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Client-Server Assignment for Internet Distributed Systems. Overview. Introduction Problem Definition Problem Model Solution Conclusion. Introduction. Internet - Distributed System Example: Email,IMS. Features: 1 . Communication Load Clients assigned to two different servers.
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Overview • Introduction • Problem Definition • Problem Model • Solution • Conclusion
Introduction • Internet - Distributed System • Example: Email,IMS
Features: • 1. Communication Load • Clients assigned to two different servers. • Clients assigned to same server. • 2. Load Balancing • Use fewer servers. Servers are heavily loaded
Problem Definition • Optimal client server assignment for a pre-specified trade-off between load balance and communication load. • Emerging Applications: • Social networks Eg: Facebook • Distributed database system, Eg: MapReduce
Communication Model • Initially assign clients to a system with 2 servers (Sa, Sb) • Then we extend the 2-server solution to multiple servers. • Xi = 1, client i is assigned to Sa • Xi = -1, client i is assigned to Sb • : data rate from client i to client j.
Communication Load • if i and j are assigned to same server. • 2 if clients are assigned to 2 different servers. • Total communication load, • If i and j are assigned to different servers, • = -1
Load Balance • Load balance, D =
D can be expressed as, • Refer link • Adding D to objective function will make the function non-quadratic. • Hence we modify D,
Equivalent formula of D, • D = , • where • Refer link • As, = 1, • = • Refer link
Optimization problem: • Minimize: • Subject to : • Where: • = • is an arbitrary co-efficient (0≤≤1)
Objective function : • minimize • Where we define, • Refer link
Semidefinite Programming • Semidefinite programming is a class of convex optimization. • : set of real Symmetric matrices. • A matrix is called positive semidefiniteif , for all • It satisfies strict quadratic programming
Solution: • minimize: tr( • subject to: • Solution Matrix = • W-> Matrix with diagonal elements 0 and Wi,j • U -> symmetric & Positive semidefinite matrix
Conclusion • 1. Hard problems could be formulated as a optimization problem and solved. • 2. optimization problems, are widely used in tremendous number of application areas, such as transportation, production planning, logisticsetc.
Extra information: • Transform program into Vector program: • Minimize: • Subject to: = 1,
Vector programming -> Semidefinite programming • W-> Matrix with diagonal elements 0 and Wi,j • U -> symmetric & Positive semidefinite matrix • minimize: tr( • subject to:
Solution Matrix = • Cholesky Factorization: • Obtain V= ( • Satisfying . • Final solution: • Round n vectors (to n integers (