Presentation Planning for Distributed Video Systems
Presentation Planning for Distributed Video Systems
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Date
1998-10-15
Authors
Hwang, Eenjun
Prabhakaran, B.
Subrahmanian, V.S.
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Abstract
A distributed video-on-demand system is one where a collection of
video data is located at dispersed sites across a computer network.
In a single-site environment, a local video server retrieves video data
from its local storage device (or devices). However, in the setting of a
distributed VoD system, when a customer requests a movie from his/her
local server, the server may need to interact with other servers located
across the network. In this paper, we present three types of presentation
plans, that a local server must construct in order to satisfy the customer's
request. Informally speaking, a presentation plan is a detailed (temporally
synchronized) sequence of steps that the host server must perform at given
points in time. This involves obtaining committments from other video servers,
obtaining committments from the network service provider, as well as making
committments of local resources, within the limitations of available
bandwidth, available buffer, and customer/client data consumption rates.
The three types of plans described in this paper all work at different
"levels of abstraction" in this planning process. Furthermore, we introduce
two measures of how good a plan is: minimizing wait time for the customer,
and minimizing a quantity called access bandwidth (which informally speaking,
specifies how much network/disk bandwidth is used). We develop algorithms
to compute optimal (w.r.t. the above measures) plans for all three types,
and show experimentally that in all three cases, one of the three types
of plans (called a hybrid presentation plan) systematically outperforms
the other two. In addition to these new concepts, our framework has the
advantage that many results that had previously been verified experimentally
in the literature can now be conclusively proved mathematically.
(Also cross-referenced as UMIACS-TR-96-91)