Hierarchical SDN Controller Architecture for Scalability
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Solution Overview
Problem
The scalability and flexibility of software-defined network (SDN) environments are limited by the number of switches that a controller can manage, leading to degraded network performance and increased errors due to complex network environments.
Innovation Solution
A divided hierarchical network system is implemented, where the network is divided into smaller networks, with an orchestrator generating edge controllers to manage edge divided networks, allowing each controller to focus on its directly connected lower network, and utilizing a converter unit to query upper-level forwarding information when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single controller manages all switches in an SDN network, then centralized control is achieved, but the number of manageable switches is limited and scalability is degraded
Solution Approach 1:
The network is divided into multiple edge divided networks, each managed by a separate edge controller. This segmentation allows the system to scale beyond the management capacity of a single controller while maintaining centralized control through hierarchical organization. Each edge controller manages a specific subset of switches, reducing the complexity burden on individual controllers.
Solution Approach 2:
The system transitions from a flat single-level controller architecture to a hierarchical multi-level architecture. Edge controllers operate at the network edge level while an orchestrator operates at the system level, adding a dimensional layer to the control structure. This hierarchical dimension enables scalable management of large numbers of switches.
2Adaptability or versatility
If the network is divided into smaller networks hierarchically, then scalability is improved, but forwarding information generation becomes more complex requiring coordination between multiple controllers
Solution Approach 1:
Forwarding information generation is segmented between edge controllers and the orchestrator. Edge controllers generate forwarding information for their local edge divided networks, while the orchestrator coordinates cross-network forwarding. This segmentation reduces the complexity burden on each individual controller.
Solution Approach 2:
The orchestrator acts as an intermediary between edge controllers, facilitating coordinated forwarding information generation across multiple edge divided networks. When forwarding requires coordination between networks, the orchestrator mediates the information exchange and path calculation, simplifying the process for individual edge controllers.
3Reliability
If controllers manage the entire network topology, then comprehensive control is achieved, but the load on each controller increases significantly
Solution Approach 1:
The network topology management responsibility is segmented between edge controllers and the orchestrator. Each edge controller manages only its local edge divided network topology, while the orchestrator maintains the global topology view. This segmentation significantly reduces the processing load and memory requirements for each individual controller.
Solution Approach 2:
Edge controllers autonomously manage their own local network topology and forwarding decisions without requiring comprehensive knowledge of the entire network. This self-service approach reduces inter-controller communication overhead and processing load while maintaining reliable local control.
4Adaptability or versatility
If the network environment becomes more complex, then more functionality is required, but errors due to network complexity increase
Solution Approach 1:
The network is segmented into multiple isolated edge divided networks, each with its own edge controller. This segmentation limits the propagation of errors to local segments rather than affecting the entire network, improving reliability while maintaining comprehensive functionality through the orchestrator's coordination capability.
Data Source
AI summary
A divided hierarchical network system based on software-defined networks, the divided hierarchical network system including: an edge controller configured to: generate forwarding information in response to a flow forwarding inquiry from a lower level and respond to the request with the forwarding information; generate mapping information such that each of a plurality of edge ports of each of a plurality of switches that form the lower level corresponds to each of a plurality of virtual ports of one virtual switch; if it is not possible to generate forwarding information in response to a request received from a lower level for forwarding a flow that comprises edge ports, query forwarding information to an upper level regarding a flow in which the edge port is converted into a corresponding virtual port based on the mapping information.