SDN Link Discovery via Switch Autonomy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In software-defined networking (SDN), the current link discovery methods result in a heavy load on the control channel and increased processing overheads due to the large number of packet_out requests sent by the controller to switches, especially in large networks with tens of thousands of switches and numerous ports, leading to inefficiencies in topology discovery.
Innovation Solution
The proposed method reduces packets sent from the control plane to the forwarding plane by instructing each forwarding plane device to send a topology discovery packet at each port and receiving messages that carry identifiers of connected devices, allowing the control plane to determine topology connections with reduced overhead, thereby minimizing the number of packets sent and processing requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the controller regularly sends packet_out requests to each switch port to discover topology, then the topology discovery completeness is improved, but the control plane processing overhead increases significantly
Solution Approach 1:
Instead of the controller actively sending packet_out requests to each switch port to discover topology, the invention inverts the approach by having switches autonomously generate and send LLDP packets to their neighbors, with the controller passively receiving the packet_in messages to build the topology map. This inversion dramatically reduces control plane overhead while maintaining complete topology discovery.
Solution Approach 2:
The invention enables switches to perform topology discovery autonomously without continuous controller intervention. Each switch self-generates LLDP packets, sends them to connected ports, and the controller simply collects the returned packet_in messages. This self-service mechanism eliminates the need for the controller to manage individual packet_out requests for each port.
2Measurement precision
If the controller sends packet_out requests to N switches with P ports each, then the topology coverage is improved, but the number of control channel packets increases to N×P per period
Solution Approach 1:
Switches autonomously generate and send LLDP packets on all their ports without controller intervention. Each switch independently manages its own topology advertisement, eliminating the need for the controller to send individual packet_out requests to each of the N×P port combinations, thus dramatically reducing control channel packet volume.
Solution Approach 2:
The topology discovery function is segmented and distributed to individual switches rather than being centralized in the controller. Each switch independently performs discovery on its own ports, dividing the overall discovery task into N independent sub-tasks executed by switches, reducing the control plane's packet management burden from N×P individual requests to a single global discovery cycle.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
This application provides a link discovery method and an apparatus. The method includes: sending, by a control plane device, a first message to a plurality of forwarding plane devices in a network to which the control plane device belongs, where the first message is used to instruct each forwarding plane device receiving the first message to send a topology discovery packet at all available ports of the forwarding plane device; receiving, by the control plane device, second messages respectively sent by the plurality of forwarding plane devices, where each of the second messages is generated, according to a first topology discovery packet received at a second port, by a second forwarding plane device sending the second message, and the first topology discovery packet is a topology discovery packet sent by a first forwarding plane device in the plurality of forwarding plane devices at a first port; and determining, by the control plane device, topology connections between the plurality of forwarding plane devices according to the second messages sent by the plurality of forwarding plane devices.