Multi Casting Cb Tvs Pim

8/11/2019 Multi Casting Cb Tvs Pim

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PAPER OVERVIEW:

!Evaluation of two Multicasting protocols namely CBT and PIM.

!Comparison of protocols in terms of End-to-end delay, Networkresource usage, Join time, Size of the tables containing multicast

routing information, and the impact of the timers introduced by

the protocols.

!Network Simulation tool OPNET is employed.

!Suggestions given to Improve PIM Sparse Mode.

MULTICASTING

!Multicasting is a communication service that allows an

application to efficiently transmit copies of a data packet to a set

of receivers who are multicast group members.

!Purpose of Multicasting Routing is to reduce cost for applications

that send same data to Multiple recipients.

!Performed by a multicast-capable virtual network called

Multicast Backbone.


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Uses of Multicasting.

!Audio and Video Conferencing

!Distributed Interactive Simulation

!Exchanging experimental data and weather map

MULTICAST ROUTING PROTOCOLS:

Approaches:

SOURCE BASED TREES!Uses a tree, specific to a particular sender and group.

!Uses shortest path tree routed at a sender.

!Ex: Core based Tree(CBT),PIM Sparse Mode Source Based

Tree(PIM-SBT)

SHARED TREES

!Uses a single center-based tree or core based tree to route traffic

from all senders to the group

!Uses shortest path tree routed at one or more predefined nodes in

the network called Core nodes

!Ex: PIM Dense Mode, PIM Sparse Mode Shared Tree(PIM-ShT)


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CORE BASE TREES(CBT)

!CBT is based on single shared tree for every multicast groupactive in the network.

!A join message is sent by a multicast router toward the Core node

via the shortest path.

!and a tree routed at the core is constructed as the

acknowledgements of the join message are processed

! When a node on the tree receives a packet addressed to the group

it forwards copies of the packet on all branches of the groupstree except for the branch on which packet arrived.


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PIM DENSE MULTICASTING ROUTING PROTOCOL

!Floods the network with data packets to set up a source based tree

for every sender to every group! Initially they send out packets to every potential receiver in the

network

!Any router which has no active members of the multicast group

for which the data was sent out sends prune messages towards

the senders to remove unwanted branches from trees for that

particular multicast group

!The data packets are again sent out to that router once the prunedinterface times out


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PIM SPARSE MULTICAST ROUTING PROTOCOL

A node in the network called Rendezvous Point(RP) is

assigned to the group RP is the center node of a directed shared tree for that group

When a multicast router learns via IGMP that a local host has

joined group G it sends a join message along the shortest path

to the RP of that group

A directed source based tree is built from the sender to the RP

by the RP

TWO TYPES OF PIM SPARSE TREES

Shared tree case of PIM SPARSE(PIM ShT)

Source Based Tree case of PIM SPARSE(PIM-SBT)


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Shared Tree Case of PIM SPARSE(PIM-ShT)

Any sender to a particular Multicast group sends the packet to

the RP of that group The RP then sends the packets to all the members of the

multicast group of which its the RP

A source based tree for sender S is built between the source S

and the Rendezvous Point(RP)

The shared tree is built which is directed away from the RP

towards all the receivers of the group


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SOURCE BASED TREE of PIM SPARSE (PIM SBT)

A receiver learns of senders to a group when it receives datapackets on the tree directed away from the RP

The receiver then sends join messages towards specific senders

to become part of a shortest path,source based trees routed at

those senders

The receiver also alerts routers on the shared tree such that no

packets from these sources are forwarded to it


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SIMULATION ENVIRONMENT

The protocols(CBT,PIM DENSE,Shared case of PIM Sparse

and Source Based tree case of PIM Sparse) were simulatedusing the OPNET network simulation tool

TOPOLOGIES CONSTUCTED USING OPNET:

AAI/MAGIC/ATDnet

HIGH BANDWIDTH MESH TOPOLOGY LOW BANDWIDTH MESH TOPOLOGY


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OVERHEAD TRAFFIC PERCENTAGE

!Percentage of Total Number of bits trasmitted.

!CBT has the lowest overhead.


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TRAFFIC CONCENTRATION

!Measure of the distribution of the total n/w traffic on all links.

!PIM Dense distributes traffic more evenly.

!Helps to figure out locations of probable Cores and RP's.

JOIN TIME

!Time elapsed between, a host asking to join the group and the

time it receives it'e first message.

!PIM Dense join times are much higher than those of other

protocols for every network


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SUGGESTIONS FOR PIM SPARSE

!Decision as to whether the Source-Based tree or Shared Treemode be used should be made by the Initiator rather than

individually by the receivers.

!For Shared Tree group, There is no need for senders to register at

the RP or to have source based routes from the sender to the RP.

They can directly use the shared tree.

!Operations of Source Based Tree could follow these steps:

- A receiver sends a Join message to RP.- RP sends the current list of senders for a group back

to the receiver.

- New sources register with RP.

- RP multicasts the arrival of new member.

- RP periodically transmit a list of senders to the group.

Thus

Intricacy's of PIM protocol is greatly reduced.

Number of Timers required are reduced.


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CONCLUSIONS

Experimental results are summarized.


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Multi Casting Cb Tvs Pim

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