EIGRP Non-Eligible Backup Paths for Forwarding Delay Reduction
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Solution Overview
Problem
In communications networks employing Enhanced Interior Gateway Routing Protocol (EIGRP), there is a delay in packet forwarding when a primary path becomes unavailable due to the lack of a feasible successor, leading to network convergence issues, as existing protocols do not utilize non-eligible distance vector protocol paths as backup paths effectively.
Innovation Solution
The method involves sending proactive distance vector protocol request messages to identify alternative, non-eligible loop-free paths from neighboring packet switching devices, which are then programmed as backup paths to ensure continuous packet forwarding until network convergence occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EIGRP protocol strictly enforces feasible successor eligibility criteria, then routing loop freedom is guaranteed, but backup path availability is reduced causing forwarding delays
Solution Approach 1:
The patent proactively identifies and installs non-eligible backup paths before primary path failure occurs. By performing preliminary path discovery and validation, the system prepares alternative routes in advance, eliminating the need to wait for failure detection and route recalculation, thus reducing forwarding delay while maintaining routing loop freedom through careful path selection criteria
Solution Approach 2:
The patent modifies the path selection parameters by relaxing the feasible successor eligibility criteria for backup path identification. Instead of strictly requiring reported distance less than feasible distance, the system accepts paths meeting less stringent conditions, expanding the pool of available backup paths while implementing additional safeguards to prevent routing loops
2Speed
If EIGRP uses only feasible successors as backup paths, then convergence speed is limited by protocol constraints, but network stability is maintained
Solution Approach 1:
The patent segments the backup path selection process into two independent stages: (1) traditional EIGRP feasible successor selection for immediate backup, and (2) proactive non-eligible path discovery for extended backup options. This segmentation allows the system to maintain protocol compliance while adding enhanced capabilities, improving convergence speed without completely redesigning the protocol architecture
Solution Approach 2:
The patent introduces an intermediary mechanism that sits between the primary path failure detection and the backup path activation. This intermediary proactively discovers and pre-validates alternative paths, acting as a buffer that accelerates the convergence process by having backup routes ready before they are needed, thus improving speed without adding significant protocol complexity
3Adaptability or versatility
If proactive path discovery is implemented, then backup path availability increases, but protocol message overhead increases
Solution Approach 1:
The patent implements partial proactive path discovery by selectively querying only certain neighbors for alternative paths rather than all neighbors. This partial action approach balances the need for backup path availability with the cost of message overhead, obtaining sufficient path information without generating excessive protocol traffic that would burden the network
Data Source
AI summary
In one embodiment, non-eligible distance vector protocol paths are used as backup paths. In one embodiment, the distance vector protocol is Enhanced Interior Gateway Protocol (EIGRP) and unless a path is a feasible successor for a destination, the path is not eligible as a backup path. Therefore, if there is no feasible successor, there is no eligible backup path. One embodiment avoids an initial delay in finding a replacement path for traffic by determining and installing a non-eligible backup path (e.g., a path that is not a feasible successor) in one or more forwarding tables. In this manner, the router can immediately forward packets over this non-eligible backup path until, for example, forwarding in the network can converge in light of the primary path being no longer available.