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Technical University of Turin, Computer Engineering Department,
Date & time: Tuesday, June 14, 2005, 9:00-13:00
Location: Faculty of Electrical Engineering and
Computing, room: White Hall
Applications that require real-time interaction
among their users are gaining importance and diffusion as computer
networks become increasingly powerful and ubiquitous. Many such
applications impose very stringent requirements on the network;
among the applications today widely deployed, videoconferencing
is most demanding.
In order for the participants in a videoconference call to interact
naturally, the end-to-end delay should be below human perception;
even though an objective and unique figure cannot be set, 100
ms is widely recognized as the desired one way delay requirement
Since the global propagation delay alone can be about 100 ms,
the actual end-to-end delay budget available to the system designer
(excluding propagation delay) is very limited (e.g., no more than
We identify the components of the end-to-end delay in various
configurations with the objective of understanding how it can
be kept below the desired 10 ms bound.
After an overview of the distinctive features of interactive
multimedia applications, their requirements on the network are
discussed and limited delay and delay variation (Jitter) identified
as the most demanding requirements. The most common tools for
controlling service quality are presented and the two major frameworks
for their deployment within IP networks, i.e., Integrated Services
(IntServ) and Differentiated Services (DiffServ), outlined. The
tutorial also studies the implications of the architecture of
packet switches on delay bounds.
Then the tutorial delves into more detail by analyzing the end-to-end
delay components of a videoconferencing system step-by-step, through
six system configurations obtained by combining three generic
network architectures with two video encoding schemes: the transmission
of raw video and variable bit rate (VBR) MPEG video encoding over
(i) circuit switching
(ii) synchronous packet switching, and
(iii) asynchronous packet switching.
Various queuing and scheduling algorithms for asynchronous and
synchronous packet networks will be analyzed and compared.
The tutorial finally shows that having a global common time reference,
together with an innovative queuing and scheduling scheme called
time-driven priority (TDP) and VBR MPEG video encoding, provides
adequate end-to-end delay, which is
(i) below 10 ms,
(ii) independent of the network instant load, and
(iii) independent of the connection rate.
The participants are expected to have basic knowledge on packet
switching and the Internet Protocol Suite. Depending on the background
of the audience, the first part of the tutorial can be organized
as a quick overview of the general context to which the remainder,
or as an in-depth discussion.
- Multimedia networking: distinctive features and requirements
of interactive multimedia applications
- Analysis of delay components in multimedia communications
- Controlling the network delay
- statistical multiplexing and delay
- queuing and scheduling algoriths
- Fixed Priority
- Round Robin
- Class based queuing
- Weighted fair queuing
- Time driven priority
- switch architectures for controlled delay
- Quality of service in the Internet
- Integrated Services
- Differentiated Services
- Encoding and transmission of MPEG video: a closer look
- video over circuit
- video over asynchronous packet switching
- VBR video with time-driven priority
Dr. Mario Baldi is Associate Professor on tenure track at the
Computer Science Department of Technical University of Turin,
Italy, and Vice President for Protocol Architecture at Synchrodyne
Networks, Inc., New York.
He received his M.S. Degree Summa Cum Laude in Electrical Engineering
in 1993, and his Ph.D. in Computer and System Engineering in 1998
both from Torino Polytechnic.
Mario Baldi has been Honorary Visiting Professor at La Trobe
University, Melbourne, Victoria, Australia, Adjunct Professor
at Univerity of Illinois at Chicago, and visiting researcher at
the IBM T. J. Watson Research Center, Yorktown Heights, NY, at
Columbia University, New York, NY, and at the International Computer
Science Institute (ICSI), Berkeley, CA.Mario Baldi has been visiting
researcher at the IBM T. J. Watson Research Center, Yorktown Heights,
NY, at Columbia University, New York, NY, and at the International
Computer Science Institute (ICSI), Berkeley, CA.
As part of his extensive research activity at Torino Polytechnic,
Mario Baldi has been leading various networking research projects,
involving Universities and industrial partners, funded by European
Union, Local Government, and various companies, including Telecommunications
Carriers, such as Infostrada and Telecom Italia, and research
institutions, such as Telecom Italia Labs.
Mario Baldi co-authored over 50 papers on various networking
related topics and two books, one on internetworking and one on
switched local area networks.
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