performance enhancement of optical wdm networks through improved (2)

8/8/2019 Performance Enhancement of Optical WDM Networks Through Improved (2)

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`MOTIVATION


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` Need+Promise=Challenge

` Need

` High Capacity Networks

` Mature switching and Routing techniques in optical networks

` Promise of Optical Technology

` Ultra Low Transmission Losses

` Ultra Wide Band

` Very High Bitrates

` Advantages of optical fibers over copper transmission line include the ability to carrysignals over long distances, low error rates, immunity to electrical interference, security,and light weight

` Challenge` Better algorithms of Routing and Wavelength assignment

` Better optical burst switching

` Better optical packet switching


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` INTRODUCTION


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` Fiber optics communication has provided us very high speed

communications with enormous bandwidth potential. Although fibers

can support very high data rates, the associated electronic processing

hardware will typically not be able to keep up with such speeds. Henceelectronic handling of data network nodes basically limits the

throughput of the network. Further, electronic processing is required

because optical storage and processing technologies are not mature

yet. Hence a packet that must be stored or processed at an

intermediate node has to be converted to its electronic form and stored

in an electronic buffer memory. The header is then extracted,processed and a routing decision is made based on the information

provided in the header and the routing protocol. The packet is then

queued at the output port, converted back into its optical form and

transmitted towards its final destination . To improve the throughput of

the network and to minimize transmission delay, the network

architecture must both reduce the number of times a message isprocessed by the intermediate nodes and must streamline the

processing at each node.


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Wavelength Division Multiplexing (WDM) is based on a well known conceptcalled Frequency Division Multiplexing orFDM [1]. With this technology, the

bandwidth of the channel is divided into multiple channels, and each

channel occupies a part of the larger frequency spectrum. In WDM network,

each channel is called Wavelength. This name is used because each

channel operates at a different frequency and at a different optical

wavelength.


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The process of WDM can be easily explained by the Figure. It shows a simple

example of a typical WDM link. Four fibers having different wavelengths (1- 4) are

connected to the WDM multiplexer, through transmitters which combine or multiplex

them onto the single fiber. The opposite operation occurs at the receiving de-

multiplexer, which separates the wavelength and sends them to an appropriate

output port, perhaps to the other fibers.


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x Routing and Wavelength Assignment

` To design a lightpath topology that interconnects the IP routers and to

realize this topology within the optical layer one should first meet the traffic

requirement. There are many problems which are faced in the development of

lightpath. The first problem which is faced is lightpath design [3] (LTD) problem.

Due to the limitation in the number of wavelengths available on each fiber link

as well as the wavelength-continuity constraint (in the absence of wavelength

conversion) [2], the Routing and Wavelength Assignment (RWA) problem has

been a crucial issue for achieving good network performance.` The Routing and Wavelength Assignment (RWA) problem is defined as: given a

network topology, a set of end-to-end lightpath requests, determine how to route

those requests, and which wavelengths they should be assigned using theminimum possible number of wavelengths


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Optical Switching

`

` Circuit switching is advantageous when we have constant data rate traffic (fixeddelays) in the network, like voice traffic; however, it is not suitable under bursty traffic

conditions, or when circuits are idle. Packet switching works well with variable-rate

traffic, like data traffic and can achieve higher utilization A possible near-term

alternative to all-optical circuit switching and all-optical packet switching is optical

burst switching.

` Although optical burst switching appears to offer advantages over optical circuit

switching and optical packet switching, several issues need to be considered before

optical burst switching can be deployed in working networks. In particular, these

issues include; network architectures problems in terms of the burst handling,

reservations techniques for efficient utilization of bandwidth as well as network

resources; burst dropping and contention resolution schemes supporting quality of

service, which need to be investigated in order to reduce congestion andpacket/burst loss in the high speed networks.


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`LITERATURE REVIEW


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` The main attention of this thesis will be on Routing

and Wavelength Algorithm problem. The Routing

and Wavelength Assignment (RWA) problem isdefined as;

for a given network topology, determine how to

route those requests and which wavelengths theyshould be assigned using the minimum possible

number of wavelengths [3].


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` The RWA problem can be solved either in one

phase, where both the route and wavelength is

assigned at the same time or in two phases,where first the routes are fixed and then a feasible

wavelength assignment is determined for the

given routing.


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` The RWA problems are divided into two

categories; Static RWA problem (also called off-

line RWA) and Dynamic RWA problem (also calledon-line RWA). Some of the steps for solving RWA

problem are considering RWA problem as a

whole, dividing RWA problem into sub problems,

the Integer Linear Program formulation, ILPformulation for virtual topology, getting the

Heuristic solutions, wavelength converter

placement.


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Paper Title Author Findings

Optical Networks A Practical

Perspective

Rajiv Ramaswami and Kumar N. Sivarajan Technology for packet to be queued at the

output port, converted back into its optical

form and transmitted towards its final

destination

Adaptive Routing Considering the Number

of available wavelengths in WDM Networks

Younghwan Yoo, Sanghyun Ahn and Chong

Sang Kim

Proposed four algorithms NAW, NUW_S,

NUW_U and Hop_NAW Algorithm. There

algorithms considered the availability of

wavelengths during the routing process.

These algorithms favor paths with near-

maximum number of available wavelengths

between two nodes, resulting in improved

load balancing

Routing, Wavelength and Time-Slot-

Assignment Algorithms for Wavelength-

Routed Optical WDM/TDM Networks

Bo Wen, Ramakrishna Shenai, and Krishna

Sivalingam

They proposed three algorithms; S-SP:

Sequential Shortest Path Algorithm, P-SP:

Parallelised Shortest Path Algorithm and I-

SP: Shortest Path Algorithm for improving

the obtained results.

Efficient Routing Technique for

Communication Networks

Jaspal Kumar, Muralidhar Kulkarni and

Daya Gupta

Proposed heuristic methods which were

based on (decomposed to) shortest path

searchesusing Dijkstras algorithm.

Routing and Wavelength Assignment in

Optical Mesh Networks with Wavelength

Conversion

A. Jaekel and T. Khan introduced a new integer linear program

(ILP) formulation for dynamic wavelength

allocation in survivable, wavelength

convertible WDM networks, using

dedicatedand shared protection

Static Routing and Wavelength Assignment

in Wavelength Routed WDM Networks

Nina Skorin-Kapov and Mladen Kos Deal with the problem of Routing and

Wavelength Assignment (RWA) of static

lightpath demands as a complete problem


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`GAPS


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` Several methods have been proposed for joint working and spare capacityplanning in survivable WDM networks. These methods consider a static trafficdemand and optimize network cost assuming various cost models andsurvivability paradigms. Some of the gaps are left in the researches:

` None of these approaches has been studied the incremental network upgrade

problem. Some ILP formulations have been studied in for the incrementalnetwork upgrade problem, but the ILP techniques have limitations in itsapplicability in large networks with huge traffic demands.

`

` The performance evaluation of the various routing algorithms for wavelengthdivision multiplexed networks has not been covered so far.

`

`

The wavelength converter have not been exploited yet.`

` The switching technique in optical networks has not been matured yet.

`

` Experimentation with the importance sampling with the first policy iterationapproach and other means to reduce the running time of the algorithm has notbeen covered so far.

`


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` Robustness of the algorithms deserves further study.`

` Another interesting (and endless) branch of possible studies which hasnot been covered is the RWA problem with various priori information

models about the traffic process such as known durations, differentdistribution for the duration etc. and any mixture of them.

`

` Techniques are required which can give accurate estimates fornetworks with first fit wavelength assignment when the number ofwavelengths is large. This is especially important, since for largecapacities, the first fit would yield much better throughput at lowblocking than random wavelength assignment.

`

` Another possible direction is to develop more accurate heuristics, oreven better, correct expressions for wavelength correlation betweenadjacent links which is insensitive to the direction in which we trace aroute while calculating blocking probabilities.

`


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` Development of an on-line RWA algorithm for network topologies other

than star and tree topology needs the further study.

` Development of heuristics for Multicast Routing and Wavelength

Assignment with multiple QoS demands needs the further study.Networks with limited splitting capabilities also need to be studied.

`

` Improvement of the linear programming method by exploring more

efficient ways to solve Mixed Integer Linear Programming (MILP)

problems. The linear programming method can be used in combination

with heuristic and other methods.

`

` The additional numerical studies are needed to compare the linear

programming solution with other methods that have been proposed for

WDM rings


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` Performance Enhancement of Optical WDMNetworks through Improved Routing and SwitchingTechniques The performance parameters are

x Latencyx Speedx Robustness

` new routing and wavelength assignment algorithmswhose performance will be better than the existingalgorithms

` Also new methods of devising control plane will bedeveloped or existing methods will be modified whichwill increase the performance of optical burst networks


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`OBJECTIVES


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`

` OBJECTIVES

` To study and compare existing routing and wavelength assignment

and switching techniques for Wavelength Division MultiplexedNetworks in terms latency, robustness and speed

` To develop new algorithms of Routing and Wavelength assignment

for better performance in Wavelength Division Multiplexed

Networks.

` To investigate appropriate switching technique based on opticalburst switching for Wavelength Division Multiplexed Networks.

` To investigate appropriate switching technique based on optical

packet switching for Wavelength Division Multiplexed Networks


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`METHODOLOGY


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` METHODOLOGY

` Comprehensive literature surveyof various existing routing and wavelength assignmentalgorithms for the wavelength division multiplexed networks.

`

` Analysis of various routing and wavelength assignment algorithms depending on the

various parameters.`

` Mathematical analysis will be conducted to gain insights which may not be obvious insimulation experiments. While simulation, it is often not clear whether all the importantparameter combinations have been covered or not, and often there are so many suchcombinations that simulating them all would be infeasible.

`

` Simulation will allow investigations of algorithms which are highly intractable from a

mathematical point of view. There are a number of simulation tools present which can beused for the simulation of routing algorithms. Some simulation tools such as MATLAB, C,C++ and VPI Transmission design suite will be used for simulation of the WDM networkand for the simulation of routing algorithm.

`

` Performance of various RWA algorithms is then evaluated. Comparison of various routingalgorithm will lead to the performance evaluation. Some parameters will be calculatedwhich will be responsible for the improvement of routing algorithms.

`

` Those parameters will be changed accordingly to get the best output of the routingalgorithm and a new improved routing algorithm will be developed.

`

` The new improved algorithm will be now compared with the existing algorithm so as toevaluate the performance of newly developed algorithm


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`PHASING OF

RESEARCH


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Duration Details of Work Agency/Person Involved

Aug-Dec 2010 Study of existing RWA algorithms and

making a comparative evaluation

Scholar, Guide

Jan-June 2011 Development of new routing and wavelength

assignment algorithms whose performance

will be better than the existing algorithms in

terms of the blocking probability

Scholar, Guide

July-Dec 2011 Testing and Improvements in the algorithms Scholar, Guide, TIE Patiala

Jan-June 2012 Study of existing Optical Burst Networks and

develop new protocols and new methods of

devising control plane

Scholar, Guide, TIE Patiala

Jul-Dec 2012 Study of existing Optical packet switched

networks and develop the packet size which

will cover all aspects of various layers adding

header and footers and which will make the

optical packet switching techniques to more

close to reality.

Scholar, Guide, TIE Patiala, NITTTR

Chandigarh

Jan-June 2013 Conclusion and Compilation of Thesis work

and present before the Panel

Scholar, Guide, TIE Patiala, NITTTR

Chandigarh and Punjab University


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`EXPECTED OUTCOME


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` Expected Outcome:

` The expected outcome will be in terms of the new routingand wavelength assignment algorithms whose

performance will be better than the existing algorithms interms of the blocking probability. The algorithms will takeless time and will be enhancing the performance of opticalnetworks.

` Also new methods of devising control plane will be

developed or existing methods will be modified which willincrease the performance of optical burst networks andwhose latency will be effective as compared to circuitswitching techniques.

` For packet switched networks , the packet size will be

developed which will cover all aspects of various layersadding header and footers and which will make the opticalpacket switching techniques to more close to reality.

performance enhancement of optical wdm networks through improved (2)

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