Extended L3 Lookup Tables for Routing Table Capacity
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Solution Overview
Problem
Information handling systems face limitations in the size of their lookup tables, restricting the number of entries and possible forwarding destinations due to finite memory allocation, necessitating a method to extend these tables for enhanced routing capabilities.
Innovation Solution
The implementation of an information handling system with a plurality of forwarding processors and switching devices, where the switching devices perform extended lookups in their host and route tables based on fabric headers, effectively doubling the size of the routing tables by adding logical extensions to the forwarding processor's lookup tables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the memory allocated for routing tables is increased, then the number of entries and forwarding destinations can be increased, but the device complexity and cost increase
Solution Approach 1:
The routing table is segmented into two parts: a first routing table stored in forwarding processor memory and a second routing table stored in switching device memory. This segmentation allows the routing functionality to be distributed across multiple components, effectively increasing the total number of routing entries without requiring a single large memory allocation in one device, thereby reducing the complexity associated with managing large contiguous memory blocks.
Solution Approach 2:
The patent implements a nested lookup mechanism where the forwarding processor first performs a lookup in its local routing table, and if no match is found, the packet is forwarded to the switching device which performs a lookup in its routing table. This nested structure allows the system to effectively combine the capacity of multiple smaller routing tables into a larger logical routing table, increasing the number of supported routing entries without requiring each individual device to have large memory capacity.
2Quantity of substance
If the size of the routing table is increased, then more forwarding destinations are supported, but the lookup time and processing delay increase
Solution Approach 1:
The routing lookup process is segmented into two stages: first, the forwarding processor performs a quick lookup in its local routing table which contains frequently accessed or most common routing entries; second, only if no match is found does the packet get forwarded to the switching device for a lookup in its routing table. This segmentation ensures that the majority of lookups are completed quickly in the first stage, minimizing average lookup time while still providing access to a large total routing table capacity through the combined system.
Solution Approach 2:
The forwarding processor is pre-configured with a local routing table containing the most commonly accessed routing entries, allowing it to handle the majority of routing decisions without needing to query the switching device. This preliminary action of pre-loading frequently used routing information into the forwarding processor's memory reduces the need for time-consuming inter-device communication and lookups, thereby minimizing routing delay while maintaining support for a large number of forwarding destinations through the combined routing tables.
Data Source
AI summary
An information handling system is provided. The information handling system includes a plurality of forwarding processors, the plurality of forwarding processors each including a memory having a forwarding host table and a forwarding route table. The information handling system also includes at least one switching device coupled to the plurality of forwarding processors, the at least one switching device including a memory having a destination module and port table, a switching device host table and a switching device route table, wherein the at least one switching device is configured to perform an extended lookup in at least one of the switching device host table and switching device route table based on values included in a fabric header of information routed to the switching device to determine a destination of the information. A method for extending lookup tables is also provided that adds lookup tables in a switching device.