Towards Peer-Assisted Dynamic Adaptive Streaming over HTTP
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Transcript of Towards Peer-Assisted Dynamic Adaptive Streaming over HTTP
Towards Peer-Assisted Dynamic Adaptive Streaming over HTTP
Stefan Lederer, Christopher Müller and Christian Timmerer
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PV 2012 | Peer-Assisted DASH Slide 2
Introduction
• Video streaming needs huge bandwidth ressources
• Can other peers be used to reduce the server load and save costs?
• Can this be integrated into DASH?
PV 2012 | Peer-Assisted DASH Slide 3
Towards Peer-Assisted DASH• Reduction of server load
• Clients offer their downloaded segments– Segment requests are monitored by server– Integration in DASH MPD for future clients
• Intelligent Scheduling Algorithms necessary– When to load from peer, when from server? – Error Handling, etc.
PV 2012 | Peer-Assisted DASH Slide 4
Peer Assisted Streaming
• Peer Traffic– Non-symmetric Internet Connection– Bottleneck: Low Upload Resources
• Split segments to smaller sub-chunks • Restrict number of accepted connection at client• Limit connection duration to prevent stalls
• Target: – Reduce server bandwidth by 10 - 20 %
PV 2012 | Peer-Assisted DASH Slide 5
Peer Assisted Streaming
PV 2012 | Peer-Assisted DASH Slide 6
Implementation
• Proof of Concept using DASH VLC Plugin + PHP for server-side implementation– Provides basic proof of concept and shows
weaknesses to improve– Problem: Amount of clients too low
• Detailed Evaluation in Omnet++– Larger scale simulation with 40 clients– Deterministic client behaviour scenarios
PV 2012 | Peer-Assisted DASH Slide 7
MPD Tracking Server (1)
• MPD Import– Imports original MPD to database
• MPD Generator– Generates MPD based on database– Including other peers using <BaseURL>
– Client has the possibility to update its MPD– Use @MediaRange to signal segment size – Use ZIP compression to reduce MPD size
PV 2012 | Peer-Assisted DASH Slide 8
MPD Tracking Server (2) andClient Modifications• File Tracker
– Gateway for segment access– Segment + Representation as parameter– Stores client IP + timestamp for upcoming MPD
requests– Response: the requested segment
• Local HTTP Server + Buffer at Client– Store segments to disc and provide them on
demand via a local HTTP server
PV 2012 | Peer-Assisted DASH Slide 9
<MPD> <BaseURL> http://www.cdn.com/tracker.php?file= </BaseURL> <Period> <AdaptationSet bitstreamSwitching="true"> <Representation bandwidth="2000000"....>
<BaseURL>http://client1-IP/example</BaseURL>
<BaseURL>http://client2-IP/example</BaseURL> <SegmentList duration="4"> <SegmentURL
media=“rep2MBit_segment1.mp4"> </SegmentList> </Representation> <Representation bandwidth="4000000"....
<BaseURL>http://client1-IP/example</BaseURL> <!-- further base urls and Segments --> </Representation> <!-- further representations --> </AdaptationSet> </Period>...
MPD Example
Server URL withFile Tracker
Peers offering the segment
PV 2012 | Peer-Assisted DASH Slide 10
Peer Assisted DASHExample
PV 2012 | Peer-Assisted DASH Slide 11
Evaluation
• OMNet++– Simulation framework– INET framework for protocol stack– HTTP Client/Server implementation– DASH Client based on DASH VLC Plugin / libDASH– MPD Generator + Segment Tracker using external
MySQL database
PV 2012 | Peer-Assisted DASH Slide 12
Evaluation Settings
Bitrate Resolution
101 kbit/s. 320x240
201 kbit/s. 480x360
395 kbit/s. 480x360
800 kbit/s. 854x480
1372 kbit/s. 853x480
1992 kbit/s. 1280x720
2995 kbit/s. 1920x1080
3992 kbit/s. 1920x1080
4979 kbit/s. 1920x1080
5936 kbit/s. 1920x1080
PV 2012 | Peer-Assisted DASH Slide 13
Simulation 1:Results – Server
- 15 %
• 6 Mbps maximumRepresentation limit
• Clients select different representations according to their downlink speed- Number of clients offering
one specific segment is low
PV 2012 | Peer-Assisted DASH Slide 14
Simulation 2:Results - Server
- 25 %
• 1,4 Mbps maximumRepresentation limit
• Clients select the same maximum representation- Downlink speed of all
clients is sufficient - Lower upload time for
segments
PV 2012 | Peer-Assisted DASH Slide 15
Simulation ResultsExample Client
• Client:– 8 Mbps Downlink– Activation at
second 214 of the simulation
• Simulation 2:– 1,4 Mbps max.
Representation limit
PV 2012 | Peer-Assisted DASH Slide 16
Cost Saving Possibilities
• Simulation 1: 15 % traffic cost reduction– Total costs: US$ 4.14 per hour – Savings: US$ 0.62 per hour
• Additionally: Reduced reserved bandwidth capacity
PV 2012 | Peer-Assisted DASH Slide 17
Conclusions
• Torwards Peer-Assisted DASH– Peer-assited streaming using standard-compliant
DASH MPDs– Maintainance of DASH advantages – Relative simple system design and implementation
work
• Evaluation simulation– Up to 25 % bandwidth savings– Directly convertable to CDN cost reductions
PV 2012 | Peer-Assisted DASH Slide 18
Conclusions & Further Work
• Much more possibilities– Intelligent client clustering in larger scale
environments– Peer management & download algorithm
improvements– MPD update improvements– Detailed CDN cost analysis – Evaluation of some Set-Top box scenarios– Integration to Content Centric Networking (CCN)
The END
http://dash.itec.aau.at
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