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

Dzmitry Kliazovich April 4, 2006 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 April 4, 2006 Background TCP/IP protocol suite Nowadays Networks (Heterogeneous)  Designed in late 70s (ARPANET)  Strong Hierarchical structure  Static Routing  Stable Connectivity  Small Propagation Delays  Low Error Rates (BER: – )  Wireless, Satellite links  Terminal Mobility  Limited Bandwidth  Large Propagation Delays  Signal Fading  High Error Rates (10 -3 – )

Dzmitry Kliazovich April 4, 2006 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 TCP Modification  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

Dzmitry Kliazovich April 4, 2006 TCP/IP Semantics Physical Link Network (IP) TCP Connect Neighbor Nodes Connect Network Nodes Connection Service for Applications

Dzmitry Kliazovich April 4, 2006 TCP/IP Semantics Heterogeneous Network? Physical Link Network (IP) TCP Subnetwork

Dzmitry Kliazovich April 4, 2006 APOHN Architecture

Dzmitry Kliazovich April 4, 2006 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 April 4, 2006 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 April 4, 2006 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 April 4, 2006 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 April 4, 2006 Related Works Delay-Tolerant Network (DTN)  Overlay network  Adds Bundle layer above TCP  style communications Drawbacks  Modifies TCP/IP  Requires dedicated (overlay) nodes  Router nodes process whole protocol stack  Can not handle delay sensitive traffic

Dzmitry Kliazovich April 4, 2006 Related Works Performance Enhancement Proxy (PEP)

Dzmitry Kliazovich April 4, 2006 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 a Problematic Link Drawbacks  End-to-end Semantics not prevented  Large Processing + Buffer Overhead  Inability to Handle IPSec

Dzmitry Kliazovich April 4, 2006 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 April 4, 2006 Secure Communications APOHN IPSec Support  End-to-end IPSec (RFC 2401)  Additional Subnetwork Security (Optional)

Dzmitry Kliazovich April 4, 2006 Performance Evaluation Simulated network: Satellite + Wireless LAN  Distributed Communications with no fixed infrastructure  Disaster Recovery, Military Applications

Dzmitry Kliazovich April 4, 2006 Performance Evaluation APOHN Subnetwork Protocols  Satellite Transport Protocol (STP) over Satellite Link  LLE-TCP (ACK suppression) over WLAN

Dzmitry Kliazovich April 4, 2006 Performance Evaluation Ns-2 Simulation Scenario  Satellite Link: 20 Mb/s, 300 ms downstream; 6 Mb/s, 300 ms upstream  Wireless LAN Link: IEEE b (PHY – 11 Mb/s)

Dzmitry Kliazovich April 4, 2006 Performance Evaluation Single-Flow Scenario  TCP Reno SACK triggers multiple timeouts  SaTPEP is limited by WLAN bottleneck

Dzmitry Kliazovich April 4, 2006 Performance Evaluation Congestion Window Evolution Loss Detected with DupACKs Loss Not Detected, Timeout

Dzmitry Kliazovich April 4, 2006 Performance Evaluation Bottleneck Buffer Multiple Overflow Drops

Dzmitry Kliazovich April 4, 2006 Performance Evaluation Multi-Flow Scenario

Dzmitry Kliazovich April 4, 2006 Performance Evaluation Cumulative Throughput

Dzmitry Kliazovich April 4, 2006 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 April 4, 2006 Thank you!