Exact Match and Longest Prefix Match Table Lookup for Network Routing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current network elements face inefficiencies in routing data due to the high cost and power requirements of implementing longest prefix match tables, which are necessary for determining the transmission interface and next hop for packets based on destination addresses.
Innovation Solution
A method and apparatus that utilize both an exact match table and a longest prefix match table to perform concurrent lookups, generating keys from destination addresses to determine next hops, allowing for more efficient forwarding decisions by leveraging the strengths of both table types.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a longest prefix match table is used to store forwarding table entries, then the network element can determine transmission interface and next hop for packets, but the implementation becomes expensive in terms of chip area and power
Solution Approach 1:
The patent segments the forwarding table into two separate structures: an exact match table storing specific prefix-length entries and a longest prefix match table storing variable-length prefix entries. This segmentation allows the system to use the more efficient exact match table for specific routes while maintaining LPM capability for default routing, thereby reducing overall chip area requirements while preserving forwarding accuracy.
Solution Approach 2:
The patent extracts specific prefix-length entries from the conventional longest prefix match table and stores them separately in an exact match table. This extraction enables the system to handle commonly used specific routes through efficient exact matching, reducing the burden on the LPM table and minimizing the chip area needed for LPM implementation.
2Reliability
If a longest prefix match table is used to store forwarding table entries, then the network element can determine transmission interface and next hop for packets, but the power consumption increases
Solution Approach 1:
By segmenting the forwarding table into exact match and LPM components, the system can process specific routes through the lower-power exact match table, reducing the overall power consumption compared to using a full LPM table for all routing decisions.
Solution Approach 2:
Extracting specific prefix entries into a separate exact match table allows the system to bypass power-intensive LPM operations for commonly accessed routes, thereby reducing total power consumption while maintaining accurate forwarding decisions.
3Speed
If only an exact match table is used, then lookup speed is improved, but the ability to perform longest prefix match routing is lost
Solution Approach 1:
The patent merges the exact match table and LPM table into a unified forwarding system where both structures work together. The exact match table provides fast lookup for specific routes, while the LPM table maintains the ability to perform longest prefix match routing for default and variable-length routes, thus combining speed and versatility.
Solution Approach 2:
The forwarding system achieves multi-functionality by implementing both exact match and LPM capabilities within the same network element. This allows the system to adapt to different routing scenarios—using exact match for specific routes and LPM for default routing—thereby maintaining both lookup speed and routing flexibility.
Data Source
AI summary
A method and apparatus of a device that determines a match for a destination address using an exact match table and a longest prefix match table of a network element is described. In an exemplary embodiment, the network element receives a data packet that includes a destination address. The network element generates a key for the destination address, wherein the key represents more addresses than the destination address. The network element further performs an address lookup using the key in an exact match table. Furthermore, a match in the address lookup indicates a first transmitting interface of the network element. The network element additionally performs an address lookup using the destination address with a longest prefix match table, wherein a match in the address lookup indicates a second transmitting interface of the network element. In addition, the network element determines a resulting transmitting interface based on results from the exact match table address lookup and the longest prefix match address lookup. The network element forwards the data packet using the transmitting interface.