PROFITABLE CONNECTION

ASSIGNMENT IN ALL OPTICAL

WDM NETWORKS

VISHAL ANANDLANDER

(Lab. for Advanced Network Design, Evaluation and Research)

In collaboration with:Tushar Katarki and Chunming Qiao

CSE Dept., SUNY at Buffalo

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Introduction Related work Maximum Profitability Problem Concluding remarks Questions and discussion

Vishal Anand

Outline

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Introduction

Optical WDM networks - future backbone for wide area networks.

Physical Topology - Optical wavelength routers connected by fiber links.

Lightpath or connection - Path between two end nodes and a wavelength on that path.

No wavelength conversion - Any lightpath uses the same wavelength on all the links its path spans.

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The RWA(Routing & Wavelength Assignment) Problem Given :

– a network topology– a set of traffic demands (or connection

requests).

Determine the routes and wavelengths to use so as to satisfy the demands.

The RWA problem is usually solved to optimize some specified objective(s).

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Previous and related work

Example objectives – Minimize network-wide packet delay (e.g. number

of hops). – Maximize throughput (e.g. number of lightpaths). – Maximize allowable capacity upgrade or scalability

(for future traffic demands). Minimizing cost (network resources used) can

also be an important objective. For a bandwidth broker (or carrier) maximizing

profits is most important.Vishal Anand

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The Maximum Profitability Problem

Given:– a set of connection requests, N.– a network topology.

– earnings (revenue) Ei associated with each connection request, i.

– cost of using any wavelength on a link l, Cl.

Solve the RWA problem to maximize the profit, P = Total Earnings - Total Costs.

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Maximizing profit problem is a more general formulation.– If Ei=E, for each connection/lightpath i (i.e., all

connections have equal earnings) OR if n=N (i.e., all the connection requests have to be satisfied) then the problem is same as the minimizing cost problem.

– If Ei=E and if all connections/lightpaths have equal costs. Then the problem is the same as maximizing throughput problem.

Hence a more direct study of the maximizing profit problem is necessary.

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Network Model

Network topology considered: 16 node NSFNET.

Cost of using each wavelength on a link , is the same, but varies from link to link.

No wavelength conversion capabilities at any of the nodes.

Number of wavelengths on each link in the network is the same.

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Heuristic based approach

The RWA problem is known to be NP Hard and hence computationally intractable.

Maximizing profit heuristic: MaxPro– Find a cheapest path for each connection request

and compute the profit.– Sort the requests in the order of decreasing

profit and store in a list.– Satisfy connection requests in decreasing order

of profit (a greedy approach).– If a connection request is satisfied.

• delete that connection from the sorted list.

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– If the cheapest path for a connection request is not available.

• Re-compute a new cheapest path for only that connection request.

• Compute the new profit for this connection request. • Insert this connection into the sorted list depending

on the profit.

– Repeat till no other connection request can be satisfied.

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Results and Comparison

1) Results obtained from MaxPro compared with:– a minimizing cost heuristic– a random assignment heuristic

2) Results of Maxpro compared with the optimal results from integer linear program.

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Comparison of the heuristics

MaxPro performs the best. Better than a minimizing cost heuristic.

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Integer Linear Model

Definitions:– W :Number of wavelengths on each link.– n, L :Number of nodes, links in the network.– :Earnings obtained by satisfying a connection request between

nodes and . – : Total number of alternate routes/paths available to reach node

from node .

– : Cost of reaching node from node on route r.

– : = 1, if link j is used by the route r between nodes and , 0 otherwise.

– : Number of connection requests between nodes and .– : = 1, indicates that the connection between node and is

routed on route r using wavelength k. Vishal Anand

E

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Objective function

Subject to:

– The total number of lightpaths established between a node pair should not exceed the number of requests between that node pair.

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k

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And

– The total number of lightpaths established on any link should not exceed the number of wavelength on that link.

– A wavelength on a link can support at most one lightpath.

– The Integrality constraint.

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rkn n R

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rj ,...,1,,...,111 1 1

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Comparison of Maxpro with ILP

MaxPro obtains on the average 90% of the results got from the ILP(optimal profit).

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Summary and Future work Formulated a RWA problem with the objective of

maximizing the profit. Proposed a maximizing profit heuristic. Compared results of a profit maximizing heuristic

with a minimizing cost heuristic and ILP. Future work

– Study the maximizing profit problem for the On-line traffic model.

– Extend to cases where protection and restoration is required for the traffic.

Vishal Anand