All things related to multicast

[Marshall Eubanks <>]

Simon Leinen wrote:
> 
> >>>>> "bn" == Bill Nickless 
> >>>>> <>
> >>>>>  writes:
> > PIM-SM SNOOPING/SPOOFING ETHERNET SWITCH
> > ========================================
> > Consider a Gigabit/10-Gigabit Ethernet switch that is PIM aware.  It
> > could set up appropriate hardware forwarding based on the PIM Joins
> > sent between pairs.  Note that the hardware forwarding would have to
> > maintain separate (S,G) packet replication states for each peer that
> > has been asked for data by some other peer.  That is, the exchange
> > point switch won't get to pick an RPF towards each (S,G), so it will
> > have to maintain separate (S,G,RPF-port) states with distinct output
> > interface lists.
> 
> > Benefits:  - Peers get traffic only for (S,G)s they care about
> >             - Peers send only one copy of traffic for (S,G)s and
> >               the exchange point does the packet replication.
> >             - Peers get to choose (by their own policy) the best
> >               RPF for a given (S,G).
> 
> > Drawbacks: - Not yet available in the marketplace (to my knowledge).
> 
> Foundry does this starting with their software release 7.02.01.
> It seems to look only at the Gs, not at the (S,G)s(?).
> >From the release notes:

That is correct. Of course, an interdomain PIM snooping switch
should only look at (S,G), so this could lead to unwanted traffic, but
it's better than simple flooding.

I believe that Nitin Jain of Foundry has plans to implement full (S,G)
snooping in the near future. 

                    Regards
                    Marshall Eubanks

> 
>     PIM SM Traffic Snooping
> 
>     By default, when a Foundry Layer 2 Switch receives an IP multicast
>     packet, the device does not examine the multicast information in
>     the packet. Instead, the device simply forwards the packet out all
>     ports except the port that received the packet. In some networks,
>     this method can cause unnecessary traffic overhead in the
>     network. For example, if the Foundry Layer 2 Switch is attached to
>     only one group source and two group receivers, but has devices
>     attached to every port, the Layer 2 Switch forwards group traffic
>     out all ports in the same broadcast domain except the port
>     attached to the source, even though there are only two receivers
>     for the group.
> 
>     PIM SM traffic snooping eliminates the superfluous traffic by
>     configuring the Layer 2 Switch to forward IP multicast group
>     traffic only on the ports that are attached to receivers for the
>     group.
> 
>     PIM SM traffic snooping requires IP multicast traffic reduction to
>     be enabled on the device. IP multicast traffic reduction
>     configures the device to listen for IGMP messages. PIM SM traffic
>     snooping provides a finer level of multicast traffic control by
>     configuring the device to listen specifically for PIM SM join and
>     prune messages sent from one PIM SM router to another through the
>     Layer 2 Switch.
> 
>     NOTE: This feature applies only to PIM SM version 2 (PIM V2).
> 
>     [...]
> --
> Simon.

-- 


                                   Regards
                                   Marshall Eubanks


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