Transcript Distributed Multimedia Systems

Distributed Multimedia
Systems
James Maxlow
March 24th, 2003
Introduction
 Most multimedia is inherently time-based –
the arrival time and arrival order of data
packets is important
 The Internet guarantees neither when
transmitting data
 We don’t just want interactive multimedia
over our networks… we want it to be
reliable and high-quality
 A distributed multimedia system can come
to the rescue
History
 60s-70s: Distributed computing research
with earliest networks
 80s: Compact disc, personal computer
explosion
 80s-90s: Distributed multimedia system
research (video conferencing, et al)
 90s: Current prevalent paradigm (quality of
service management)
Goal
 Simplicity in and of itself: We want and
need high quality, reliable, interactive
multimedia
 The general Internet structure is not
sufficient to accomplish this
 A distributed multimedia system will add
protocols and architectures on top of the
Internet (or LAN) to guarantee quality
levels, thereby satisfying our need
Definitions
 Bandwidth: data rate through a component
 Latency: time needed for a packet to travel
end to end
 Loss rate: acceptable drop-frame ratio
 Quality of service management:
negotiation and allocation of computing
resources
Definitions
 Flow specification: explicit representation
of required resources
 Traffic shaping: using buffers at source
and destination to smooth data flow
 Admission control: allowing or denying
client requests based on available
resources
Features and Structure
1: Sources provide flow spec to main QOS manager through
local QOS managers
2: Main QOS ready to reserve resources
3: Client send request to main QOS
Source
QOS
Source
QOS
Source
QOS
4: Main QOS decides if client can be served based on available
resources
5: If so, main QOS tells local QOS to allocate resources (if not,
client is rejected)
6: Service begins
7: Main QOS and local QOS monitor resource usage / quality,
adjust allocated resources if necessary
8: Return to step 4 if new client connects
Main QOS
9: Service ends, resources are freed
Controller
Client
Transmission Line (Internet)
How To Use
 A distributed multimedia system is a
combination of source hardware, QOS
manager software, and a transmission line
 Can be bought as a complete, dedicated,
proprietary package – very expensive!
 Can be built using existing hardware and
Internet / LAN connection lines… all that is
needed beyond that is QOS management
software – can be purchased or developed
Applications
 Video conferencing
 Live news feeds
 Video-on-demand
 Remote-control of exploratory robots
 Remote musical collaborations
 Remote surgical operations
Significant Points
 Distributed multimedia systems exist to
guarantee quality of delivery levels
 Resource reservation is the key
 Additional clients do not degrade system –
they can be refused if resources are
scarce
 Quality guarantees are of paramount
importance, whether used for business,
entertainment, scientific or health-related
applications
Summary
 Serving multimedia requires strict resource control to
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maintain quality
Resources consist of bandwidth, latency, and loss
rate, among others
Source components declare the resources they need
in flow specifications
Quality of service managers negotiate and reserve
resources to guarantee quality
Source + flow spec + QOS manage + transmission
lines = distributed multimedia system
References
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Bashandy, Ahmed, Paul, R., Baqai, S., Sedigh, S., Fahmi, H., Ghafoor, A. “A Protocol Architecture for
Guaranteed Quality of Service in Collaborated Multimedia Applications.” Proceedings of the IEEE
Symposium on Application -Specific Systems and Software Engineering & Technology. 1999.
Coulouris, George, Dollimore, J., Kindberg, T. Distributed Systems Concepts and Design, Third Edition. New
York: Addison Wesley, 2001.
Karr, David, Rodrigues, C., Loyall, J., Schantz, R., Krishnamurthy, Y., Pyarali, I., Schmidt, D. “Application of
the QuO Quality-of-Service Framework to a Distributed Video Application.” Proceedings of the
International Symposium on Distributed Objects and Applications. 2001.
Loyall, Joseph, Schantz, R., Zinky, J., and Bakken, D. “Specifying and Measuring Quality of Service in
Distributed Object Systems.” Proceedings of the 1st International Symposium on Object-Oriented
Real-Time Distributed Computing. 1998.
Stobart, Joel. “The use of Videoconferencing as a function of distributed organization: The differences of
implementation depending on scale.” Papers of the 2nd Annual Conference on Multimedia Systems,
Southampton Univ., UK. 2002.
Xu, Dongyan, Nahrstedt, K., Wichadukal, D. “QoS and Contention-Aware Multi-Resource Reservation.”
Cluster Computing 4, pp. 95-107. 2001.
Websites:
http://www.cse.msu.edu/icdcs/ “ICDCS 2003”
http://www.idms2001.org/ “iDMS 2001”
http://mips2003.idms-proms.org/ “MIPS 2003”
http://iwqos03.cs.berkeley.edu/ “IWQoS 2003”
http://www.computer.org/computer/timeline/ “Timeline of Computing History”