Router Line Card Architecture for Packet Forwarding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Network routers face inefficiencies due to the limited memory capacity of merchant silicon-based line cards, which cannot store full forwarding tables, and the high cost of custom ASIC-based line cards with large memory capacity.
Innovation Solution
A router architecture that combines commodity silicon CPU-based line cards with partial forwarding tables and network processing unit-based line cards, where the CPU-based line cards store a full forwarding table and the NPU-based line cards store a subset of frequently used entries, allowing packets to be forwarded using either matching entries in the partial table or the full table.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If merchant silicon-based line cards are used, then cost is reduced, but memory capacity for storing forwarding tables is limited
Solution Approach 1:
The forwarding table storage function is segmented between two types of line cards: NPU-based line cards store a first forwarding table with frequently accessed entries, while CPU-based line cards store a second forwarding table with remaining entries. This segmentation allows merchant silicon NPU line cards to handle common routing efficiently without requiring full forwarding table capacity, thus reducing cost while maintaining sufficient memory capacity for high-speed forwarding.
2Quantity of substance
If custom ASIC-based line cards are used, then memory capacity for large forwarding tables is achieved, but cost increases
Solution Approach 1:
Instead of requiring full forwarding table capacity in every line card, the system implements partial forwarding tables in NPU-based line cards containing only the most frequently accessed entries. This partial action approach allows merchant silicon line cards to handle the majority of routing traffic without the full memory capacity of custom ASIC line cards, significantly reducing cost while maintaining adequate performance for common routing scenarios.
3Speed
If full forwarding table is stored in NPU-based line card, then packet forwarding speed is maximized, but device complexity and cost increase
Solution Approach 1:
The system applies local quality by placing different forwarding table entries in different locations based on their access frequency. The NPU-based line card contains locally optimized first forwarding table entries for frequently accessed routes, enabling fast packet forwarding for common traffic. Less frequently accessed entries are stored in CPU-based line cards, accepting slower processing only when necessary. This local optimization maximizes forwarding speed for the majority of traffic without the complexity and cost of full forwarding tables in all line cards.
Data Source
AI summary
A router may include a central processing unit-based line card storing a forwarding table that includes a first set of entries, a network processing unit-based line card storing a partial forwarding table that includes a second set of entries comprising a subset of the first set of entries, where the second set of entries comprises entries that are most utilized by a plurality of line cards of the router, and a route controller for updating the second set of entries to comprise the entries that are the most utilized. The network processing unit-based line card may forward a packet when an entry in the partial forwarding table matches the packet and may forward the packet to the central processing unit-based line card to forward the packet when there is no entry in the partial forwarding table of the network processing-unit based line card that matches the packet.