Upstream Activation for PIM-SM Fast Re-Route
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Solution Overview
Problem
PIM-SM's single multicast tree lacks redundancy for re-routing multicast traffic in case of network failures, leading to slow failure reaction times, especially in real-time applications, and existing fast re-route mechanisms like MoFRR and MRT incur unnecessary bandwidth usage due to always-active secondary paths.
Innovation Solution
Implementing an upstream activation mechanism that uses pre-computed secondary paths only when network failures occur, with downstream fast notification packets (DFNPs) processed in the dataplane to quickly reroute multicast data traffic and reduce bandwidth consumption by keeping secondary paths standby until needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If secondary paths are always active to provide immediate failover capability, then reliability is improved, but bandwidth consumption increases due to unnecessary traffic on standby paths
Solution Approach 1:
The patent implements dynamic path activation where secondary paths transition between standby and active states based on failure conditions. The system maintains pre-computed secondary paths in a dormant state during normal operation, then activates them dynamically when failures are detected through fast failure detection mechanisms, optimizing both reliability and bandwidth efficiency.
Solution Approach 2:
The patent pre-computes and prepares secondary paths in advance before failures occur, storing routing information and path metrics ready for immediate activation. This preliminary preparation ensures that when failures are detected, the switch to secondary paths can happen instantly without computation delays, maintaining both high reliability and low bandwidth consumption.
2Adaptability or versatility
If PIM-SM depends on unicast routing for multicast path determination, then routing flexibility is improved, but failure reaction time worsens because multicast recovery must wait for unicast routing convergence
Solution Approach 1:
The patent segments the routing function into two independent parts: unicast routing for control plane operations and pre-computed multicast-specific secondary paths for data plane fast failover. This segmentation allows multicast failure recovery to proceed independently of unicast routing convergence, achieving fast failover while maintaining routing flexibility through the pre-computed path structure.
Solution Approach 2:
The patent performs preliminary computation of secondary multicast paths in advance, storing them in the forwarding plane. When failures occur, the system immediately activates these pre-computed paths without waiting for unicast routing convergence, thus achieving fast failure reaction while maintaining the adaptability benefits of PIM-SM's unicast-dependent routing.
3Device complexity
If a single multicast tree is used to distribute content, then network simplicity is improved, but redundancy for re-routing during network failures is lost
Solution Approach 1:
The patent pre-computes secondary paths along the single multicast tree structure, storing alternative routing information in the forwarding plane. This approach maintains the simplicity of a single tree structure while preparing redundant paths in advance, enabling fast failover without requiring complex dual-tree architectures or increasing overall network structural complexity.
Solution Approach 2:
The patent introduces a fast failure detection and activation mechanism as an intermediary layer between the single multicast tree and the underlying network infrastructure. This intermediary rapidly detects failures and activates pre-computed secondary paths, providing re-routing capability without requiring changes to the fundamental single-tree network structure.
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3C
AI summary
An upstream activation mechanism provides enhancements to PIM-SM based fast re-route in a multicast communication network, where secondary paths provides redundancy to a multicast tree and are on standby to reduce bandwidth usage when there is no failure in the network. Upon receiving an indication of a loss of connection to the primary path of the multicast tree network, a network node that has a failure-free secondary path to a common source node of the multicast tree sends an activation packet upstream toward the common source node via the failure-free secondary path. The activation packet causes one or more upstream nodes to unblock their respective outgoing interfaces to thereby activate transmission of the multicast data traffic on the failure-free secondary path.