IWSSC 2008 – Oct 3 rd 2008 Raffaello Secchi 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,

IWSSC 2008 – Oct 3 rd 2008 Raffaello Secchi Outline QoS in Satellite Networking –System Requirements –Architecture Components Scenarios and Results –Criteria for performance evaluation –Relevant cross-layer interactions Conclusions & Future work

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 IWSSC 2008 – Oct 3 rd 2008 Raffaello Secchi

IWSSC 2008 – Oct 3 rd 2008 Raffaello Secchi 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 providers 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

IWSSC 2008 – Oct 3 rd 2008 Raffaello Secchi 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 BoD, Framing 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

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 3 rd 2008 Raffaello Secchi

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

IWSSC 2008 – Oct 3 rd 2008 Raffaello Secchi SAL MAC IP L4 Segmentation (ULE) datasignalling Framing ATM, MPEG-2 flow control To/From NCC CR buffer monitoring DRA DVB-Frames TBTP User applications Transport (TFRC, TFRC-SP) Packet Scheduling Drop Tail, DRR, SFQ, CBQ Active Queue Management RED (Byte/Packet mode) Bandwidth on Demand RBDC, CRA VoIP packets Architecture Components Explicit/Implicit feedback Bandwidth/Delay tradeoffs Intra-flow & Inter- flow fairness

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 IWSSC 2008 – Oct 3 rd 2008 Raffaello Secchi

IWSSC 2008 – Oct 3 rd 2008 Raffaello Secchi 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

Effect of AQM and Packet scheduling IWSSC 2008 – Oct 3 rd 2008 Raffaello Secchi

Effects of Bandwidth on Demand IWSSC 2008 – Oct 3 rd 2008 Raffaello Secchi

IWSSC 2008 – Oct 3 rd 2008 Raffaello Secchi 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?