Question regarding Multicasting

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Hi

Quick question about multicasting, that I hope someone can help me
with...unfortunately, I've never had any real life experience with it,
so am having a bit of difficulty visualising it.

Say I have a multicast group set up for 224.2.155.145. The source is
Host A, and the receivers are Hosts B, C, and D.

Does Host A send out three packets to the multicast IP address, knowing
in advance that 3 hosts are subsribed to it, or does it only send out
one packet that is somehow shared by the 3 hosts?

Thanks in advance.


Re: Question regarding Multicasting
Hi,

Host A will send out only one packet and will be received by host B,C, and
D. As such, it saves bandwith.

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Re: Question regarding Multicasting

Guan Foo Wah wrote:
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Thanks mate.


Re: Question regarding Multicasting
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And what important this one IP mcst packet is "cloned" in proper nodes in
internetwork.
The routers in the internetwork run multicast routing protocols, such us
PIM,
thanks to that they know where are the recievers for each mcst group.


Wlodek.




Re: Question regarding Multicasting


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Thanks Wlodek...where exactly are the packets cloned?


Re: Question regarding Multicasting
dilan.weerasinghe@gmail.com wrote:
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In the routers and switches!

Basically the point of multicastis to reduce traffic



Source
    |
--------------------------
  |          |         |
  |          |         R1
  |          |         |
  |          |         S1----Client2
  |          |         |
  |          |         Client1
  |          |        
  |          R2        
  |          |        
  |          S2
  |          |  
  |          Client3
  |            
  |          
  R3------------R4-----S4-Client4
  |
  S3-Client6
  |
  Client5

Assuming all clients want to Rx the group, R1 will forward each packet to S1.
S1 will duplicate it to Clients 1&2
R2 will forward t0 S2 which will forward to C3
R3 will duplicate to S3 and R4.
            R4 will forward to S4, to C4
            S3 will duplicate to C5&6.

That's 6 clients all get a copy of the packet from just one sent by the source.
--
Paul Matthews                          
paul@cattytown.me.uk
http://www.hepcats.co.uk

Re: Question regarding Multicasting

Paul Matthews wrote:
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Thanks for the excellent explanation, Paul.


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