a bit in TCP header of duplicate ACK –Sender retransmits corruption losses without invoking congestion control mechanisms

9. Advanced Computer Networks Implementation Considerations Uses IPv6 implementation –Flow label and source address allow SPEP to uniquely identify flows –ESP header contains counter –DSTOPT header can be used to carry blocks of in-sequence numbers

10. Advanced Computer Networks Test Configuration

11. Advanced Computer Networks Performance Evaluation: LAN

12. Advanced Computer Networks Performance Evaluation: WAN

13. Advanced Computer Networks Performance Evaluation: Throughput

14. Advanced Computer Networks SPEP Merits Provides end-to-end service Only tracks packets in forward direction Smooth handoff; minimal state information Easily Scalable Can be used as a generic network layer proxy