Subject: RE: [magma] Multipoint-to-multipoint PIM-SM

From: James Lingard <[email-masked]>
Date: Thu, 18 Nov 2004 18:16:00 -0000

-----Original Message-----
From: Tiago Duarte (Ext_PDM&FC LDA) [mailto:[email-masked]]
Sent: 18 November 2004 16:42
To: Gorry Fairhurst
Cc: [email-masked]
Subject: RE: [magma] Multipoint-to-multipoint PIM-SM

> > 1) You could have continuous presence for all speakers - that 
> > is everyone sees everyone else all of the time.
> >
> > In PIM_SM (ASM), all you need is one group address (*,G), and 
> > each site simply sends their video bit stream to their upstream
> > router with the address of the Group and Join the Group to
> > receive. Receivers join to the Group, and then as the network
> > discovers the sources for each group, joins each in turn (Sn,G).
> 	
> The point is, if the receivers starts to use source trees, how
> they discover new senders? If they just prune (*,G) and join all (Sn,G).

If the receiver has joined (*,G), then even though its local router may
switch to using source-based trees, the router will still remain on the
shared (*,G) tree.  That is, the router will join (Sn,G) and prune
(Sn,G,rpt), so it will stop receiving (Sn,G) traffic over the shared tree,
but it won't prune (*,G).

Therefore, new senders are discovered just as usual.

James.

-- 
James Lingard
Data Connection Ltd (DCL)
http://www.dataconnection.com/

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