PIM-SM Application in a Single AS
Figure 4-18 shows multicast services deployed on a large-scale network. The Interior Gateway Protocol (IGP) protocol is running on the network and all network segments are reachable. Multicast group members are sparsely distributed. Hosts on this network want to receive VoD information, and network bandwidth needs to be used efficiently.
Implementation Plan
As shown in Figure 4-18, HostA, HostB, and HostC are receivers of multicast video streams. The entire PIM domain runs PIM-SM. RouterA connects to multicast source S1 and RouterC connects to multicast source S2. RouterB connects to the network segment of HostA; RouterE and RouterG connect to the network segment of HostB and HostC.
The network deployment must meet the following requirements:
PIM-SM is enabled on all router interfaces.
As shown in Figure 4-18, the core device closest to the multicast source is used as the C-RP because multicast sources are densely distributed. The interfaces of RouterC and RouterD are configured as the C-BSR and C-RP. The BSR and RP are elected dynamically.
Recommended RP deployment is as follows:
On small- and medium-scale networks, a static RP can be used because the static RP is stable and has low requirements for device configurations.
If there is only one multicast source, a device directly connected to the multicast source can be used as a static RP so that the source DR does not need to register with the RP.
If a static RP is deployed, all routers including the RP in the same domain must be configured with the same RP information and the same range of multicast groups.
On large-scale networks, a dynamic RP can be used because a dynamic RP is highly reliable and easy to maintain.
If multiple densely distributed multicast sources exist on the network, a core device close to the multicast sources is used as the C-RP. If there are multiple densely distributed group members, a core device close to the group members is used as the C-RP.
To ensure consistent RP information on all devices in the PIM domain, use the same type of RP (static or dynamic) on all the devices.
IGMP runs between the routers and hosts on a shared network segment (between RouterB and HostA, and between RouterE/RouterG and HostB/HostC).
All router interfaces on the same network segment must run the same IGMP protocol version and be configured with the same parameters, such as the interval for querying IGMP packets and hold time for memberships. If IGMP versions or parameters are inconsistent, IGMP member relationships on routers are different.
After the network is deployed, HostA, HostB, and HostC send Join messages to the RP based on service requirements, and multicast source information can reach the receiver.
It is recommended that members be statically added to a multicast group at the network border. This improves the stability of multicast services.
