TCP Fast Open Cookie Bypass for Network Processor Cache Misses
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Solution Overview
Problem
Network processors face performance issues due to cache misses during TCP classification, particularly in scenarios where TCP connections follow an on/off pattern, leading to repeated classification processes and increased latency.
Innovation Solution
Implementing a system that generates a key from TCP metadata for packet classification, utilizing a packet cache to store recent network policy identifiers and leveraging TFO cookies to bypass classification when a valid rule ID is found, thus reducing the need for repeated classification processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a cache mechanism is used to accelerate classification, then classification speed is improved, but cache misses occur when TCP connections follow an on/off pattern, leading to repeated classification processes
Solution Approach 1:
The system performs preliminary classification during the initial TCP connection phase and stores the result in a TFO cookie. When the connection resumes after an on/off pattern, the pre-stored cookie allows immediate cache population without requiring full re-classification, thus maintaining high cache hit rates while preserving classification speed
Solution Approach 2:
The invention creates a simplified copy of classification information in the form of a TFO cookie that contains essential policy identifiers. This copy allows the system to reconstruct the full classification state without performing the expensive original classification process again, effectively bridging cache misses caused by TCP on/off patterns
2Productivity
If TCP fast open with cookies is used to bypass classification, then throughput is improved, but the system complexity increases due to additional cookie management
Solution Approach 1:
The TFO cookie mechanism serves multiple functions: it acts as a cache validation token, a classification result storage medium, and a connection state identifier. By making this single mechanism multi-functional, the system achieves throughput improvement without proportionally increasing complexity, as the same structure handles multiple classification-related tasks
Solution Approach 2:
The TFO cookie acts as an intermediary between the TCP connection state and the classification cache. Rather than directly managing complex classification state restoration, the system uses the simple cookie as a mediator that triggers appropriate cache behavior, reducing the overall system complexity while maintaining high throughput
Data Source
AI summary
A packet parser generates a key from TCP metadata of a data packet for a specific session. A packet cache stores recent network policy identifiers associated with a plurality of network sessions, wherein the key is used as an index to search the packet cache. The packet cache responsive to a cache miss, checks a TFO cookie field for a rule ID stored by the client during a previous session as generated by the network processor. If there is no rule ID, a classification pipeline is activated. On the other hand, responsive to a cache hit, or responsive to identifying a rule ID for the session from the TFO cookie, the classification pipeline is bypassed for the data packets of the specific session.