HP 6125XLG R2306-HP 6125XLG Blade Switch IP Multicast Configuration Guide - Page 153

Assert To eliminate these weaknesses, IPv6 PIM-SM allows an RP or the receiver-side DR to initiate a switchover to SPT: • The RP initiates a switchover to SPT: After receiving the first (S, G) multicast packet, the RP immediately sends an (S, G) source-specific join message hop by hop toward the IPv6 multicast source. The routers along the path from the RP to the IPv6 multicast source constitute an SPT branch. The subsequent IPv6 multicast data for the IPv6 multicast group can be forwarded to the RP along the branch without being encapsulated in register messages. For more information about the switchover to SPT initiated by the RP, see "IPv6 multicast source registration." • The receiver-side DR initiates a switchover to SPT: After receiving the first (S, G) multicast packet, the receiver-side DR immediately initiates a switchover to SPT as follows: a. The receiver-side DR sends an (S, G) source-specific join message hop by hop toward the IPv6 multicast source. The routers along the path from the RP to the IPv6 multicast source create an (S, G) entry in their forwarding table to constitute an SPT branch. b. When the multicast packets for the IPv6 multicast group are forwarded to the router where the RPT and the SPT branches, the router drops the multicast packets that reach it along the RPT and sends a prune message with the RP bit hop by hop to the RP. After receiving the prune message, the RP forwards it toward the IPv6 multicast source (supposed only one receiver exists). Thus, the switchover to SPT is completed. c. Finally, the IPv6 multicast source sends the multicast packets for the IPv6 multicast group to the receiver along the SPT. With the switchover to SPT, IPv6 PIM-SM builds SPTs more economically than IPv6 PIM-DM does. IPv6 PIM-SM uses a similar assert mechanism as IPv6 PIM-DM does. For more information, see "Assert." IPv6 administrative scoping overview Typically, an IPv6 PIM-SM domain contains only one BSR, which is responsible for advertising RP-set information within the entire IPv6 PIM-SM domain. The information about all IPv6 multicast groups is forwarded within the network that the BSR administers. This is called the "IPv6 non-scoped BSR mechanism." To implement refined management, you can divide an IPv6 PIM-SM domain into an IPv6 global-scoped zone and multiple IPv6 administratively-scoped zones (admin-scoped zones). This is called the "IPv6 administrative scoping mechanism." IPv6 administrative scoping mechanism The administrative scoping mechanism effectively releases stress on the management in a single-BSR domain and enables provision of zone-specific services through private group addresses. An IPv6 admin-scoped zone provides services for particular IPv6 multicast groups with the same scope field value in their group addresses. Zone border routers (ZBRs) form the boundary of an IPv6 admin-scoped zone. Each IPv6 admin-scoped zone maintains one BSR to provide services for IPv6 multicast groups with the same scope field value. IPv6 multicast protocol packets, such as assert messages and BSMs, of these IPv6 multicast groups cannot cross the boundary of the IPv6 admin-scoped zone that provides services for the group range. The IPv6 multicast group ranges to which different IPv6 146