A Resource and Energy Efficient Network for IPTV
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UCAM-CL-TR-826 Technical Report ISSN 1476-2986 Number 826 Computer Laboratory GREEN IPTV: a resource and energy efficient network for IPTV Fernando M. V. Ramos December 2012 15 JJ Thomson Avenue Cambridge CB3 0FD United Kingdom phone +44 1223 763500 http://www.cl.cam.ac.uk/ c 2012 Fernando M. V. Ramos This technical report is based on a dissertation submitted November 2012 by the author for the degree of Doctor of Philosophy to the University of Cambridge, Clare Hall. Technical reports published by the University of Cambridge Computer Laboratory are freely available via the Internet: http://www.cl.cam.ac.uk/techreports/ ISSN 1476-2986 GREEN IPTV: A Resource and Energy Efficient Network for IPTV Fernando M. V. Ramos Abstract The distribution of television is currently dominated by three technologies: over- the-air broadcast, cable, and satellite. The advent of IP networks and the increased availability of broadband access created a new vehicle for the distribution of TV services. The distribution of digital TV services over IP networks, or IPTV, offers carriers flexibility and added value in the form of additional services. It causes therefore no surprise the rapid roll-out of IPTV services by operators worldwide in the past few years. IPTV distribution imposes stringent requirements on both performance and relia- bility. It is therefore challenging for an IPTV operator to guarantee the quality of experience expected by its users, and doing so in an efficient manner. In this dis- sertation I investigate some of the challenges faced by IPTV distribution network operators, and I propose novel techniques to address these challenges. First, I address one of the major concerns of IPTV network deployment: channel change delay. This is the latency experienced by users when switching between TV channels. Synchronisation and buffering of video streams can cause channel change delays of several seconds. I perform an empirical analysis of a particular solution to the channel change delay problem, namely, predictive pre-joining of TV channels. In this scheme each Set Top Box simultaneously joins additional multicast groups (TV channels) along with the one requested by the user. If the user switches to any of these channels next, switching latency is virtually eliminated, and user experience is improved. The results show that it is possible to eliminate zapping delay for a significant percentage of channel switching requests with little impact in access network bandwidth cost. Second, I propose a technique to increase the resource and energy efficiency of IPTV networks. This technique is based on a simple paradigm: avoiding waste. To reduce the inefficiencies of current static multicast distribution schemes, I propose a semi- dynamic scheme where only a selection of TV multicast groups is distributed in the network, instead of all. I perform an empirical evaluation of this method and conclude that its use results in significant bandwidth reductions without compromising service performance. I also demonstrate that these reductions may translate into significant energy savings in the future. Third, to increase energy efficiency further I propose a novel energy and resource friendly protocol for core optical IPTV networks. The idea is for popular IPTV traffic to optically bypass the network nodes, avoiding electronic processing. I evaluate this proposal empirically and conclude that the introduction of optical switching techniques results in a significant increase in the energy efficiency of IPTV networks. All the schemes I present in this dissertation are evaluated by means of trace-driven analyses using a dataset from an operational IPTV service provider. Such thorough and realistic evaluation enables the assessment of the proposed techniques with an increased level of confidence, and is therefore a strength of this dissertation. List of publications In the course of my studies I have published the papers and technical reports presented below. Some papers discuss topics covered in this thesis, while others describe distinct research threads. The paper \Channel Smurfing: Minimising Channel Switching Delay in IPTV Distribution Net- works" has been given a best paper award. [2012] H. Kim, J. Crowcroft, and F. M. V. Ramos. Efficient channel selection using hierarchical clustering. In WoWMoM, San Francisco, CA, June 2012. [2011] F. M. V. Ramos, J. Crowcroft, R. J. Gibbens, P. Rodriguez, and I. H. White. Reducing channel change delay in IPTV by predictive pre-Joining of TV Channels. Signal Processing: Image Communication, 26(7):400412, 2011. [2010] F. M. V. Ramos, R. J. Gibbens, F. Song, P. Rodriguez, J. Crowcroft, and I. H. White. Reducing energy consumption in IPTV networks by selective pre-joining of channels. In SIGCOMM workshop on green networking, New Delhi, India, Aug. 2010. [2010] F. M. V. Ramos, J. Crowcroft, R. J. Gibbens, P. Rodriguez, and I. H. White. Channel smurfing: Minimising channel switching delay in IPTV distribution networks. In ICME, Singapore, July 2010. [2010] F. Song, H. Zhang, S. Zhang, F. M. V. Ramos, and J. Crowcroft. Relative delay estimator for SCTP-based Concurrent Multipath Transfer. In GLOBECOM, Miami, FL, Dec. 2010. [2009] F. M. V. Ramos, F. Song, P. Rodriguez, R. Gibbens, J. Crowcroft, and I. H. White. Constructing an IPTV workload model. In SIGCOMM poster session, Barcelona, Spain, Aug. 2009. [2009] F. M. V. Ramos, A. Giorgetti, F. Cugini, P. Castoldi, J. Crowcroft, and I. H. White. Power excursion aware routing in GMPLS-based WSONs. In OFC, San Diego, CA, Mar. 2009. [2009] F. Song, H. Zhangy, S. Zhangy, F. M. V. Ramos, and J. Crowcroft. Relative delay estimator for multipath transport. In CoNEXT Student Workshop, Rome, Italy, Dec. 2009. [2009] F. Song, H. Zhang, S. Zhang, F. Ramos, and J. Crowcroft. An estimator of forward and backward delay for multipath transport. Computer Laboratory Technical Report UCAM- CL-TR-747, March 2009. [2008] F. Ramos. Design of a GMPLS system for provisioning optical core and access networks for multicast TV. In Eurosys doctoral workshop, Glasgow, UK, Mar. 2008. Contents Contents 7 List of Figures 11 List of Tables 13 Glossary 15 1 Introduction 19 1.1 What is IPTV? . 19 1.2 Motivation . 20 1.2.1 The Value of IPTV . 20 1.2.2 Killer application? . 20 1.2.3 Challenges . 21 1.3 Issues not covered in this thesis . 22 1.3.1 IPTV, not Internet TV nor P2P TV . 22 1.3.2 Broadcast IPTV, not VoD . 22 1.3.3 Single-domain IPTV, not multiple . 22 1.4 Contributions . 22 1.4.1 Reducing channel change delay . 23 1.4.2 Reducing energy by avoiding waste . 23 1.4.3 Reducing energy by integrating optical switching . 24 1.4.4 Evaluation . 24 1.5 Outline . 24 2 Background 27 2.1 Video coding . 27 2.1.1 IPTV channel change delay . 28 2.2 IP multicast . 31 2.2.1 Why multicast? . 31 2.2.2 Multicast addresses . 32 2.2.3 Group management . 32 2.2.4 Multicast routing protocols . 33 8 CONTENTS 2.2.4.1 Flood and prune protocols . 33 2.2.4.2 Centre-based trees protocols . 34 2.3 A typical IPTV network . 35 2.3.1 Network topology . 35 2.3.2 Network protocols . 37 2.3.3 IPTV services . 38 2.4 Challenges for IPTV providers . 38 3 State of the art 41 3.1 Measurement of IPTV systems . 41 3.2 A survey on techniques to reduce IPTV channel change delay . 42 3.2.1 Simple optimisations using pure multicast . 43 3.2.2 Proxy server with boost streams . 43 3.2.3 Video coding techniques . 46 3.2.4 Predictive pre-joining of TV channels . 47 3.3 Green networking . 48 3.3.1 Fundamentals . 49 3.3.2 No work? Then, sleep . 50 3.3.3 Little work? Then, slow down: Adaptive Link Rate . 50 3.3.4 Want to sleep? Then, delegate: Proxying . 51 3.3.5 Change paradigm: energy-aware infrastructures . 52 3.3.6 Shifting to save: Traffic Engineering . 53 3.3.7 Lacking information? Measure it . 54 3.4 From electronics to optics . 55 3.4.1 Optics vs electronics: there is room for both . 55 3.4.2 Hybrid architectures: the best of both worlds . 56 4 Methodology and dataset 59 4.1 Methodology . 59 4.2 Dataset . 60 4.2.1 Data collection . 61 4.2.2 Data characterisation . 62 4.2.3 Data cleaning and parsing . 64 4.2.4 Validation of the dataset . 65 5 Reducing channel change delay 69 5.1 Introduction . 70 5.2 Simple scheme: pre-joining neighbouring channels . 73 5.3 Methodology . 73 5.4 Evaluation . 75 5.5 Pre-joining popular TV channels . 78 5.6 Personalised scheme: tracking user behaviour . 80 CONTENTS 9 5.6.1 Evaluation . 82 5.7 Discussion . 83 5.8 Conclusions . 84 6 Resource and energy efficient network 87 6.1 Introduction . 88 6.2 Selective joining . 90 6.3 Methodology . 91 6.4 Evaluation . 94 6.5 Impact on energy consumption . 96 6.5.1 Power consumption model . 96 6.5.2 Results . 98 6.6 Discussion: effect on channel change delay . 102 6.7 Conclusions . 105 7 Optical bypass of popular TV channels 107 7.1 Introduction . 108 7.2 The use of optical bypass to save energy . 110 7.3 Protocol for optical bypass in IPTV . 111 7.4 Methodology . 114 7.5 Evaluation . 115 7.5.1 Scalability.