1. Internet Streaming Media Delivery:
Delving into
Internet Streaming Media Delivery:
A Quality and Resource Utilization Perspective
Lei Guo1, Enhua Tan1, Songqing Chen2, Zhen Xiao3,
Oliver Spatchcheck4, and Xiaodong Zhang1

2. 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

3. Pseudo Streaming HTTP Flash based Short video: 3min
Web server
Flash based
Short video: 3min
High cost: million$ a month
RTMP: streaming flash video
HTTP
X 1 hours

4. Streaming Media
CDN
Streaming server
Akamai,
LimeLight Networks

5. Streaming Media Merits Challenges Research and techniques
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
In 2000, 9,000 narrowband and 2,400 broadband video streams on a single physical server

6. 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

7. 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 logs
Analyze commonly used streaming techniques
Protocol rollover
Fast Streaming
MBR encoding and rate adaptation

8. Outline Traffic overview Protocol rollover Fast Streaming
Rate adaptation
Conclusion

9. Traffic Overview User communities Media hosting services
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

10. Which is more popular: audio or video?
Business users access more audio than home users

11. On-demand media: File length
Audio
Video
pop songs
(3-5 min)
music
Previews
(30 sec)
Business users tend to access longer audio/video files

12. On-demand media: Playback duration
Audio
Video
pop
songs
music
previews
Business users tend to play audio/video longer

13. Live media: Playback duration
Audio
Video
Business users tend to access live audio/video longer

14. 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

15. Outline Traffic overview Protocol rollover Fast Streaming
Rate adaptation
Conclusion

16. Protocol Rollover X X Streaming server Media player RTSP/UDP RTSP/TCP
Embed RTSP commands in
HTTP packets
HTTP/TCP
Traffic volume:
UDP: 23%
TCP: 77%
HTTP: rare

17. Protocol rollover time
Startup latency = protocol rollover time + transport setup time + startup buffering time
Windows media service
RealNetworks media service
TCP will be used even UDP is supported
Protocol rollover increases user startup time significantly
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

18. Outline Traffic overview Protocol rollover Fast Streaming
Rate adaptation
Conclusion

19. 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
60%
40%
Back

20. 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

21. Bandwidth Utilization
PLAY RTSP/1.0
Bandwidth: 1.12 Mbps
Speed: 20.5
RTSP / OK
Speed: 5
Fast Cache
Normal TCP streaming

22. Fast Cache smooth bandwidth fluctuation
Rebuffer ratio = rebuffer time / play time
Fast Cache
Normal TCP

23. Fast Cache produces extra traffic
Early termination: most streaming sessions only request the initial part of a media object
Normal TCP: < 5% oversupplied
Fast Cache: > 55% oversupplied

24. Server response time DESCRIBE foo.wmv RTSP/1.0 SRT handshake RTT
sniffer
RTSP / OK
SDP
Third party media service
Self-hosting media service
> 40%
20 ms

25. Some CDNs/MDNs do not support Fast Cache at all
Server Load
Windows Server 2003
Win XP
Windows media
load simulator
Ethernet …
Server log
1 X X
1 X X
Some CDNs/MDNs do not support Fast Cache at all
Link
Bandwidth
CPU

26. 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 bps
Bandwidth: > 500 Kbps
Fast Cache: not resource-efficient

27. Outline Traffic overview Protocol rollover Fast Streaming
Rate adaptation
Conclusion

28. Rate Adaptation Windows: Intelligent streaming
Multiple-bit-rate encoding
96Kbps
128Kbps
320Kbps …
1.128Mbps
Stream switch
Windows: Intelligent streaming
RealNetworks: SureStream
Stream thinning: deliver key frame only
Video cancellation: play audio only

29. 42% on-demand video are MBR encoded Maximum streams in a video: 20
MBR encoding
on-demand audio
audio stream in video objects
live audio
video stream in video objects
42% on-demand video are MBR encoded
Maximum streams in a video: 20

30. Stream switch is often not smooth
Play-out buffer
Streaming switch latency
Low quality duration
40%
30 sec
60%
3 sec
Stream switch is often not smooth

31. Fast Cache and stream switch
Do not work with each other: stream switch is disabled in Fast Cache
When network congestion occurs …
fill play-out buffer
playing
buffering
playing
buffering
playing
buffering
time
5 sec
Like pseudo streaming
When rebuffer occurs

32. Streaming quality and playback duration
Home user
business user
>100 sec
88%
Longer duration sessions have higher prob. of quality degradation
Business user workload has more quality degradation
due to the longer playback time

33. 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
high rate stream
low rate stream
Lower bound
Prevent switch latency
Upper bound
Prevent aggressive buffering

34. 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

35. Thank you!

36. 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

37. Streaming quality summary
The quality of media streaming on the Internet leaves much to be improved

38. Stream thinning (play key frames only)
Thinning interval
Smooth play
Key frame play +
Stream thinning duration
30 sec
70%