Layer 3 Host Table Entry Replacement Using Packet Volume Thresholds
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Solution Overview
Problem
Conventional layer 3 packet forwarding devices face challenges with limited space in hardware forwarding tables, leading to excessive replacement of entries and increased lookup times due to the least recently used (LRU) algorithm, which does not account for packet volume or destination usage.
Innovation Solution
Implementing a method to control the updating of the layer 3 host table based on packet forwarding miss counts, where remote destination entries are replaced only when their miss counts exceed a threshold, and considering the age of entries to optimize table management and reduce thrashing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LRU algorithm is used to replace host table entries, then newer entries are added to the host table, but excessive replacement occurs leading to processor intensive operations
Solution Approach 1:
The patent changes the replacement parameter from simple recency (LRU) to a composite parameter considering both recency and packet volume. This is implemented by maintaining a packet volume counter for each destination and using it as a threshold for replacement decisions, thereby reducing excessive replacements while maintaining adaptability
Solution Approach 2:
The patent introduces feedback mechanisms by counting packets per destination and using this information to control replacement decisions. The system monitors packet volumes and adjusts replacement behavior based on this feedback, preventing premature removal of high-volume destinations from the host table
2Adaptability or versatility
If LRU algorithm replaces entries based on individual packets, then new entries are quickly added, but high-volume entries are incorrectly replaced
Solution Approach 1:
The patent modifies the replacement criterion by introducing packet volume as an additional parameter alongside recency. The system now considers both how recently an entry was used and how many packets were directed to it, preventing the replacement of high-volume entries that were simply not accessed recently
Solution Approach 2:
The patent implements feedback by tracking packet volumes for each destination and using this information to guide replacement decisions. The system learns from past packet distributions and adjusts its replacement behavior accordingly, maintaining high-volume entries in the host table
3Speed
If hardware forwarding tables are used to increase lookup speed, then packet forwarding efficiency is improved, but table space becomes limited
Solution Approach 1:
The patent changes the parameters used for table population from simple recency-based criteria to a more sophisticated model incorporating packet volume thresholds. This allows more intelligent utilization of limited hardware table space by prioritizing entries with higher packet volumes
Solution Approach 2:
The patent applies partial action by selectively adding only those destinations to the host table that meet the packet volume threshold criterion. Rather than populating the table with all possible entries, it focuses resources on the most relevant destinations, effectively managing limited table capacity
Data Source
AI summary
An indication of a host route to be added to a forwarding database table as an entry is received. The host route is added to a first hardware table or a second hardware table if a space is available in the second hardware table or in a first storage area of the first hardware table. The first hardware table has both a first storage area and a second storage area. If a space is not available in the second hardware table or the first storage area of the first hardware table, the first storage area of the first hardware table is automatically expanded to include unused space in the second storage area of the first hardware table. The host route is then added to a space in the expanded first storage area of the first hardware table.