opticalnetworks.pdf

7/29/2019 opticalnetworks.pdf

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OPTICAL MULTICAST ROUTING

Multicasting- Source communicates with with a set ofdestinations(one to many communication).

Applications of multicasting:

Video Conferencing,Distance Learning etc

Disadvantage of realising a multicast session byestablishing a unicast path between each source anddestination:

a.Many resources are required(distinct wavelength andwavelength channels)


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l

b.Source has to transmit the same data a number of

times which is equal to number of destinations.

To overcome these disadvantages nodes should have

the capability to tap and split an optical signal

Nodes with splitting capability is called multicast

capable nodes.It makes copies of data in optical

domain via optical ower splitting and forwardincoming data to more than one output link.


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Nodes without splitting capability are called multicast

incapable(MI) nodes.

DaC nodes or Drop and Continue nodes are such MI nodes

which tap a small amount of optical signal from a wavelength

channel while forwarding the data on that channel to an output

link.The tapped power is used by the node if it is the destination.

DoC nodes or Drop or Continue nodes are MI nodes which can

either drop a message or switch a message but not both.


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Wavelength conversion node (WC) is a DaC node with

wavelength conversion capability.

A Virtual souce is a split node and a WC node.

A light-tree is a wavelength continuous tree rooted at thesource connecting a set of destinations in all optical

network.It is needed to transmit a single message to different

destinations in WDM network.

If all the nodes are MC then network is referred as network

with full splitting capability.


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Else it is referred to as sparse light splitting network.

A virtual source can support moe than one connection on

the same outgoing link by using different wavelengths

unlike a simple MC node.Issues in constructing a multicast tree:

Minimise resources and setup time required for tree

construction.


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0

2

1

3 6

5

4 0 2

0

0

0

0

2

2

2

2

3

4

5

5 6

W0

W1

W0

W1

W2 W2

W3 W3

W4 W4 W4

l b.Multicast roting using unicast pathsa.Example network


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0 3

5

6

W0

2

W0

W0

W0

W0

W0

c.Multicast routing using split and tap capable nodes


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Node 0 is the source.

Node 2 and node 6 are the destinations

For using different unicast paths we need fivelightpaths as shown in b.

We also need 10 wavelength channels and the source

has to transmit data five times for the unicast

approach.


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In c we assume all nodes are MC and DaC.

Node 2 uses splitting capability to transmit optical signal

on link 0-2 to links 2-3,2-4 and

2-5.

Node 5 taps part of the signal and forwards the remaining

signal to 5-6.

Only one wavelength and 5 channels required.Node 0transmit only once.

opticalnetworks.pdf

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