15.4.4 IPv4 path control operation when IGMPv3 is used

<Structure of this section>

(1) IPv4 PIM-SSM operation when using IGMPv3

Sender information is needed to use PIM-SSM. The Switch allows PIM-SSM to be used by setting the sender during configuration when IGMPv2 is used. For IGMPv3, PIM-SSM can be used without setting a sender in the configuration (PIM-SSM needs to be set in the configuration).

IPv4 PIM-SSM operation is as follows when the multicast distribution server (source address S1) sends multicast packets to multicast group G1:

An IGMPv3 Report (G1, S1) to join the multicast group is received from hosts.
Switches receiving the IGMPv3 Report (G1, S1) compare the group address (G1) reported by the Report with the SSM group address (range) specified in the configuration. If the group addresses match, a PIM-Join message including the group address (G1) and source address (S1) is sent to the source address (S1) reported in the Report, over the shortest path.
The switches receiving the PIM-Join message forward the message to source address S1 hop-by-hop over the shortest path. These switches form an S1-to-G1 delivery tree so that multicast packets from source address S1 are forwarded only to the interfaces from which the PIM-Join message was received.

Switches receiving multicast packets sent by multicast distribution server S1 to group G1 forward the multicast packets based on multicast forwarding information.

Figure 15-19: Outline of IPv4 PIM-SSM Operation When Using IGMPv3

(2) IPv4 PIM-SM operation when using IGMPv3

If PIM-SSM is not configured, PIM-SM operation is performed. IPv4 PIM-SM operation is as follows when the multicast distribution server (source address S1) sends multicast packets to multicast group G1:

An IGMPv3 Report (G1, S1) to join the multicast group is received from hosts.
Switches receiving the IGMPv3 Report (G1, S1) send a PIM-Join message including the group address (G1) to the rendezvous point over the shortest path.
The rendezvous point receiving the PIM-Join message learns about the existence of the group. A delivery tree from the sender via the rendezvous point is formed so that multicast packets can be delivered from the sender network to each group member via the rendezvous point.
The shortest path from the sender to each group member is determined by using the existing unicast routing information (PIM-Join messages are sent to the sender over the shortest path to the sender to form a shortest-path delivery tree).

Switches receiving multicast packets sent by multicast distribution server S1 bound for group G1 forward the multicast packets based on the shortest path delivery tree.

Figure 15-20: Outline of IPv4 PIM-SM Operation When Using IGMPv3

(3) IPv4 path control when IGMPv1/IGMPv2 hosts and IGMPv3 hosts are mixed

The following explains IPv4 path control operation if PIM-SSM is set to be used on IGMPv2, and IGMPv1 hosts, IGMPv2 hosts, and IGMPv3 hosts are used together.

PIM-SSM operates when a membership request is received for a group address included in PIM-SSM target address range set in the configuration (see "IPv4 path control operation when mixing 15-13 IGMPv1/IGMPv2 and IGMPv3 hosts"). When a join request is received through an IGMPv1 Report or IGMPv2 Report, the sender list uses the source address set in the configuration. When a join request is received for the same group address through an IGMPv1 Report, IGMPv2 Report, and IGMPv3 Report (EXCLUDE), the used sender list combines the source addresses set in the configuration and the sender list contained in the IGMPv3 Report (INCLUDE).

The following table describes the IPv4 path control operations performed when IGMPv1/IGMPv2 and IGMPv3 hosts are used together.

Table 15-13: IPv4 path control operation when IGMPv1/IGMPv2 and IGMPv3 hosts are mixed
Subscription group addresses	IGMPv1 Report IGMPv2 Report IGMPv3 Report(EXCLUDE)	IGMPv3 Report(INCLUDE)
Within the SSM address range	PIM-SSM	PIM-SSM
Outside the SSM address range	PIM-SM	PIM-SM