internet streaming media delivery:
DESCRIPTION
Delving into. Internet Streaming Media Delivery:. A Quality and Resource Utilization Perspective. Lei Guo 1 , Enhua Tan 1 , Songqing Chen 2 , Zhen Xiao 3 , Oliver Spatchcheck 4 , and Xiaodong Zhang 1. Multimedia on the Internet. - PowerPoint PPT PresentationTRANSCRIPT
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Internet Streaming Media Delivery:
Lei Guo1, Enhua Tan1, Songqing Chen2, Zhen Xiao3, Oliver Spatchcheck4, and Xiaodong Zhang1
Delving into
A Quality and Resource Utilization Perspective
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Multimedia on the Internet
• Internet video traffic is doubling every 3 to 4 months (IBLNEWS, comScore)– Youtube nearly doubled its traffic in May– 100 million video streams were served per day in July, 2006
by Alexa Internet
X 400% from May to Oct
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Pseudo Streaming
HTTP
Web server
X 1 hours
Flash based
Short video: 3min
High cost: 1-1.5 million$ a month
RTMP: streaming flash video
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Streaming Media
Akamai, LimeLight Networks
Streaming serverCDN
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Streaming Media
• Merits– Thousands of concurrent streams– Flexible response to network congestion– Efficient bandwidth utilization– High quality to end users
• Challenges– Lack of QoS on the Internet– Diverse network connection of users
• Research and techniques– Effective utilization of server and Internet resources– Protocol rollover, Fast Streaming, MBR and rate adaptation
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Limits of Existing Measurements
• Few studies on the quality and mechanism of streaming media delivery– Coarse granularity studies on access pattern and user behaviors– Small scaled experiments in lab environment– Unknown on the state of the art of Internet streaming delivery– Unknown on the resource utilization of modern streaming services
• Challenge of streaming quality studies– Server logs are not enough– Packet level analysis is difficult: reconstruct TCP flow to get
streaming protocol header
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Our Objective and Methodology
• Understand modern streaming techniques– The delivery quality and resource utilization
• Collect a large streaming media workload – From thousands of home users and business users
Hosted by a large ISP (Gigascope)– RTSP, RTP/RTCP, MMS, RDT packet headers instead of server lo
gs
• Analyze commonly used streaming techniques– Protocol rollover– Fast Streaming– MBR encoding and rate adaptation
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Outline
• Traffic overview
• Protocol rollover
• Fast Streaming
• Rate adaptation
• Conclusion
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Traffic Overview
• User communities– Home users in a cable network– Business users hosted by a big ISP– Have different access patterns
• Media hosting services– Self-hosting– Third-party hosting
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Which is more popular: audio or video?
0.00%
10.00%
20.00%
30.00%
40.00%
50.00%
60.00%
70.00%
Home user Busi ness user
audi ovi deo
Business users access more audio than home users
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On-demand media: File length
Business users tend to access longer audio/video files
Audio Video
pop songs(3-5 min)music
Previews(30 sec)
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On-demand media: Playback duration
Business users tend to play audio/video longer
Audio Video
pop songs
music previews
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Live media: Playback duration
Business users tend to access live audio/video longer
Audio Video
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Media hosting services
Self-hosting: yahoo.com, aol.com, wbr.com
Third-party hosting: akamai.com. LimeLight Networks, fplive.net
CDN/MDN are widely used
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Outline
• Traffic overview
• Protocol rollover
• Fast Streaming
• Rate adaptation
• Conclusion
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Protocol RolloverStreaming server
RTSP/UDP
RTSP/TCP
HTTP/TCP Embed RTSP commands in HTTP packets
Media player
Traffic volume:
UDP: 23%
TCP: 77%
HTTP: rare
X
X
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Protocol rollover time
Windows media service RealNetworks media service
Protocol rollover increases user startup time significantly
Startup latency = protocol rollover time + transport setup time + startup buffering time
Content provider: use URL modifier to specify protocol in the meta file rtspt://xxx.xxx.com:/xxx.wmv (TCP) >70% rtspu://xxx.xxx.com:/xxx.wmv (UDP) rarely
TCP will be used even UDP is supported
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Outline
• Traffic overview
• Protocol rollover
• Fast Streaming
• Rate adaptation
• Conclusion
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Fast Streaming
• Fast Streaming: deliver media data “faster” than its encoding rate– Fast start: fill the initial buffer– Fast cache: optional– Fast recovery– Fast reconnect
• Always TCP-based
Back
40%60%
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Media objects delivered with Fast Cache
File length Encoding rate
Fast Cache is more widely used for media files with longer length and higher encoding rate
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Bandwidth Utilization
PLAY RTSP/1.0Bandwidth: 1.12 MbpsSpeed: 20.5
RTSP /1.0 200 OKSpeed: 5
Fast Cache Normal TCP streaming
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Fast Cache smooth bandwidth fluctuation
Rebuffer ratio = rebuffer time / play time
Fast Cache
Normal TCP
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Fast Cache produces extra traffic
Early termination: most streaming sessions only request the initial part of a media object
Fast Cache: > 55% oversupplied
Normal TCP: < 5% oversupplied
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Server response time
Third party media service Self-hosting media service
DESCRIBE foo.wmv RTSP/1.0
RTSP /1.0 200 OKSDP
RTT
SRT
sniffer
handshake
20 ms
> 40%
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Server Load
Windows media load simulator
Windows Server 2003 Win XP
Server log
…
Ethernet
1 X 4 X
Some CDNs/MDNs do not support Fast Cache at all
Link
Bandwidth CPU
1 X 4 X
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Effectiveness of resource over-utilization
• Fast Cache is TCP-based– Only feasible when bandwidth is large enough– Less possibility of congestion in this case
Encoding rate: 200 – 320 K bpsBandwidth: > 500 Kbps
Fast Cache: not resource-efficient
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Outline
• Traffic overview
• Protocol rollover
• Fast Streaming
• Rate adaptation
• Conclusion
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Rate Adaptation
96Kbps128Kbps320Kbps
… 1.128Mbps
Multiple-bit-rate encoding
Stream switch
Windows: Intelligent streamingRealNetworks: SureStream
Stream thinning: deliver key frame only
Video cancellation: play audio only
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MBR encoding
on-demand audio
live audio
audio stream in video objects
video stream in video objects
42% on-demand video are MBR encodedMaximum streams in a video: 20
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Stream switch
30 sec
60%
Streaming switch latency Low quality duration
3 sec
40%
Play-out buffer
Stream switch is often not smooth
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Fast Cache and stream switch
Do not work with each other: stream switch is disabled in Fast Cache
playing buffering playing buffering bufferingplaying
5 sec
When network congestion occurs …
Like pseudo streaming
When rebuffer occurs
time
fill play-out buffer
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Streaming quality and playback duration
Home user business user
Longer duration sessions have higher prob. of quality degradation
Business user workload has more quality degradation due to the longer playback time
>100 sec
88%
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Coordinating caching and rate adaptation
• Fast Cache: aggressively buffer data in advance– Over-utilize CPU and bandwidth resources– Neither performance effective nor cost-efficient
• Rate adaptation: conservatively switch to lower bit rate stream– Switch handoff latency
• Coordinated Streaming
Upper boundPrevent aggressive buffering
Lower boundPrevent switch latency
high rate stream
low rate stream
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Conclusion
• Quality of Internet streaming– Often unsatisfactory– Need to improve
• Modern streaming media services– Over-utilize CPU and bandwidth resources– Not a desirable way to improve quality
• Coordinated Streaming– Combine merits of both caching and rate adaptation– Simple but effective
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Thank you!Thank you!
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Traffic Overview
• Different access patterns in user communities– Not due to the business related media traffic: both are
news and entertainment sites– Working environment affects access pattern
• Media hosting services– Self-hosting– Third-party hosting
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Streaming quality summary
The quality of media streaming on the Internet leaves much to be improved
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Stream thinning (play key frames only)
30 sec
70%
+Stream thinning duration
Thinning intervalSmooth play
Key frame play