IP Router Link Failure Recovery via Detour Branching
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Solution Overview
Problem
Existing IP networks face challenges in quickly recovering from link failures without creating routing loops, which can lead to packet drops and reduced service levels, especially in densely connected networks where management of tunneling interfaces and addresses becomes cumbersome.
Innovation Solution
The method involves defining default and detour branchings for each node in the network, allowing per-node decision-making to switch from a default path to a detour path in case of link failure, without requiring additional interface addresses or tunneling, and dropping packets if they are on a detour path when a second failure occurs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional routing protocols (OSPF, IS-IS) are used for link failure recovery, then routing tables are re-computed across the network, but this process takes significant time due to link transmission delays and re-computation time, causing packet drops and reduced service levels
Solution Approach 1:
The patent pre-computes alternative routes (detour branchings) for each node in the network before failures occur. When a link failure is detected, routers can immediately switch to pre-computed alternative routes without waiting for network-wide routing table re-computation, thus reducing recovery time and preventing packet drops
2Speed
If IP Fast Reroute (IPFRR) with Not-via Addresses is used for fast local rerouting, then packet forwarding can be quickly switched to alternative paths, but this requires tunneling and provision of two IP addresses per interface, making administration and management cumbersome in densely connected networks
Solution Approach 1:
The patent segments the network routing into default branchings and detour branchings for each node. Each router maintains separate routing information for normal and alternative paths, allowing fast switching without requiring tunneling interfaces or additional IP addresses per interface, thus reducing administrative complexity
3Reliability
If Failure Insensitive Routing (FIR) is used to reduce loop creation risk, then routing tables are provided on a per line card basis with different egress interfaces for different ingress interfaces, but this can still create routing loops when multiple link failures occur
Solution Approach 1:
The patent pre-computes detour branchings that are guaranteed to be loop-free by construction, using algorithms that ensure acyclic paths. When failures occur, routers switch to these pre-validated detour paths, eliminating the need for complex per-line-card routing table configurations and preventing loops even with multiple failures
Data Source
AI summary
A method of routing packets across a packet switched network domain, comprising a multiplicity of nodes. Each node comprises an ingress interface and an egress interface. For each destination node a default and a detour branching are defined, each specifying a route to the destination node. For each two-edge connected node the default and detour branchings do not share a common ingress interface. Each node operates as an intermediate node receiving a packet at an ingress interface, identifying an egress interface based upon the ingress interface upon which the packet is received and the packet destination, forwarding the packet via that egress interface if the connected link is available and, if the connected link is not available, forwarding the packet via an alternative egress interface associated with said detour branching if the packet was received at an ingress interface associated with said default branching or dropping the packet if the packet was received at an ingress interface associated with said detour branching.