Router Forwarding Table Loop-Free Routing via BGP Augmentation
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Solution Overview
Problem
Capacity-limited forwarding tables in routers cannot support the full internet routing table, leading to routing loops and increased costs when additional TCAM is deployed, and manual filtering of BGP routes is inefficient and prone to human error.
Innovation Solution
Automatically identifying and augmenting BGP routes to be installed in the forwarding table with longer-prefix matches from another set, using a table-map to filter routes and ensure loop-free topology without the need for external TCAM, thereby maintaining cost advantages of merchant silicon network processing devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If additional TCAM is deployed to increase forwarding table capacity, then the router can support the full internet routing table, but the cost increases considerably and resources are consumed that could be used for other purposes
Solution Approach 1:
The patent segments the forwarding table capacity by implementing a hierarchical structure with a small TCAM storing only critical longer-prefix routes and a larger RAM-based structure storing the complete forwarding table. This segmentation allows the system to achieve full routing table support while minimizing expensive TCAM usage, directly resolving the contradiction between forwarding table capacity and system cost.
2Quantity of substance
If BGP routes are filtered between the BGP process and the FIB to prevent exceeding route capacity, then the forwarding table can be kept within limits, but routing loops occur
Solution Approach 1:
The patent implements a feedback mechanism where the system automatically monitors the forwarding table capacity and dynamically adjusts route installation decisions. When the table approaches capacity limits, the system selectively prioritizes longer-prefix routes (which are more specific and critical for loop prevention) while filtering less critical routes, thereby maintaining both capacity constraints and loop-free topology without manual intervention.
3Reliability
If manual filtering of BGP routes is performed to identify loop sources, then routing loops can be prevented, but the process is time-consuming, subject to human error, and difficult to implement permanently
Solution Approach 1:
The patent implements a self-service automated system that performs route filtering and loop prevention without manual intervention. The system automatically analyzes BGP routes, identifies potential loop sources, and configures appropriate filtering rules based on the hierarchical forwarding table structure. This automation eliminates human error, reduces configuration time, and provides permanent implementation, directly resolving the contradiction between reliability and time loss.
Data Source
AI summary
A router includes a plurality of ports interconnected to one or more Customer Edge (CE) nodes and one or more Provider Edge (PE) nodes; and memory storing a forwarding table of routes, wherein the routes in the forwarding table are installed automatically based on static or Interior Gateway Protocol (IGP)-learned default routes, connected routes, Border Gateway Protocol (BGP) routes learned from peers, and routes in an Internet routing table, and wherein a number of the routes installed in the forwarding table is less than a number of routes in the Internet routing table. The number of routes in the Internet routing table exceeds a capacity of the memory, and the routes installed in the forwarding table ensure a loop-free topology. The routes installed in the forwarding table can include all of the BGP routes learned from peers plus longer prefix matches from the routes in the Internet routing table.