ITA Capstone
2016
Multicast vs. Unicast for Loss Tomography on Trees
ARL, IBM US, UMass, The Smith Institute for Industrial Mathematics and System Engineering (UK)
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Background on Tomography
Estimating Link Metrics
Network tomography provides a
methodology to infer internal network
characteristics through end-to-end
measurement between periphery
nodes.
Multicast:
Tomography On Tree Topologies
Unicast:
Use the root node and
leaf nodes as monitors, to
infer link states, i.e. loss
rate or delay
Multicast Vs. Unicast
Performance Comparison
Performance measure:
mean squared error over number of hops:
Results:
 Unicast outperforms multicast under tight probing budget
in terms of total number of hops traversed by probes,
especially when links have heterogeneous weights.
Multicast performs better when #hops is large. See Figure
1 and 2.
A multicast probe starts
from the root nodes,
traverses the whole
tree and is destined at
the leaf nodes.
Unicast traverses only
end-to-end paths.
Multiple unicast probes
are needed to cover the
whole tree.
 Multicast is more robust than unicast against different link
success distributions (Figure 3) and different tree sizes
(Figure 4).
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