Hybrid CAM RAM Packet Classification Memory Utilization
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Solution Overview
Problem
Media gateways face inefficiencies in memory utilization for packet classification due to the high cost and physical size of content addressable memory (CAM) required for session identification, necessitating improved methods for storing and searching session information.
Innovation Solution
Storing session identifiers in a memory as a combination of local and remote network addresses and port numbers, allowing for efficient classification of incoming and outgoing packets using destination and source addresses and port numbers, thereby optimizing the use of CAM and reducing the number of bits required for each search field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If content addressable memory (CAM) is used for session identification in packet classification, then packet processing speed is improved, but manufacturing cost and physical size increase
Solution Approach 1:
The patent segments the session identification process into two parts: a smaller CAM table storing only local network addresses and port numbers, and a larger RAM table storing complete session information including remote addresses. This segmentation allows the system to maintain fast packet processing for common local lookups while avoiding the high cost of a single large CAM table.
Solution Approach 2:
The patent introduces an intermediary structure (the hybrid table in RAM) that mediates between the small CAM and the full session information. When a packet arrives, the system first performs a quick CAM lookup on local address and port, then uses the result to retrieve complete session information from RAM, thus avoiding the need for a large expensive CAM while maintaining processing speed.
2Productivity
If content addressable memory (CAM) is used for session identification, then packet classification efficiency is improved, but physical space requirements increase
Solution Approach 1:
The patent divides the memory requirements into two segments: a compact CAM structure occupying minimal physical space for storing local address and port combinations, and a larger RAM structure for complete session information. This physical space segmentation enables efficient packet classification while constraining the physical footprint of critical lookup structures.
3Device complexity
If traditional session table storage methods are used, then implementation simplicity is maintained, but memory utilization efficiency decreases
Solution Approach 1:
The patent applies local quality by storing different types of information in different memory locations with different access characteristics. The CAM table stores frequently accessed local address and port data with fast access properties, while RAM stores complete session information. This local optimization of data placement improves overall memory utilization efficiency while maintaining implementation feasibility.
Data Source
AI summary
Methods and systems for classifying incoming and/or outgoing packets to sessions in a media gateway store session identifiers for active sessions in a media gateway in a memory. Each session identifier is a combination of a local network address, a local port number, a remote network address, and a remote port number for the session. Alternatively, each session identifier is a combination of a local network address and a local port number. An incoming and/or outgoing packet is classified to one of the active sessions by using network address and port number information from the packet to perform a lookup for a corresponding session identifier in the memory.