Multicast Tree Switchover via Forwarding Plane Thresholds
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Solution Overview
Problem
Existing methods for switching multicast data flows from a shared distribution tree to a shortest path distribution tree in a multi-process environment are inefficient, leading to high latency and increased messaging between the control plane and forwarding plane of routers, which does not scale well with large numbers of source group entries.
Innovation Solution
A method where byte counters in the forwarding plane of a router determine if byte counts for each source group entry exceed a threshold value, with messages sent from the forwarding plane to the control plane only for entries exceeding the threshold, initiating a switchover to a shortest path distribution tree, reducing the number of inter-process messages and improving scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional multicast distribution tree switchover methods are used in a multi-process environment, then the switchover from shared distribution tree to shortest path distribution tree can be performed, but the latency is high and the messaging overhead between control plane and forwarding plane increases significantly with large numbers of source group entries
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the shortest path distribution tree information in the forwarding plane database alongside the shared distribution tree information. When a switchover is needed, the forwarding plane can immediately use the pre-computed shortest path information without waiting for control plane calculations, thereby reducing switchover latency and minimizing messaging overhead between control and forwarding planes.
2Measurement precision
If the control plane sends messages to the forwarding plane for each source group entry to determine byte counts, then accurate traffic monitoring is achieved, but the number of messages increases linearly with the number of source group entries, reducing scalability
Solution Approach 1:
The patent applies self-service by enabling the forwarding plane to autonomously monitor byte counts for each source group entry using local counters and compare them against threshold values stored in the forwarding plane database. This eliminates the need for the control plane to send individual messages for each source group entry, reducing messaging overhead from linear to constant complexity while maintaining accurate traffic monitoring through the forwarding plane's self-managed counter mechanism.
3Reliability
If the system waits for control plane processing to determine switchover conditions, then centralized control is maintained, but the switchover time increases due to control plane processing delays
Solution Approach 1:
The patent applies segmentation by dividing the switchover decision-making process into two independent segments: (1) the forwarding plane segment that autonomously monitors byte counts and detects threshold violations using local counters, and (2) the control plane segment that receives notifications and updates routing tables. This segmentation allows the forwarding plane to perform real-time monitoring and immediate detection without waiting for control plane processing, while the control plane maintains centralized authority for actual routing table updates, thereby achieving both centralized control and fast switchover speed.
Data Source
AI summary
Described are a method and a device for efficiently switching multicast data flows from a shared distribution tree to a shortest path distribution tree. The method achieves an efficient and scalable tree switch that reduces the latency of multicast data transmitted from the source to receivers. A determination is made for each source group (S,G) entry in a portion of a forwarding plane database of a router as to whether a byte count for that entry exceeds a threshold value. A message sent from the forwarding plane to the router control plane indicates the (S,G) entries determined to have byte counts exceeding the respective threshold values. For each message entry, the respective shared distribution tree is switched to a shortest path distribution tree. The method achieves a substantial reduction in the number of inter-process messages exchanged between the control plane and the forwarding plane compared to conventional tree switchover techniques.