Spoke-to-Spoke Multicast via Enhanced PIM in DMVPN
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Solution Overview
Problem
Current Dynamic Multipoint Virtual Private Network (DMVPN) frameworks are limited in their ability to support multicast traffic, particularly in non-broadcast multi-access (NBMA) environments, where the hub router bears a significant replication load when the multicast source is located at a spoke site, and do not facilitate spoke-to-spoke multicasting efficiently.
Innovation Solution
The implementation of enhanced Protocol Independent Multicast (PIM) messaging, including a new receiver-list attribute, allows spoke routers to dynamically determine interested remote spokes and construct multicast routing entries independently of the hub router, enabling spoke-to-spoke multicasting without requiring IGP routing protocol adjacency or NHRP, and allowing for cooperative load sharing between hub and spoke routers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multicast traffic is routed through the hub router in a DMVPN framework, then connectivity is maintained, but the hub router experiences significant replication load
Solution Approach 1:
The patent segments the multicast routing function by allowing spoke routers to independently construct multicast routing entries and establish spoke-to-spoke tunnels. This divides the replication load from the hub router to the spoke routers, maintaining connectivity while reducing hub burden.
Solution Approach 2:
The patent extracts the multicast routing decision-making process from the hub router and places it at the spoke routers. Spoke routers now independently determine multicast group membership and construct routing entries, removing the replication burden from the hub while preserving multicast functionality.
2Productivity
If spoke-to-spoke multicasting is enabled, then network efficiency improves, but protocol complexity increases
Solution Approach 1:
The patent makes the PIM join message multi-functional by enabling it to carry both traditional multicast join information and spoke-to-spoke tunnel establishment information. This universal message structure enables efficient spoke-to-spoke multicasting without requiring separate complex protocols.
Solution Approach 2:
The patent merges the multicast routing function with the existing PIM protocol framework. By integrating spoke-to-spoke tunnel construction into the standard PIM join message flow, the patent achieves network efficiency without adding significant protocol complexity.
3Measurement precision
If the hub router maintains full control of multicast routing, then routing accuracy is ensured, but network scalability is limited
Solution Approach 1:
The patent applies local quality by enabling each spoke router to independently construct multicast routing entries based on local PIM message analysis. This distributed approach improves network scalability while maintaining routing accuracy through localized decision-making at each router.
Solution Approach 2:
The patent implements preliminary action by having spoke routers pre-construct multicast routing entries and establish tunnels before actual multicast traffic flows. This preparatory routing setup enables scalable network growth while ensuring accurate routing from the outset.
Data Source
AI summary
A method is provided in one example implementation and includes sending a PIM join message to the second spoke router by the hub router. The second spoke router dynamically determines each interested remote spoke router by parsing a hub-sent PIM message and accordingly constructs the multicast routing entry such that the first and second spoke routers establish multicast communication independent of a hub router. In more specific embodiments, the PIM join/prune messaging includes a list of each downstream spoke router that sent a PIM join/prune, in a new attribute. The PIM join/prune message is sent by the hub router towards a multicast source. A new receiver-list attribute is created that the hub router populates with a non-broadcast multi-access (NBMA) address for each interested spoke router.