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Optical Multicasting for Interactive Real-timeApplication in Sparse Splitting Optical Networks


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CONTENTSINTRODUCTION

LIGHT PATH

WDM NETWORK

LIGHT TREE

SYSTEM MODELS

GENETIC ALGORITHM for WDM MULTICAST

PROBLEMCONSTRAINED OPTICAL MULTICAST ROUTING

RELATED WORK

CONCLUSION & FUTURE WORK


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INTRODUCTION Today, there is a general consensus that, in the near future, wide area

networks (WAN)(such as, a nation wide backbone network) will be

based on Wavelength Division Multiplexed (WDM) optical networks.

Depending on the underlying physical topology networks can beclassified into three generations:

First Generation: these networks do not employ fiber optic technology;instead they employcopper-based or microwave technology. E.g. Ethernet.

Second Generation: these networks use optical fibers for data transmission

but switching is performed in electronic domain. E.g. FDDI. Third Generation: in these networks both data transmission and switching

is performed in optical domain. E.g. WDM.


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The network traffic i.e, the messages or the packets transferred over the

network can be of three types ::

UNICAST TRAFFIC - Unicast traffic is sent from a single source to a singledestination IP address.

BROADCAST TRAFFIC - Broadcast traffic uses a special IP address to senda single stream of data to all of the machines on the local network. A

broadcast address typically ends in 255 (for example, 192.0.2.255) or has 255in all four fields (255.255.255.255).

MULTICAST TRAFFIC - Unlike unicast addresses, when a data stream issent to one of these addresses, potential recipients of the data can decide

whether or not to receive the data. If the user wants the data, the user'smachine receives the data stream; if not, the user's machine ignores it.


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LIGHT PATHA light path is an all-optical channel, which may be used to carry

circuit switched traffic, and it may span multiple fiber links.

A light path can create logical (or virtual) neighbors out of nodes that

may be geographically far apart from each otherA major objective of light path communication is to reduce the number

of hops a packet has to traverse

Under light path communication, the network employs an equalnumber of transmitters and receivers because each light path operates

on a point-to-point basis.


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WDM NETWORK There are two types of architectures of WDM optical networks: single-

hop systems and multi-hop systems [2].

Single-hop systema communication channel should use the same wavelength throughout the

route of the channel Multi-hop system

a channel can consist of multiple light-paths and wavelength conversion isallowed at the joint nodes of two light-paths in the channel.

In this paper, we consider single-hop systems, since all-optical

wavelength conversion is still an immature and expensive technology.(no wavelength conversion)


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Multicast over WDM networks Construct a virtual topology consisting of a set of lightpaths

from the multicast source to each destination (b) Using multiple unicasts

Inefficient bandwidth large multicast session

WDM switches make copies of data packets in the opticaldomain via light splitting (c)

More desirable transmission to different destinations can nowshare bandwidth on common link

Useful to support high-bandwidth multicast application such asHDTV.

WDM layer multicast potential advantages

Knowledge of the physical topology more efficient multicastrouting is possible

Light splitting is more efficient than copying packets

Avoid the electronic processing bottleneck

Support of coding format and bit-rate transparency across bothunicast and multicast


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LIGHT TREE A light tree is a point to point multipoint all optical channel, which

may span multiple fiber links.

Light tree enables single-hop communication between a source nodeand a set of destination nodes.

Thus, a light tree based virtual topology can significantly reduce thehop distance, thereby increasing the network throughput.


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System Models WDM network

Connected and undirected graph G(V, E, c)

V: vertex-set, |V|=n

E: edge-set, |E|=m

Each edge e in E is associated with a weight function

c(e): communication cost


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System Models

Cost of path P(u,v):

A multicast request in the system are given, denoted by r (s, D)

source s destination: D={d1, d2, ..., d|D|}

),(

)()),((vuPe

ecvuPc


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System Models This paper assumes an input optical signal can only be forward to an

output signal at a switch.

Tk (s, Dk) be the routing tree for request r (s, D) in wavelength k,where k


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Objective The cost of the tree

where yj =1 if wavelength j is used; yj=0, otherwise

Special case: One objective of the multicast routing is to construct a routing tree

(or forest) which has the minimal cost. The problem is regarded asthe minimum Steiner tree problem,which was proved to beNP-hard.

Anotherobjective is to minimize the number of wavelengths used inthe system.

In a single-hop WDM system, two channels must use differentwavelengths if their routes share a common link, which is thewavelength conflict rule.

y)()),((K

1j

j

),(

DsTe

i

ecDsTc


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Genetic Algorithm for WDM Multicast

Problems

7 9 10 12

4

5

8

13

14 1

2 113

15

16 17 6

6 3

5

4

6

1

9

4 10

7

115

8

2

2

3

5

6 3 1

4

4

12

6

7

3

1 3

2

r(s, {1,2,3,4,5,6})


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p1 p2 p3 p4 pi P|D|

Chromosome Encoding


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Light-Forest Construct Algorithm

Path by path construct

Integrated the path and wavelength in single phase

Step 1: Sort paths in increasing order according to the cost of each pathO(|D| log |D|) time. Assume that p1,p2,...., p|D| be the new index.

Step 2: p1 is assigned to wavelength 1,w=1, T1={p1}, T2= ...=Tk=. O(n)


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Light-Forest Construct Algorithm

Step 3: For i= 2 to |D] do Begin

j=1 while jw do

{ if pi is not conflict with Tj

then {assigned pi to Tj Tj=Tjpi flag=TRUE}

else j=j+1 } if f lag is not TRUE

then w=w+1 Tw=Tw pi

End


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s

7 9 10 12

4

5

8

13

14 1

2 11 3

15

16 17 6

6 3

5

4

6

1

9

4 107

115

8

2

2

3

5

6 3 1

4

4

12

6

7

3

1 3

2

Example

p1=s71 (10)p2=s7142 (13)p3=s9133 (15)p4=s104 (8)

p5=s

10

4

5 (12)p6=s91356 (26)

cost=8+10+4+15+13+26+2*


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Constrained Optical Multicast

Routing

Make multicast backbone network

Build the auxiliary MC network as referred as multicastbackbone network, Every MC node is included.

Adjacent MC node is connected using logical link if there is availablewavelength on the path. If there are multiple path between MCnodes, the shortest path is selected.

The delay of logical link is equal to the delay summation of path

),(

),()()(

jiH

jiLT

MCLT

MCDHD


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CONSTRAINED OPTICAL MULTICAST

ROUTING

Multicast Backbone Networks

(MC network, G)

Source of session 1

1

1

11

1

Physical Network(MC & MI network, G)

MC node

MI node

Source

Destination

1

1


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Routing

Build the light-tree based on application requirement

Source searches the MC node which is nearest from source as

referred to primary MC node. The primary MC node is unique of each session

Build the light-tree which has primary MC node as root inmulticast backbone network based on constraints.


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Routing



Build the light-tree based on applicationrequirement in MC network

(MC network, G)

Primary MC Nodeof session 1

Source of session 1

1

1

11

1MC node

MI node

Source

Destination

1

1


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Routing Each destination selects a adequate MC node

The MC selection by receiver is a key to construct feasible light-tree

Each MI node finds the subset of on-tree MC nodes which satisfy

the delay boundary

MI node chooses the MC node which has minimum fanout insubset and then, join the light-tree by connection with selectedMC node

),(

)()(),(

kiLTMCLTHisH

DD


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Routing



Build the light-tree based on applicationrequirement in MC network

(MC network, G)

Primary MC Nodeof session 1

Source of session 1

1

1

11

1MC node

MI node

Source

Destination

1

1


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Constrained Optical Multicast RoutingAdvantages

Source need not know about the location ofdestinations.Every destination need not find the minimum cost path from

itself to source. It just must find the location of MC nodewhich satisfies application requirement.

Simple construction of member-only light-treeThe procedure of joining the light-tree is only performed at

member.

The procedure ofdynamic addition or deletion ofmembers in a group is simple.Join: The node which wants to join in the multicast session

can be connected to its nearest MC node.

Leave: The node which wants to leave can be disconnectedsend the prune message to connected MC node.


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Related Work The main mechanism of transport over optical network is light-

path, a point to point all optical channel connecting from source todestination.

To incorporate optical multicasting capability, a light-tree, light-forest concept is introduced.

The problem of constructing a light-tree that spans a given source

and a set of destinations is similar to the Steiner tree problemwhich is known to be NP-complete

Consider several new issues and complexities for QoS provisioningof optical multicasting Sparse splitting (X. Zhang, J. Wei and C. Qiao, Constrained Multicast Routing in

WDM Networks with Sparse Light Splitting, inJ. of Lightwave Technology, vol. 18,no. 12, December 2002.)

Power constraint (Y. Xin and G. Rouskas, Multicast routing under optical layerconstraints, In Proc. of INFOCOM 2004)

Delay boundary(M. Chen, S.Tseng, B. Lin, Dynamic multicast routing underdelay constraints in WDM networks with heterogeneous light splittingcapabilities, in Computer Communications 29 (2006) 1492-1503)


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Conclusion & Future Work To support multicast in optical network

a balanced light-tree to guarantee signal quality

Delay and inter-destination delay variation along all source-destination paths in the tree should be bounded in sparse

splitting optical network.

The proposed algorithm is heuristic approach to obtain thefeasible light-tree

Wavelength assignment algorithm should be explored in futureresearch.

Minimize wavelength cost


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THANK YOUPRESENTED BY

ARNAB GUHA ROY

075157

SK SHAMIULLAH075155

DIBAKAR SAR - 075156

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