WAN Edge Router MTU Synchronization via Inter-Switch Link Feedback
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Solution Overview
Problem
In computer networks with WAN edge routers that provide redundancy, MTU mismatches lead to packet loss due to the lack of effective mechanisms for negotiating and configuring desired MTU on inter-switch links, especially in high availability systems, resulting in increased network traffic and reduced efficiency.
Innovation Solution
A system and method for synchronizing MTU values between network devices in high availability systems, using modules for interface determination, layer-3 MTU determination, synchronization, highest layer-3 MTU determination, layer-2 MTU determination, and inter-switch link configuration to ensure consistent MTU settings across network devices, preventing packet drops and optimizing network performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If router redundancy is implemented at WAN edge, then reliability is improved, but MTU mismatch causes packet loss
Solution Approach 1:
The patent implements a feedback mechanism where the first network device determines its layer-3 MTU value and sends this information to the second network device. The second network device receives this MTU value and configures its inter-switch link accordingly. This feedback loop ensures that both devices have consistent MTU settings, preventing packet loss while maintaining router redundancy for improved reliability.
2Object-generated harmful factors
If path MTU discovery is used, then packet loss is prevented, but network traffic increases
Solution Approach 1:
The patent applies preliminary action by having the first network device proactively determine and communicate its layer-3 MTU value to the second network device before any packet transmission issues occur. This advance configuration allows the second network device to set its inter-switch link MTU appropriately in advance, preventing packet loss without requiring additional path MTU discovery traffic or fragmentation handling during normal operation.
3Object-generated harmful factors
If IP fragmentation is implemented, then packet loss is reduced, but network efficiency decreases
Solution Approach 1:
The patent introduces an intermediary mechanism where MTU information is exchanged between network devices through a dedicated communication channel. The first network device acts as an intermediary that communicates its MTU capabilities to the second network device, which then configures its inter-switch link accordingly. This intermediary approach eliminates the need for IP fragmentation by ensuring proper MTU configuration, thereby maintaining network efficiency while preventing packet loss.
Data Source
AI summary
One embodiment can provide a method and system for synchronizing MTU in a WAN edge with router redundancy. During operation, the system may determine a set of interfaces associated with a network device among a plurality of network devices coupled via inter-switch links. The system can determine a set of layer-3 MTU values corresponding to the set of network interfaces and can determine a highest layer-3 MTU value based on the set of determined layer-3 MTU values. The system can synchronize, via the inter-switch links, the highest layer-3 MTU value, resulting in a set of highest layer-3 MTU values at the network device. The system can determine, based on the set of highest layer-3 MTU values, a global highest layer-3 MTU value. The system can derive a layer-2 MTU value based on the global highest layer-3 MTU value and can configure a respective inter-switch link with the layer-2 MTU value.