multicast-domain switch-without-register

Usage Scenario

In previous implementation, if the Switch-Group address is in the ASM address range, when the SPT switchover occurs on the multicast tunnel of the public network, the source PE sends the switchover message to all receiver PEs. After receiving the switchover message, these receiver PEs send the (*, G) Join messages to the RP of the public network to establish the RPT. When the Switch-Group address is used in the VPN to encapsulate multicast data, the public network side of the source PE receives the data forwarded from the VPN based on the Switch-Group address. Then the forwarding entries are created on the source PE, and the source PE encapsulates the data in the Register messages which are sent to the RP of the public network. Then, the RP decapsulates the Register messages, and sends the data to the receiver PEs. Finally, the receiver PEs trigger the SPT switchover towards the source PE. In this manner, the SPT is established on the public network.

When there are many entries involved in SPT switchovers, the speed of sending Register messages is reduced. As a result, sending the first Register message to the RP takes a long time for certain entries, and establishing the SPT on the public network is delayed. In addition, in the process of establishing the SPT on the public network, multicast services are interrupted and certain VPN data may also be discarded, leading to the service interruption on the user end.

To address the preceding problems, disable the source PE from sending the null Register message to the RP and establishing a public network SPT before the Switch-Group address is used to encapsulate VPN data.

Prerequisites

A Share-Group has been configured using the multicast-domain share-group binding command.

Configuration Impact

After the VPN data traffic exceeds the upper limit, the source PE uses the Switch-Group address to encapsulate data and sends the switchover message to the receiver PEs. If the Switch-Group address is allocated for the first time, when sending the switchover message, the source PE sends the Register message that is encapsulated with the VPN Hello message to the RP, and the RP forwards the Register message to the receiver PEs. Based on the received messages, the receiver PEs and the RP directly send the (S, G) Join messages to the source PE and establish the SPT on the public network in advance. In this manner, when the public network tunnel is switched from the RPT to the SPT, the number of discarded multicast messages is reduced and the impact on multicast services is minimized.