APOHN: Subnetwork Layering to Improve TCP Performance over Heterogeneous Paths

1. April 4, 2006 APOHN:Subnetwork Layering to Improve TCP Performance over Heterogeneous Paths Dzmitry Kliazovich, Fabrizio Granelli, University of Trento, Italy Giovanni Pau, Mario Gerla University of California, Los Angeles

2. Presentation Outline • TCP/IP in Heterogeneous Networks • APOHN Architecture • Techniques, Protocol, and Security • Performance Evaluation • In Satellite + Wireless LAN Network • Conclusions and Future Potential Dzmitry Kliazovich (klezovic@dit.unitn.it)

3. Background • Nowadays Networks (Heterogeneous) • TCP/IP protocol suite • Wireless, Satellite links • Terminal Mobility • Limited Bandwidth • Large Propagation Delays • Signal Fading • High Error Rates (10-3 – 10-1) • Designed in late 70s (ARPANET) • Strong Hierarchical structure • Static Routing • Stable Connectivity • Small Propagation Delays • Low Error Rates (BER: 10-8 – 10-6) Dzmitry Kliazovich (klezovic@dit.unitn.it)

4. TCP/IP Improvements • Modify TCP bringing desired behavior • Examples: TCP Westwood, TCP-DOOR, etc. • Drawbacks: Difficulty to maintain E2E semantics, requires modification of standardized and widely implemented TCP/IP stack Transparent Adaptation • Hide from TCP undesirable physical characteristics • Examples: ARQ and FEC at the link layer • Drawback: Not all the characteristics can be compensated in transparent way TCP Modification Dzmitry Kliazovich (klezovic@dit.unitn.it)

5. TCP/IP Semantics Connection Service for Applications Connect Network Nodes TCP TCP Connect Neighbor Nodes Network (IP) Network (IP) Link Link Physical Physical Dzmitry Kliazovich (klezovic@dit.unitn.it)

6. TCP TCP Network (IP) Network (IP) TCP/IP Semantics • Heterogeneous Network? Subnetwork Subnetwork Link Link Physical Physical Dzmitry Kliazovich (klezovic@dit.unitn.it)

7. APOHN Architecture Dzmitry Kliazovich (klezovic@dit.unitn.it)

8. APOHN Architecture • Optimize Subnetwork Communications • Subnetwork Protocols (SBP) • Split-Connection at Subnetwork Layer • Preserve End-to-end Transport Layer • No Changes for TCP/IP OS Implementation Dzmitry Kliazovich (klezovic@dit.unitn.it)

9. Protocol Booster • Buffer TCP packets • Control TCP with Receiver Advertise windows (rwnd) • E2E Reliability: keep a packet in buffer until it’s E2E acknowledged • Protocol Booster – Transparent interface between TCP and Subnetwork layers D. Feldmeier at el., “Protocol boosters,” IEEE JSAC, vol. 16, no. 3, pp. 437 – 444, 1998. Dzmitry Kliazovich (klezovic@dit.unitn.it)

10. Protocol Booster • Implemented at Sender Node • Protocol Booster completely disables TCP flow control mechanism without direct modifications on Transport layer • TCP becomes a controlled source of packet data Dzmitry Kliazovich (klezovic@dit.unitn.it)

11. Subnetwork Flow Multiplexing • Rate-based or Window-based flow control at Subnetwork layer • Results in TCP flow speed up: no need to probe the capacity with Additive Increase Multiplicative Decrease (AIMD) • Network Utilization Increase Dzmitry Kliazovich (klezovic@dit.unitn.it)

12. Related Works • Delay-Tolerant Network (DTN) • Overlay network • Adds Bundle layer above TCP • E-mail style communications • Drawbacks • Modifies TCP/IP • Requires dedicated (overlay) nodes • Router nodes process whole protocol stack • Can not handle delay sensitive traffic Dzmitry Kliazovich (klezovic@dit.unitn.it)

13. Related Works • Performance Enhancement Proxy (PEP) Dzmitry Kliazovich (klezovic@dit.unitn.it)

14. Related Works • Performance Enhancement Proxy (PEP) • Designed for links or Subnetworks where TCP/IP performs poor • Typically Satellite links • Commonly Split-Connection approach • End-to-end connection is split into two or more connections • Use Optimized (non-TCP/IP) Protocol over aProblematic Link • Drawbacks • End-to-end Semantics not prevented • Large Processing + Buffer Overhead • Inability to Handle IPSec Dzmitry Kliazovich (klezovic@dit.unitn.it)

15. Secure Communications • Split-Connection on Transport Layer (like PEP) can not support IPSec • Multilayer IP Security (by Zhang at el.) as an adaptation of IPSec for split-connection PEPs • Divide network in the number of Zones (Subnetworks) • Encrypt for every zone (not End-to-end) Dzmitry Kliazovich (klezovic@dit.unitn.it)

16. Secure Communications • APOHN IPSec Support • End-to-end IPSec (RFC 2401) • Additional Subnetwork Security (Optional) Dzmitry Kliazovich (klezovic@dit.unitn.it)

17. Performance Evaluation • Simulated network: Satellite + Wireless LAN • Distributed Communications with no fixed infrastructure • Disaster Recovery, Military Applications Dzmitry Kliazovich (klezovic@dit.unitn.it)

18. Performance Evaluation • APOHN Subnetwork Protocols • Satellite Transport Protocol (STP) over Satellite Link • LLE-TCP (ACK suppression) over WLAN Dzmitry Kliazovich (klezovic@dit.unitn.it)

19. Performance Evaluation • Ns-2 Simulation Scenario • Satellite Link: 20 Mb/s, 300 ms downstream; 6 Mb/s, 300 ms upstream • Wireless LAN Link: IEEE 802.11b (PHY – 11 Mb/s) Dzmitry Kliazovich (klezovic@dit.unitn.it)

20. Performance Evaluation • Single-Flow Scenario • TCP Reno SACK triggers multiple timeouts • SaTPEP is limited by WLAN bottleneck Dzmitry Kliazovich (klezovic@dit.unitn.it)

21. Performance Evaluation • Congestion Window Evolution Loss Detected with DupACKs Loss Not Detected, Timeout Dzmitry Kliazovich (klezovic@dit.unitn.it)

22. Performance Evaluation • Bottleneck Buffer Multiple Overflow Drops Dzmitry Kliazovich (klezovic@dit.unitn.it)

23. Performance Evaluation • Multi-Flow Scenario Dzmitry Kliazovich (klezovic@dit.unitn.it)

24. Performance Evaluation • Cumulative Throughput Dzmitry Kliazovich (klezovic@dit.unitn.it)

25. Conclusions and Future Work • Need for TCP/IP Adaptation to Heterogeneous Network Environment • APOHN Architecture adds Subnetwork Layer to the protocol stack • Optimized Subnetwork Protocols, Flow Multiplexing, and Protocol Speedup are keys for Performance enahncement • IPSec is Supported Dzmitry Kliazovich (klezovic@dit.unitn.it)

26. Thank you! Dzmitry Kliazovich (klezovic@dit.unitn.it)