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Experimental results and performance evaluations (3)
In case of multicast
distribution of the same VoD flow to multiple clients, the ubiQoS middleware
can significantly reduce the network traffic by exploiting the location awareness
typical of the MA programming paradigm.
In traditional VoD systems over networks that do not support IP multicast, the
VoD server is forced to generate N flows, one for each requesting client. The
ubiQoS processors can ascertain whether there are several receivers
interested in the same VoD flow within their served localities, can split
VoD flows only when necessary and can downscale the VoD quality depending on
the maximum QoS requirements in their distribution sub-tree. In a usage
scenario with clients that requested the same QoS level, ubiQoS achieves the
same traffic reduction of network-layer multicast support, without requiring
compliant hardware, e.g., IP-multicast routers. In case of different QoS level
requests, ubiQoS can even generate less network traffic than IP-multicast solutions.
In fact, instead of distributing one multicast flow for any different QoS request,
the ubiQoS infrastructure uses one unified VoD flow and dynamically downscales
it at the proper node in the active path, by exploiting its awareness of the
QoS levels requested in any distribution sub-tree.
A significant estimate of the network traffic generated by multicast distribution
is the overall traffic BT, defined as the total number of bytes
exchanged between any pair of adjacent nodes (client stubs-processors-server
stubs in ubiQoS, clients-routers-servers in traditional provision scenarios)
along the VoD distribution tree. We measured BT for different values of the
number N of intermediate nodes and with different locations of 9 multicast clients
requesting the same VoD content. Our testbed assumed that 3 clients requested
the VoD flow with gold QoS (original VoD format), 3 with silver
QoS (50% bandwidth saving via frame rate reduction), 3 with bronze
QoS (90% bandwidth saving via reduction of both frame rate and resolution).
Figure 4b
shows the average results for BTnorm
= BT / BTnoMulti
where BTnoMulti is the BT value for distributing the flow over a single path
segment with no multicast support.
The figure reports the experimental
results in case of VoD distribution with/without IP-multicast and by exploiting
the ubiQoS infrastructure. On the average, for N greater than 3, ubiQoS
reduces BT more than three times if compared with non-IP-multicast distribution.
Figure 4b. ubiQoS multicast network traffic.
Download
ubiQoS v1.0 (SOMA
v4.0 included) |
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(The full code -java source included- of the ubiQoS middleware and of the SOMA programming environment has been written in collaboration with external partners and cannot be distributed freely. However, contact us, specifying your name, your affiliation and the full code you are interested in, and we will try to provide you a copy only for educational purposes and non-commercial use)
