DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Networked Media LaboratoryDept. of Information & Communications

Gwang-ju Institute of Science & Technology (GIST)http://netmedia.gist.ac.kr

Optical Multicasting for Interactive Real-time Application in Sparse Splitting Optical Networks

Ju-Won Park, Hyunyong Lee, and JongWon Kim 2007/ 08/ 27

APAN Network Research Workshop 2007

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Contents

Introduction Related Work Constrained Optical Multicast Routing

Problem statement The proposed light-tree construction algorithm

Experiment Results Conclusion

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Introduction

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Multicast in IP over WDM Networks IP layer multicast Multicast via WDM unicast WDM layer multicast

Multicast tree constructed by the IP layer can make copies of a data packet and transmit a copy to each of its child Require O/E/O conversion

Undesirable Inefficient Long latency

Multicast over WDM networks

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

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 optical domain via light splitting (c) More desirable – transmission to different destinations can now share bandwidth on

common link Useful to support high-bandwidth multicast application such as HDTV.

WDM layer multicast potential advantages Knowledge of the physical topology – more efficient multicast routing is possible Light splitting is more efficient than copying packets Avoid the electronic processing bottleneck Support of coding format and bit-rate transparency across both unicast and multicast

Multicast over WDM networks

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Related Work

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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 to destination. 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 problem which is known to be NP-complete

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

Networks with Sparse Light Splitting,” in J. of Lightwave Technology, vol. 18, no. 12, December 2002.)

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

Delay boundary (M. Chen, S.Tseng, B. Lin, “Dynamic multicast routing under delay constraints in WDM networks with heterogeneous light splitting capabilities,” in Computer Communications 29 (2006) 1492-1503)

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Constrained Optical Multicast Routing

•Problem statement•The proposed light-tree construction algorithm

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Problem Statement Sparse splitting optical network

MC (multicast capability) node MI (multicast in-capability) node

We define a delay function which assigns a nonnegative weight to each link the network

To deliver interactive real-time application via light-tree, we consider three parameters

Adequate signal quality – power constraint

End-to-end delay boundary

inter-destination delay variation boundary

),(

)(vsHT

D

),( ),(

)()(vsH usHT T

DD

),(

)(vsTH

D

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Goal Every member of session is connected Satisfy the delay and inter-destination delay variation

tolerance Balanced tree to guarantee a certain level of optical signal

power

The way Adopt hierarchical approach

Constrained Optical Multicast Routing

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Constrained Optical Multicast Routing

Make multicast backbone network Build the auxiliary MC network as referred as multicast

backbone network, Every MC node is included. Adjacent MC node is connected using logical link if there is

available wavelength on the path. If there are multiple path between MC nodes, the shortest path is selected.

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

),(

),( )()(jiH

jiLT

MCLT

MCDHD

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Constrained Optical Multicast Routing

Physical Network(MC & MI network, G)

Multicast Backbone Networks

(MC network, G’)

Source of session 1

1

1

11

1

MC node

MI node

Source

Destination

1

1

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Constrained Optical Multicast 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 in multicast backbone network based on constraints.

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Constrained Optical Multicast Routing

Physical Network(MC & MI network, G)

Multicast Backbone Networks

Build the light-tree based on application requirement in MC network

(MC network, G’)

Primary MC Node of session 1

Source of session 1

1

1

11

1

MC node

MI node

Source

Destination

1

1

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Constrained Optical Multicast 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 in subset and then, join the light-tree by connection with selected MC node

),(

)()(),( kiLTMCLT HisH

DD

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Constrained Optical Multicast Routing

Physical Network(MC & MI network, G)

Multicast Backbone Networks

Build the light-tree based on application requirement in MC network

(MC network, G’)

Primary MC Node of session 1

Source of session 1

1

1

11

1

MC node

MI node

Source

Destination

1

1

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Completed light-tree meets the delay boundary with balanced aspect.

It does not satisfy the inter-destination delay variation boundary.

Reduce the inter-destination delay variation by swapping MI nodes

Constrained Optical Multicast Routing

),( ),(

max )()(maxvsH usHLT LT

DD

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Constrained Optical Multicast Routing

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Advantages Source need not know about the location of destinations.

Every destination need not find the minimum cost path from itself to source. It just must find the location of MC node which satisfies application requirement.

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

The procedure of dynamic addition or deletion of members 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 disconnected send the

prune message to connected MC node.

Constrained Optical Multicast Routing

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Experiment Results

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Experiment Results

The number of MI nodes

0 20 40 60 80 100 120 140

Inte

r-de

stin

atio

n de

lay

varia

tion

(ms)

40

60

80

100

120

140

160

180

200

220

240

Shortest path approachBalanced approach (LT0)Proposed approach

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Number of MI nodes

0 20 40 60 80 100 120 140

Max

imum

Spl

it R

atio

0

100

200

300

400

500Shortest path approachBalanced approach, proposed approach

Experiment Results

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Conclusion

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

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 the

feasible light-tree

Wavelength assignment algorithm should be explored in future research. Minimize wavelength cost

DEPT. OF INFO. & COMM., GISTNetworked Media Lab.

Q&A