Re: [pim] Simple join failure notification for PIM-SM multicast routing

[Jean-Jacques Pansiot <Jean-Jacques.Pansiot at crc.u-strasbg.fr>]

Dino Farinacci wrote:
> > > "Currently, PIM-SM is the most widely deployed multicast routing
> > > protocol in the Internet. However in IPv6 this multicast protocol
> > > lacks a simple connectivity debugging tool, making it difficult to
> > > identify multicast routing problems.  When a host wants to receive a
> > > multicast group or channel, if the corresponding  PIM-Join message
> > > cannot be propagated in the network, nothing exists to inform the
> > > receiver or the network about this failure. We propose a simple error
> > > notification message based on ICMP/ICMP6 which is able to indicate
> > > where and why the error happened in the network without using a
> > > multicast traceroute mechanism."
> > >       
>
>     IP multicast scales well today because no where in the network state is
>     maintained per receiver. This is an important scalability principle I
>     would like to see not change.
>
>     What happens if a link goes down where it affects 1000s of receivers.
>     The router on the downstream side of the failure would 1) have to track
>     the receivers and 2) send a message to each of them. This can't possibly
>     be workable. 
>   
this is not at all what we propose. No information on  receivers is 
maintained.
The unreachability message is sent to downstream routers,
using outgoing interfaces in the group/channel entry of the TIB (that is 
the same interfaces
it would send a data packet)

Jean-Jacques

>     This should be solved and there are cases where it has been solved by
>     doing beaconing at the application layer.
>
> Dino
>   


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