Multicast NSR
Non-stop routing (NSR) is a reliability technology applied to a system with double control planes (for example, a device with double main control units). This technology shields switchovers between system control planes from the routing protocol control plane. When a switchover occurs between the main control units on a device, its neighbors are unaware of the switchover.
Only the AR6300 series support NSR.
Fundamentals
IP multicast services, such as IPTV, video conferencing, and tele-education, require high network reliability. Without the multicast NSR technology, multicast forwarding is interrupted if a device on a multicast network experiences an active/standby switchover.
Multicast NSR technology can ensure non-stop multicast forwarding during an active/standby switchover. When the standby main control unit starts, multicast NSR starts to back up multicast routing information and multicast protocol control information (including neighbor, multicast distribution tree, RP set, and user access information) to the standby main control unit. When a switchover occurs between the active and standby main control units, multicast data can still be forwarded according to the backup multicast routing information. In addition, the local device maintains the PIM neighbor relationships using the backup protocol control information so that neighbors are unaware of the switchover. Backup of multicast routing information and multicast protocol control information ensures non-stop multicast routing, delivering high reliability for multicast services.
Implementation
On IPv6 multicast networks, multicast NSR can be implemented for the Multicast Listener Discovery (MLD) and IPv6 Protocol Independent Multicast (PIM). Multicast NSR involves the following mechanisms:
Batch backup
When the standby main control unit starts, the active main control unit backs up all multicast routing information and multicast protocol control information to the standby main control unit, ensuring consistent information on the two main control units.
Real-time backup
During operation of multicast protocols, the active main control unit backs up changed multicast routing information and multicast protocol control information to the standby main control unit in real time, ensuring data synchronization between the two main control units.
Switchover
If the active main control unit fails, the standby main control unit takes over services. The standby main control unit saves the same multicast routing information and multicast protocol control information as the active main control unit, so multicast forwarding is not interrupted during the switchover.