Virtual Gateway Multicast Forwarding via Designated Forwarder Selection
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Solution Overview
Problem
Existing technologies face challenges in efficiently forwarding bidirectional multicast traffic in virtual gateway devices, leading to significant traffic loss and flow duplication due to substantial convergence times during switch unavailability.
Innovation Solution
Elect one participating switch as a forwarding device (FS) and multiple switches as designated forwarders (DFs) within a virtual gateway device, allowing the FS to program forwarding entries in hardware and enabling quick convergence during unavailability events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional multicast forwarding is used in virtual gateway devices, then traffic can be forwarded, but significant traffic loss and flow duplication occur due to substantial convergence times during switch unavailability
Solution Approach 1:
The patent applies preliminary action by pre-configuring backup forwarding paths and pre-establishing virtual gateway device states before failover occurs. When a switch becomes unavailable, the backup device can immediately activate without waiting for convergence, thus eliminating traffic loss while maintaining forwarding reliability
Solution Approach 2:
The patent implements beforehand cushioning by creating redundant virtual gateway device instances that remain in standby mode with pre-synchronized state information. This cushioning mechanism ensures that when the primary switch fails, the backup device is already prepared to take over instantly, preventing both traffic loss and flow duplication
2Reliability
If multiple switches act as forwarding devices in a virtual gateway device, then high availability is improved, but flow duplication occurs
Solution Approach 1:
The patent uses an intermediary mechanism in the form of a designated forwarder role that mediates between multiple virtual gateway device instances. Only the designated forwarder actively forwards multicast traffic, while other instances remain in standby mode, thus achieving high availability without causing flow duplication. The intermediary role ensures single-point forwarding even with multiple potential devices
Solution Approach 2:
The patent applies local quality by assigning different functional states to different virtual gateway device instances based on their current operational role. The designated forwarder has active forwarding capability while standby instances have passive readiness, creating localized functional differentiation that prevents flow duplication while maintaining overall system availability
3Loss of time
If convergence time is reduced for fast failover, then traffic loss is minimized, but forwarding precision and traffic accuracy may be compromised
Solution Approach 1:
The patent applies preliminary action by pre-synchronizing the forwarding state information across all virtual gateway device instances before failover occurs. This pre-synchronization ensures that when the designated forwarder changes, the new forwarder already has the correct forwarding table and state information, enabling instant failover without sacrificing forwarding precision or causing traffic inaccuracies
Data Source
AI summary
A first network device in a network is provided. During operation, the first network device can elect the first network device as a designated forwarder (DF) of multicast traffic in a subnet for a Rendezvous Point (RP) of a multicast group. Here, the first network device can operate in conjunction with a second network device as a virtual gateway device of the subnet. The second network device can be elected as another DF for the RP. The first network device can determine whether the first network device is elected as a forwarding device based on a selection parameter. Upon determining that the first network device is elected as the forwarding device, the first network device can program, in the forwarding hardware, a forwarding entry for forwarding the multicast traffic. The first network device can then forward multicast traffic associated with the multicast group based on the forwarding entry.