Scheduling TCP-Friendly Flows over a Satellite Network

1. Scheduling TCP-Friendly Flows over a Satellite Network R. Secchi, A. Sathiaseelan, and G. Fairhurst Electronics Research Group University of Aberdeen Aberdeen, United Kingdom {raffaello, arjuna, gorry}@erg.abdn.ac.uk Raffaello Secchi

2. Outline • QoS in Satellite Networking • System Requirements • Architecture Components • Scenarios and Results • Criteria for performance evaluation • Relevant cross-layer interactions • Conclusions & Future work Raffaello Secchi

3. QoS in Satellite Networks • Features & goals of the global Internet • Universal Interconnection • Decentralization • Heterogeneous Networking • Multiservice & IP oriented • Objectives of QoS-Sat management • Integration in a large-scale network • Support of a wide range of applications Raffaello Secchi

4. Approaches to QoS provisioning • Limitations of hard QoS approaches (IntServ) • Traffic must be classified • A layer-3 to layer-2 mapping is required • Lack of network policies standardization: the end-to-end behavior is difficult to guarantee • Subjectivity of policies: one provider’s gold traffic can be bronze for another • The capacity argument • End-to-end QoS schemes • High service levels under normal traffic conditions • Preventing collapse under high traffic loads Raffaello Secchi

5. System Requirements • A transport framework able to support multimedia applications • Satisfying multimedia QoS requirements • Compatibility with existing TCP services • Network stability DCCP AQM, Fair queuing • Active participation of IP layer • Fast feedback to upper-layer congestion control • Flow isolation & intelligent scheduling • Effective use of satellite capacity • TCP/IP oriented design • Tuning knobs for efficiency vs. performance tradeoffs • Appropriate burst assignment across long superframes BoD, Framing Raffaello Secchi

6. DCCP: The State of Art • DCCP provides a framework for congestion control for multimedia flows • RFC 5348 (TFRC) proposed standard • Suited for streaming media • Rate-based protocol • Requires sender and receiver participation • Periodic feedback reports • Smoothly variable sending rate • RFC 4828 (TFRC-SP) • Small packet variant of TFRC • Suited for VoIP IWSSC 2008 – Oct 3rd 2008 Raffaello Secchi

7. TFRC development process 2008 2000 2007 future 2006 RFC 5348 RFC 4342 RFC 4828 RFC 3448 Revision of TFTC TFRC-SP variant CCID3 in DCCP • Expanding TFRC framework (new CCID?) • TFRC-SP in DCCP framework TFRC specifications IWSSC 2008 – Oct 3rd 2008 Raffaello Secchi

8. Architecture Components User applications VoIP packets Explicit/Implicit feedback L4 Transport (TFRC, TFRC-SP) Active Queue Management RED (Byte/Packet mode) Intra-flow & Inter-flow fairness buffer monitoring IP Packet Scheduling Drop Tail, DRR, SFQ, CBQ flow control SAL Segmentation (ULE) Bandwidth/Delay tradeoffs data signalling MAC Bandwidth on Demand RBDC, CRA CR Framing ATM, MPEG-2 TBTP To/From NCC DRA DVB-Frames Raffaello Secchi

9. Simulation methodology • Simulation scenario • Individual terminal scenario • MF-TDMA over return link • TDM over forward link • Algorithms considered • DCCP: TFRC, TFRC-SP • AQM: RED byte/packet mode • IP layer: DropTail, DRR, SFQ, Prio • BoD: RCDC, CRA • Evaluation Criteria • R-score (objective quality estimation) • Max-min fairness Raffaello Secchi

10. Effects of flow isolation on TFRC • A single TFRC streaming application may not achieve fairness when sharing with multiple data TCP flows • DRR is able to restore fairness and improve performance Raffaello Secchi

11. Effect of AQM and Packet scheduling Raffaello Secchi

12. Effects of Bandwidth on Demand Raffaello Secchi

13. Conclusions • The soft QoS concept for satellite networks • Architecture definition and its purpose • Identifying main elements, their scope and cross-layer interactions • Strong points and weaknesses • Ideas for the future research • Parametric optimization of arch. elements • Towards an emulative testbed? Raffaello Secchi