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Peer-to-Peer Television for the IP Multimedia Subsystem

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  1. Peer-to-Peer Televisionfor theIP Multimedia Subsystem Alex Bikfalvi Jaime García-Reinoso

  2. Outline Background Motivation • Contributions • Peer-to-peer streaming • IP Multimedia Subsystem I • Peer-to-Peer Television for the IMS • Service architecture • Signaling protocol • Support for mobility II The User Activity in IPTV Data and modeling • Synthesis III Enhancements at the Application Server Signaling delay • Multiple TV channels IV • Performance Evaluation • Basic evaluation • Hybrid streaming V • Conclusions • Summary • Publications • Future enhancements VI Peer-to-Peer Television for the IP Multimedia Subsystem

  3. Part I Background Peer-to-Peer Television for the IP Multimedia Subsystem

  4. Motivation • Internet Protocol Television • Increasing interest in the recent years • Deployments and triple-play packages • Competition with Internet Services 1 • Next Generation Network • Flexible platform for any type of service • Decouples service provisioning from the network • Adequate level of quality of service (QoS) 2 • IP Multimedia Subsystem • Framework for IP multimedia services • Session control using the Session Initiation Protocol (SIP) 3 • TISPAN • Extended IMS NGN to multiple access technologies • Services standardization, including IPTV 4 Peer-to-Peer Television for the IP Multimedia Subsystem

  5. Motivation • In TISPAN, broadcast television uses IP multicast • Large number of TV channels • Static multicast: inefficient for many TV channels • Dynamic multicast: delay and scalability issues • Administrative and economic reasons • Support for multiple transport protocols High performance Availability with existing protocols and equipments Commercial IPTV deployments: walled gardens Peer-to-Peer Television for the IP Multimedia Subsystem

  6. Going Peer-to-Peer… • Peer-to-peer television (P2PTV) service for the IP Multimedia Subsystem • Exploit the unused download and upload capacity Peer-to-Peer Television for the IP Multimedia Subsystem

  7. Going Peer-to-Peer… • Peer-to-peer television (P2PTV) service for the IP Multimedia Subsystem • Exploit the unused download and upload capacity • Dedicated user equipments (set-top boxes) • Streaming transparent to the user Peer-to-Peer Television for the IP Multimedia Subsystem

  8. … with the IMS • Peer-to-peer television (P2PTV) service for the IP Multimedia Subsystem • Application Server • Control service access • Manage peer participation • Implement enhancements • User Equipment (peer) • Download current channel • Download other streams • Upload streams to other peers Peer-to-Peer Television for the IP Multimedia Subsystem

  9. Challenges • We don’t break new ground in peer-to-peer streaming • However… • Integration with a commercial-grade service • Multiple TV channels increase peer churn (over 60% of channel changes in 10 seconds[1,2]) • IMS signaling requirements increase the setup delay • Two enhancements… • Fast signaling • Inactive uploading sessions with committed QoS resources • Low churn • Peer participation on multiple TV channels[3] 1 2 [1] Cha et al., Watching Television Over an IP Network, 2008 [2] Qiu et al., Modeling user activities in a large IPTV system, 2009 [3] Wu et al,. View-upload decoupling: A redesign of multichannel P2P video systems, 2009 Peer-to-Peer Television for the IP Multimedia Subsystem

  10. Part I Background Peer-to-Peer Streaming Peer-to-Peer Television for the IP Multimedia Subsystem

  11. Peer-to-Peer Streaming • Emerged as a response to IP multicast issues • Support • Scalability • Cost • Resources • Complex • IP multicast Low Low Low Med Low • CDN High Med High Med Med • P2P Low High High High High • Initially P2P emulated IP multicast • Application-level multicast • Data forwarded along a tree overlay between hosts Peer-to-Peer Television for the IP Multimedia Subsystem

  12. Peer-to-Peer Streaming • Overlay tree between end-hosts or peers • Data flow may be push or pull • Accommodates one stream or channel Peer-to-Peer Television for the IP Multimedia Subsystem

  13. Peer-to-Peer Streaming • Overlay tree between end-hosts or peers • Data flow may be push or pull • Accommodates one stream or channel • Churn: interruptions due to the departing peers Peer-to-Peer Television for the IP Multimedia Subsystem

  14. Multiple TV Channels • Increased peer churn due to channel changes • View-upload decoupling[1] [1] Wu et al., View-upload decoupling: A redesign of multichannel P2P video systems, 2008 Peer-to-Peer Television for the IP Multimedia Subsystem

  15. Part I Background The IP Multimedia Subsystem Peer-to-Peer Television for the IP Multimedia Subsystem

  16. The IP Multimedia Subsystem • Next Generation Networks • Integrated broadband IP networks for multimedia services Third Generation Partnership Project (3GPP) IP Multimedia Subsystem • Quality of service • Service implementation • Seamless mobility • Authentication, policy and charging Decouples service from the transport network Functional entities and standardized interfaces Peer-to-Peer Television for the IP Multimedia Subsystem

  17. The IP Multimedia Subsystem Gateways Application plane Control plane Policy and charging Transport plane Proxy Serving Applications servers Subscriber database Call-session control Peer-to-Peer Television for the IP Multimedia Subsystem

  18. Part II Peer-to-Peer Television for the IP Multimedia Subsystem Peer-to-Peer Television for the IP Multimedia Subsystem

  19. Service Architecture • Common platform for IPTV streaming using peer-to-peer technology: P2PTV Broadcast Servers P2PTV Application Server User Equipment Peer-to-Peer Television for the IP Multimedia Subsystem

  20. Application Server • SIP Signaling • Manage the IMS multimedia sessions with the UE • User agent server • Sessions terminating at the P2PTV-AS • Streaming by the broadcast server • sip:p2ptv-as.example.net P2PTV-AS UAS 2 • sip:alice@example.net S-CSCF UE 1 • INVITE sip:p2ptv@example.net • From: sip:alice@example.net • To: sip:p2ptv@example.net • Call-ID: 1000 Peer-to-Peer Television for the IP Multimedia Subsystem

  21. Application Server • SIP Signaling • Manage the IMS multimedia sessions with the UE • Back-to-back user agent • Peer-to-peer streaming • sip:p2ptv-as.example.net P2PTV-AS B2BUA • sip:alice@example.net • sip:bob@example.net S-CSCF UE UE • From: sip:p2ptv@example.net • To: sip:bob@example.net • Call-ID: 4000 • From: sip:alice@example.net • To: sip:p2ptv@example.net • Call-ID: 3000 Peer-to-Peer Television for the IP Multimedia Subsystem

  22. Channel Streaming • The P2P push-pull streaming generates an overlay A TV channel is divided in multiple (e.g. 3) streams Ideally, a UE peer downloads all streams when tuning to the channel A UE peer may upload one or more streams to overlay neighbors This strategy works well with multiple description codecs such as H.264/SVC Peer-to-Peer Television for the IP Multimedia Subsystem

  23. Streaming Enhancements • We face the following challenges… • The IMS session signaling is an expensive operation • Streaming multiple channels with a classic experience • We propose two solutions… • Fast signaling • Inactive uploading sessions with committed QoS resources • Low churn • Peer participation on multiple TV channels 1 2 • The first targets the control plane • The second targets the media plane Peer-to-Peer Television for the IP Multimedia Subsystem

  24. Fast Signaling • The P2P streaming requires two multimedia sessions • Downloading side, low dynamics, reusable during channel changes • Uploading side, high dynamics, non-reusable during channel changes The performance bottleneck is on the upload side Introduce foster peers with inactive upload sessions These accommodate new requests without establishing new sessions Peer-to-Peer Television for the IP Multimedia Subsystem

  25. Fast Signaling • Situations that benefit from foster peers • Fast stream change when the user changes the current channel • Fast recovery to accommodate peer churn when occurs Number of inactive sessions Changing stream 1 2 1 Fast stream change Fast recovery Peer-to-Peer Television for the IP Multimedia Subsystem

  26. Fast Signaling • Does not require a new session on the upload side • Initiated by the P2PTV-AS as a response to user demand sip:alice@example.net sip:bob@example.net P2PTV-AS PCRF UE S-CSCF P-CSCF INVITE 1 INVITE INVITE INVITE sip:alice@example.net ... From: sip:p2ptv@example.net ... i=stream 100 a=inactive 183 Session Progress 183 Session Progress AA-Request 183 Session Progress 2 AA-Answer Peer-to-Peer Television for the IP Multimedia Subsystem

  27. Fast Signaling • Changing the TV stream using a foster peer sip:alice@example.net sip:bob@example.net UEup UEdown P-CSCF S-CSCF P2PTV-AS UPDATE 1 UPDATE UPDATE UPDATE UPDATE sip:p2ptv@example.net ... From: sip:alice@example.net To: sip:p2ptv@example.net ... i=stream 100 c=IN IP4 10.0.0.1 a=curr:qoslocal recv a=curr:qosremotesend UPDATE sip:bob@example.net ... From: sip:p2ptv@example.net To: sip:bob@example.net ... i=stream 100 c=IN IP4 10.0.0.1 a=curr:qoslocal send a=curr:qosremoterecv 200 OK 200 OK 200 OK 200 OK Peer-to-Peer Television for the IP Multimedia Subsystem

  28. Fast Signaling • It sounds simple, but… • How many inactive sessions accommodate the TV channel demand? • Too few, no fast signaling and high channel change delay • Too many, waste network resources with reserved bandwidth 1 User activity wi 2 Inactive sessions On a given TV channel Peer-to-Peer Television for the IP Multimedia Subsystem

  29. Peer Churn • Peers download streams from multiple TV channels • Primary streams correspond to the current TV channel • Secondary streams from other TV channels Only the primary streams are affected by the channel change churn Primary streams are used for viewing Secondary streams are used for uploading The cost is the increased bandwidth usage Peer-to-Peer Television for the IP Multimedia Subsystem

  30. Peer Churn • This is view-upload decoupling: can we do better? • Complete decoupling wastes bandwidth • Upload primary streams for peers with free bandwidth Peers may need a new download session at the next channel change Primary streams become secondary Self-organizing, no centralized assignment of secondary streams Higher delay: use inactive download sessions Peer-to-Peer Television for the IP Multimedia Subsystem

  31. Peer Coordination • The session coordination computes the number of inactive sessions for a channel wi • The peer coordination assigns peer resources… • … to accommodate the demand We discuss both algorithms in further detail in part IV Peer-to-Peer Television for the IP Multimedia Subsystem

  32. Part II Peer-to-Peer Television for the IP Multimedia Subsystem Support for Mobility Peer-to-Peer Television for the IP Multimedia Subsystem

  33. Support for Mobility • We examine the performance in roaming situations • Minimize the loss of streaming data… • Buffering mechanism compensating for connectivity loss • Reducing the handover delay • Existing solutions… • SIP • Establish a new session after roaming to the new network • Optimized SIP • Transfer the session context between the old and new P-CSCF to meet the session preconditions • Mobile IP • Tunnel the video data from the home to the visited network 1 2 3 Peer-to-Peer Television for the IP Multimedia Subsystem

  34. Proactive Context Transfer • Unfortunately… • The UE must reestablish the session in the new network • We exploit the handover delay when the UE is disconnected • The network takes an active participation in the handover • Use the IEEE 802.21 (MIH) standard • One in every network • Part of the MIH point-of-service • Notified by the UE before the handover • Installs the session context in the network at the P-CSCF • Applies to SIP or MIP mobility • Proactive Context Transfer Service Application Server Peer-to-Peer Television for the IP Multimedia Subsystem

  35. Performance Evaluation • Comparing the handover delay with previous scenarios Home Visited SIP MIP • Delay components Total handover delay for UMTS SIP and MIP handover delay Peer-to-Peer Television for the IP Multimedia Subsystem

  36. Part III The User Activity Peer-to-Peer Television for the IP Multimedia Subsystem

  37. Objectives • Essential for system design and performance evaluation • Measurement studies… • Internet-based services like PPLive, PPStream, SopCast[1,2,3,4,5] • Telco IPTV such as TelefonicaImagenio, AT&T U-Verse[6,7,8] • Simulwatch • Synthetic workload generator by Qiu et al. • Limited number of properties • Low accuracy for some metrics • Some flaws [1] Ali et al., Measurement of commercial peer-to-peer live video streaming, 2006 [2]Hei et al., A measurement study of a large-scale P2P IPTV system, 2007 [3]Silverston et al., Measuring P2P IPTV systems, 2007 [4]Xie et al., A measurement of a large-scale peer-to-peer live video streaming system, 2007 [5] Vu et al., Measurement of a large-scale overlay for multimedia streaming, 2007 [6] Cha et al., Watching television over an IP network, 2008 [7] Qiu et al., Modeling user activities in a large IPTV system, 2009 [8] Qiu et al., Modeling channel popularity dynamics in a large IPTV system, 2009 Peer-to-Peer Television for the IP Multimedia Subsystem

  38. User Activity • The state of the user equipment and current channel[1] Offline session Online session Channel session [1] Qiu et al., Modeling user activities in a large IPTV system, 2009 Peer-to-Peer Television for the IP Multimedia Subsystem

  39. User Activity • The state of the user equipment and current channel[1] Online events Offline events • Session length • Session rate Peer-to-Peer Television for the IP Multimedia Subsystem

  40. Session Length • A hyper-exponential distribution Online session interval length • Fitting algorithm of Feldmann et al.[1] • Fit each exponential on exponentially spaced intervals [1]Feldmann et al., Fitting mixtures of exponentials to long-tail distributions to analyze network performance models, 1998 Peer-to-Peer Television for the IP Multimedia Subsystem

  41. Session Rate • Has a complex daily and weekly pattern 60 min 20 min 10min 6.66min 30 min 15min Difficult to model Online session rate (normalized) Frequency spectrum • Qiu et al. model the spectrum with a continuous distribution • Limited accuracy: does not include phase information • Propose dominant frequency components based on power Peer-to-Peer Television for the IP Multimedia Subsystem

  42. Session Rate • Has a complex daily and weekly pattern 60 min 20 min 10min 6.66min 30 min 15min Difficult to model 59+57 parameters 9+7 parameters Online session rate (normalized) Frequency spectrum • Qiu et al. model the spectrum with a continuous distribution • Limited accuracy: does not include phase information • Propose dominant frequency components based on power Peer-to-Peer Television for the IP Multimedia Subsystem

  43. Session Rate • Include weekly pattern using a modulating function • Stochastic properties • Difference between trace and model: normal distribution • Based on the number of online viewers Peer-to-Peer Television for the IP Multimedia Subsystem

  44. Workload Synthesis • Generate workload based on analytical model • Incomplete measurement data on IPTV user activity[1,2,3] • Rescale workload dimensions like users or channels • Conclusions • Better approximation of the activity data • Exclude some details like user preference Online event Offline event Online interval Timeline Offline interval Channel event Channel interval [1] Cha et al., Watching television over an IP network, 2008 [2] Qiu et al., Modeling user activities in a large IPTV system, 2009 [3] Qiu et al., Modeling channel popularity dynamics in a large IPTV system, 2009 Peer-to-Peer Television for the IP Multimedia Subsystem

  45. Part IV The Application Server Peer-to-Peer Television for the IP Multimedia Subsystem

  46. Application Server Functions • SIP Signaling • Manage the IMS multimedia sessions with the UE 1 • Session Coordination • Compute the number of inactive upload sessions 2 • Peer Coordination • Assignment of peer bandwidth across TV streams 3 Peer-to-Peer Television for the IP Multimedia Subsystem

  47. Session Coordination • The system is like a queue for every TV channel Disturbance User activity u(t), zch(t) On a given TV channel Active sessions wa Arrival zch Input Blocking ratio β and utilization ρ Output Number of sessions w(t)=wa(t)+wi(t) Inactive sessions wi Blocking From the perspective of the fast signaling Service dch Peer-to-Peer Television for the IP Multimedia Subsystem

  48. Session Coordination • Finding a relationship between input and output • No simple distribution for the user activity dynamics • The temporal dimension is an important element Arrivals served Arrivals blocked If the arrival would be a Poisson process and the service rate have an exponential distribution The number of upload session computed using the Erlang-B equation No strong correlation between the channel user activity and the optimal number of upload sessions Simulation of the user arrival Peer-to-Peer Television for the IP Multimedia Subsystem

  49. Session Coordination • Use an adaptive algorithm with a feedback loop Time-discrete system: t  k SCA Input: r Output: w(k) User activity: u(k) Reference: r Error: e(k) Input: w(k) Output: y(k) Controller System Delay • Design tasks… • Selection of the control signals: input, output and reference • Determine the controller transfer function: Peer-to-Peer Television for the IP Multimedia Subsystem

  50. Session Coordination • Performance evaluation • A large P2PTV deployment with 100 000 subscribers • Synthetic workload spanning 1 week Blocking ratio around the desired reference value The session utilization is between 90% and 100% Session utilization ρ(k) Blocking ratio b(k) Peer-to-Peer Television for the IP Multimedia Subsystem