SDN Switch Flow Table Entries Generate Control Packets
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Solution Overview
Problem
Conventional software-defined networking (SDN) systems face issues with overhead and complexity due to the need for dedicated state tables in forwarding elements, which require additional memory and management, leading to increased costs and error proneness.
Innovation Solution
Implementing an SDN capable forwarding switch with a packet pipeline that includes flow table entries (FTEs) configured to create and send control packets to the control engine, eliminating the need for a dedicated state table by using in-switch generated messages to update forwarding rules, thereby mimicking stateful forwarding behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dedicated state tables are used in forwarding elements to maintain stateful forwarding, then stateful forwarding capabilities are achieved, but hardware complexity and implementation costs increase
Solution Approach 1:
The patent extracts the state table functionality from the forwarding element hardware and relocates it to the SDN controller. Flow table entries now contain only forwarding rules without embedded state storage, separating the state management function from the forwarding path and eliminating dedicated state table hardware in switches.
Solution Approach 2:
The patent makes the SDN controller universal by having it perform both control plane functions and state table management. The controller becomes a multi-functional entity that handles flow rule distribution, state maintenance, and forwarding decisions, replacing the need for specialized state table hardware in each forwarding element.
2Reliability
If dedicated state tables are implemented in forwarding elements, then state tracking is improved, but additional memory and management overhead increase
Solution Approach 1:
The state tracking functionality is extracted from local forwarding element memory and consolidated in the SDN controller's memory resources. This centralizes state information storage, eliminating redundant memory requirements at each switch while maintaining comprehensive state tracking capabilities through controller-based management.
3Device complexity
If control is centralized in SDN controllers, then forwarding elements can be simplified, but communication overhead between switches and controllers increases
Solution Approach 1:
The patent applies preliminary action by having the SDN controller pre-compute and distribute complete flow table entries with all necessary forwarding rules and state information to forwarding elements before traffic arrives. This allows switches to operate autonomously based on pre-installed rules, minimizing real-time communication overhead with the controller.
Data Source
AI summary
A software-defined networking (“SDN”) capable forwarding switch includes ports for receiving and/or outputting data packets and a packet pipeline including a forwarding table. The forwarding table is configured to contain a number of flow table entries (“FTEs”), that determine the forwarding switch's configuration and control behavior. The switch further includes a control engine configured to manipulate the forwarding switch's forwarding tables by adding, updating, and/or removing FTEs in the forwarding tables. An FTE of a forwarding table is configured to contain a specific action part that includes an action instruction to create a control packet and to send it to the control engine. The control packet includes embedded control instructions that cause the control engine to change the forwarding switch's configuration and/or control behavior.