EVPN Designated Forwarder Election via Policy Negotiation
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Solution Overview
Problem
In EVPN multi-homing networks, the existing method of electing a designated forwarder (DF) can lead to erroneous results due to each PE using its locally configured election policy, resulting in multiple identical packets being sent to a CE, which causes inefficiencies and errors.
Innovation Solution
A method and device for electing a designated forwarder that allows PEs to determine a target election policy by negotiating and comparing election policies, ensuring all PEs elect the same DF, thereby preventing erroneous election results and ensuring efficient packet delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If each PE uses its locally configured election policy to elect the DF, then the election process is simple and decentralized, but multiple PEs may be elected as DF resulting in erroneous election results
Solution Approach 1:
The patent implements a feedback mechanism where PEs exchange election policy information through BGP messages. Each PE advertises its supported election policies and priorities to other PEs in the multi-homing group. Based on this feedback information, PEs can determine a common target election policy that all will use, ensuring consistent DF election results while maintaining the decentralized nature of the process.
Solution Approach 2:
The patent changes the election policy parameter from being locally configured and static to being dynamically determined through negotiation. PEs exchange their supported election policies and priorities, then select a target election policy based on predefined rules (such as selecting the policy with the highest priority that is supported by all PEs). This parameter change ensures all PEs use the same election policy while maintaining operational simplicity.
2Reliability
If a target election policy is determined through negotiation and comparison, then consistent DF election results are achieved across all PEs, but the election process becomes more complex
Solution Approach 1:
The patent applies preliminary action by having PEs exchange their supported election policies and priorities before the actual DF election takes place. This pre-negotiation phase allows all PEs to determine the target election policy in advance, ensuring consistency during the election. The complexity is front-loaded in the policy exchange phase, but the actual election process remains simple and reliable.
Solution Approach 2:
The patent uses BGP messages as an intermediary mechanism to facilitate policy exchange between PEs. Instead of PEs directly negotiating through complex interactions, they advertise their supported policies through standardized BGP attributes. This intermediary approach simplifies the negotiation process while ensuring all PEs receive consistent information about the target election policy.
Data Source
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AI summary
A method and a device for electing a designated forwarder are provided. According to the method, NLRI sent by a second PE of the PEs is received, and a first election policy set supported by the second PE, and a first priority corresponding to each election policy in the first election policy set is parsed out. A target election policy is determined by using a second election policy set supported by a first PE, a second priority corresponding to each election policy in the second election policy set, the first election policy set supported by the second PE and the first priority corresponding to each election policy in the first election policy set. A DF is elected from the first PE and the second PE by using the target election policy.