Dual-Slot MAC Address Table for Ethernet Switch Memory Optimization
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Solution Overview
Problem
Ethernet switches face limitations in efficiently utilizing limited memory for packet storage and lookup due to the small capacity of their address tables, which affects switching efficiency and forwarding control.
Innovation Solution
A dual-slot address table method using a hash function to map MAC addresses to designated and companion slots, with mechanisms for learning and inquiry, including dynamic and static learning, and the use of content-addressable memory (CAM) to optimize memory usage and reduce hardware requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a conventional dual-slot address table is used to store MAC addresses, then the address table can record MAC address information, but the memory space is insufficient to store more MAC addresses due to the fixed slot structure
Solution Approach 1:
The patent implements dynamic slot allocation where slots can be allocated or released based on whether they contain static or non-static MAC addresses. Non-static entries can be evicted to free slots for new entries, while static entries occupy dedicated slots. This dynamic management allows the address table to adapt to changing network conditions and maximize the number of stored MAC addresses within limited memory space.
Solution Approach 2:
The patent changes the state parameter of MAC address entries by introducing static and non-static flags. This parameter change enables the system to differentiate between entries that should be retained permanently (static) and those that can be replaced (non-static), thereby optimizing memory utilization and increasing the effective capacity of the address table.
2Productivity
If more MAC addresses are stored in the address table, then switching efficiency is improved, but hardware resources increase
Solution Approach 1:
The patent segments the address table into multiple slots with different characteristics (static and non-static). This segmentation allows efficient organization of MAC addresses by their retention requirements, enabling faster lookup operations while using compact memory structures. The segmented approach avoids the need for larger, more complex memory structures that would be required to store the same number of entries in a unified table.
Solution Approach 2:
The patent adds a temporal dimension to the address table by introducing age counters and static/non-static flags. This dimensional change transforms the simple key-value storage into a multi-dimensional structure that tracks entry age, stability, and replaceability. This additional dimensionality enables more intelligent memory management and improves switching efficiency without proportionally increasing hardware resources.
3Device complexity
If the address table uses fixed slot allocation, then the structure is simple, but memory efficiency is low due to inability to release occupied slots
Solution Approach 1:
The patent transforms the fixed slot allocation into a dynamic structure where slots can be allocated, released, and reallocated based on the nature of stored entries. Non-static entries can be evicted when their age counter expires or when memory pressure occurs, freeing slots for new entries. This dynamic behavior maintains structural simplicity while dramatically improving memory efficiency and the number of storable MAC addresses.
Data Source
AI summary
A method for managing medium access control (MAC) address and related apparatus are provided, including an MAC address learning method and an MAC addresses inquiring method. The learning method includes the steps of: mapping an MAC address to a designated slot and a companion slot in an address table; if said designated slot being empty, learning said MAC address into said designated slot; and if said designated slot being non-empty, said companion slot being empty and the content of said designated slot being non-static, moving the content of said designated slot to said companion slot and modifying a bit of the higher part of said MAC address in said companion slot and learning said MAC address into said designated slot.