Non-Designated Router Multicast Buffering for Fast Failover

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Solution Overview

Problem

In Protocol Independent Multicast-Sparse Mode (PIM-SM) networks, the failure of a designated router leads to significant delays in recovering multicast traffic, causing glitches in audio/video streams due to the time taken to detect failure and switch to a new designated router.

Innovation Solution

Configuring non-designated routers to receive and potentially forward multicast streams, allowing them to quickly take over as designated routers upon failure detection, using mechanisms like hello messages and priority exchange to reduce recovery time, and employing protocols like PIM-SM and IGMP for efficient routing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If only the designated router receives multicast traffic, then the network follows standard PIM-SM protocol behavior, but recovery time from designated router failure is prolonged (several seconds)

Engineering Contradiction:

Improvemulticast traffic continuityVSAvoidrecovery time from designated router failure

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Non-designated routers perform preliminary actions by receiving and buffering multicast traffic before they are needed for failover. This includes subscribing to multicast groups, receiving traffic from upstream routers, and maintaining it in memory ready for immediate forwarding upon designated router failure, thus eliminating the need to re-establish traffic flow after failure detection

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically changes the operational state of non-designated routers from passive to active multicast receivers based on failure detection. When the designated router fails, non-designated routers transition from discarding multicast traffic to actively receiving and forwarding it, changing their reception parameter from false to true

Inventive Principle:

Principle #35Parameter changes

2Loss of time

If non-designated routers receive and buffer multicast traffic, then recovery time is reduced to milliseconds, but network complexity and resource consumption increase

Engineering Contradiction:

Improverecovery time from designated router failureVSAvoidrouter configuration and operation

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

Non-designated routers automatically manage their own multicast reception state without requiring manual configuration or complex coordination protocols. Upon detecting designated router failure through standard hello message mechanisms, they self-activate to receive and forward multicast traffic, and automatically deactivate when a new designated router is established, simplifying the overall system operation

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

Routers in the network are designed to perform multiple functions: they can operate as designated routers receiving and forwarding multicast traffic, or as non-designated routers that also have the capability to receive and buffer multicast traffic for potential failover. This multi-functionality allows any router to potentially take over the designated router role, reducing single points of failure

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8576702B2Receiving multicast traffic at non-designated routers

Publication Date: 2013.11.05 WSOU INVESTMENTS LLC

AI summary

A multicast stream is received. At a non-designated router, a multicast stream is received with respect to which the non-designated router is not a designated router responsible for sending the multicast stream to a host. The received multicast stream is discarded.