All things related to multicast

[Simon Leinen <>]

>>>>> "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:

    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.