Light Tree Final
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Transcript of Light Tree Final
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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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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 inmulticast backbone network based on constraints.
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Constrained Optical Multicast
Routing
Physical Network(MC & MI network, G)
Multicast Backbone Networks
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
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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Constrained Optical Multicast
Routing
Physical Network(MC & MI network, G)
Multicast Backbone Networks
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