Router Redundancy via Dynamic Priority Adjustment
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Solution Overview
Problem
Existing router selection mechanisms for VRRP and multicast traffic in LAN segments are inefficient due to static criteria for designated forwarder (DF) and master router elections, which do not account for actual routing table contents, leading to potential multicast packet drops and divergent unicast and multicast forwarding paths.
Innovation Solution
Implementing intelligent DF and master router selection modules that dynamically adjust priority values based on the presence of routes in multicast and unicast routing tables, ensuring the most capable router is elected as both the DF and VRRP/VRRP-E master, thereby synchronizing election processes and optimizing forwarding paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If static criteria (preconfigured DF priority value and interface IP address) are used for DF election, then the election process is simple, but the elected DF may not have routes to multicast sources in its routing tables, causing multicast packet drops
Solution Approach 1:
The patent implements dynamic DF election by allowing routers to modify their DF priority values based on whether they have routes to multicast sources in their routing tables. Routers with routes can increase their priority, ensuring that the elected DF has the necessary routing information, thus resolving the contradiction between simple election process and reliable multicast forwarding
Solution Approach 2:
The patent performs preliminary route checking before the DF election takes place. Each router checks its routing tables for routes to multicast sources and adjusts its priority accordingly before the election occurs, ensuring that the election is based on actual forwarding capability rather than static configuration
2Adaptability or versatility
If separate mechanisms are used for VRRP master election and DF election, then each election can be optimized for its specific protocol, but the elected VRRP master and DF may be different routers, causing divergent unicast and multicast forwarding paths
Solution Approach 1:
The patent merges the VRRP master election and DF election processes by allowing the same priority modification mechanism to influence both elections. Routers modify their priorities based on route presence, and this modified priority is used in both VRRP and multicast DF elections, ensuring that the same router is elected for both roles and maintaining consistent forwarding paths
Solution Approach 2:
The patent uses parameter changes (priority values) as a common interface between VRRP and DF elections. By modifying the priority parameter based on routing table contents and using this same parameter in both election mechanisms, the patent ensures coordinated selection of master router and DF, eliminating path divergence
Data Source
AI summary
Techniques for intelligent designated forwarder (DF) and master router selection (for router redundancy) are provided. In one embodiment, a network router that is part of a set of network routers connected to a common LAN segment can retrieve a priority value adapted for use by the network router in electing a DF for multicast traffic. The network router can further check for the presence or absence of one or more routes to one or more multicast sources in a routing table of the network router. The network router can then modify the priority value based on the presence or the absence of the one or more routes and can transmit a multicast routing protocol control packet including the modified first priority value to one or more other network routers in the set of network routers.