SDN Controller MTU Installation for Network Traffic
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Solution Overview
Problem
Existing computer network systems face inefficiencies and increased load due to repeated packet fragmentation and Path Maximum Transmission Unit (MTU) Discovery processes, which can lead to network congestion and security issues when handling large packets, especially when fragmentation is not permitted or when error messages are blocked by security devices.
Innovation Solution
An SDN controller determines the MTU size for each link along a datapath, selects the largest allowable MTU size, and installs it on controlled nodes, reducing fragmentation, network traffic, and the risk of denial-of-service attacks by minimizing the number of nodes handling MTU Discovery packets and avoiding black hole connections caused by security devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Path MTU Discovery is performed to determine the maximum MTU size for a datapath, then the network can avoid black hole connections and improve reliability, but it generates excessive network traffic and increases processor load on switches
Solution Approach 1:
The SDN controller performs MTU determination in advance by sending probe packets through the datapath before actual data transmission. The controller collects MTU information from all links along the datapath and calculates the maximum allowable MTU size beforehand, storing this information for future use. This preliminary action eliminates the need for repeated PMTU discovery processes, reducing network traffic and processor load while maintaining reliability.
2Adaptability or versatility
If packet fragmentation is permitted to handle packets larger than MTU size, then network adaptability is improved, but repeated fragmentation along the datapath increases processor load and decreases network efficiency
Solution Approach 1:
The system determines the maximum MTU size for the entire datapath in advance by identifying the minimum MTU among all links. This information is stored and used to guide packet transmission decisions before actual data flow occurs. By knowing the bottleneck MTU size beforehand, the network can prevent fragmentation by adjusting packet sizes at the source, thereby maintaining adaptability while avoiding the efficiency losses associated with repeated fragmentation.
3Productivity
If the SDN controller determines and installs the largest allowable MTU size on controlled nodes, then packet fragmentation is reduced and network efficiency is improved, but the controller must maintain and query MTU information for all nodes
Solution Approach 1:
The SDN controller consolidates MTU information from all network nodes and datapaths into a centralized database. By merging this information at the controller level, the system eliminates the need for individual nodes to independently track and manage MTU sizes for multiple datapaths. The controller uses this consolidated information to determine optimal MTU sizes and install them on relevant nodes, improving network efficiency while managing complexity centrally rather than distributed across all devices.
Data Source
AI summary
In some examples, a maximum transmission unit (MTU) is installed by a Software-Defined Network (SDN) controller on a controlled network node for traffic along a datapath in an SDN. The installed MTU can, for example, be selected from MTU sizes in an MTU database for nodes along the datapath. For example, the installed MTU can be selected as the largest allowable MTU size based on the nodes of the datapath.