Virtual Flow Tables for SDN Packet Forwarding
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Solution Overview
Problem
The OpenFlow protocol's requirement for sequential flow tables in SDN systems leads to inefficiencies in packet forwarding, particularly in applications like L2 transparent bridging and L3 RPF filtering, due to duplication of match fields and increased storage and processing overhead, which limits scalability.
Innovation Solution
The implementation of virtual tables that map to flow tables, allowing shared matching fields and reducing duplication, thereby saving storage and processing resources while maintaining efficient packet processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flow tables are sequentially numbered and packets are processed through a flow table pipeline in OpenFlow switches, then packet forwarding can be implemented according to the OpenFlow protocol, but match fields must be stored multiple times in different flow tables leading to increased storage overhead and processing complexity
Solution Approach 1:
The patent implements a virtual table system where a single flow table can serve multiple virtual tables, allowing the same physical flow table to be shared across different virtual networking functions. This multi-functionality eliminates the need to duplicate match fields across multiple physical flow tables while maintaining OpenFlow protocol compliance through the virtualization layer.
Solution Approach 2:
The virtual table acts as an intermediary layer between the control plane and the physical flow tables. It provides a logical abstraction that allows multiple virtual tables to reference the same physical flow table entries without duplication, thereby reducing storage overhead while maintaining protocol compliance.
2Productivity
If match fields are configured a priori in each flow table by the SDN controller, then flow table lookup can be performed, but duplicate match fields consume additional storage space and increase synchronization complexity
Solution Approach 1:
The patent merges multiple virtual tables onto a single physical flow table, consolidating duplicate match fields into one shared resource. This reduces storage space requirements and eliminates the need to synchronize identical match field configurations across multiple flow tables, thereby reducing synchronization complexity while maintaining forwarding efficiency.
3Adaptability or versatility
If multiple flow tables are used for different networking functions, then network virtualization can be achieved, but the sequential processing pipeline increases processing overhead and reduces scalability
Solution Approach 1:
By allowing a single physical flow table to serve multiple virtual tables simultaneously, the system achieves network virtualization functionality without requiring separate physical flow tables for each virtual network function. This multi-functionality reduces the total number of flow table processing stages in the pipeline, thereby reducing processing overhead and improving scalability.
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
In one embodiment, a method is implemented in a network element coupled to the SDN system, which contains a set of network elements processing traffic flows and a SDN controller managing the set of network elements. The method includes creating a set of virtual tables for processing packets of traffic flows at the network element based on a set of flow tables of the network element, where the set of flow tables is ordered in a sequence. The method further includes mapping each of the set of virtual tables to a single flow table of the set of flow tables, where the mapping causes at least one flow table being mapped to a plurality of the set of virtual tables. The method also includes forwarding packets of traffic flows to the set of virtual tables for processing.