Transcript Document 7691822

Constructing Efficient Overlays
• Problem formulation
– Given a set of
subscribers and a set
of machines,
distributed in the
Internet
– Construct an overlay
tree to minimize the
traffic/latency from
the event source to
the subscribers
Constructing Efficient Overlays (Cont.)
• Model 1
– Subscribers cannot relay traffic
– Restricted steiner tree
– Developed a new approximation algorithm with a
factor of 4.1
• Model 2 (p2p)
– Subscribers can relay traffic
– Minimum steiner tree problem
– Apply existing approximation algorithms
Load Balancing
• Given a set of machines
• Machine i can handle
Di rectangles as a dispatcher
or Si rectangles as a server
• Problem:
events
D
S
D
S
S
D
S
S
– Which set of machines are
servers, and which set of
machines are
dispatcher?
– How to assign server machines
to dispatcher machines?
• Objective function
min(max sj/Sj or dj/Dj)
Four Variations of the Problem
• Configured or not
– Whether each machine is already configured to be a
dispatcher or a server
• Unique or not
– Whether each server can only be assigned to a unique
dispatcher or multiple dispatchers
Configured
Unconfigured
Multi
O(n) Optimal
algorithm
Unique
NP complete:
Greedy 2-approx.
and PTAS algs
NP complete:
NP complete: work
Greedy 2-approx. in progress
Approaches
Optimization objective: min(max sj/Sj or dj/Dj)
Configured
Unconfigured
Multi
O(n) Optimal
algorithm
NP complete:
Greedy 2-approx.
Unique
NP complete:
Greedy 2-approx.
and PTAS algs
NP complete:
work in progress