Gateway MSS Adjustment for Tunnel Overhead
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Solution Overview
Problem
In extended layer two networks, the encapsulation of packets across multiple computing sites leads to issues with maximum transmission unit (MTU) sizes, particularly due to varying tunneling overheads caused by different encryption parameters, which can result in packet fragmentation and communication inefficiencies.
Innovation Solution
A gateway determines and updates the maximum segment size (MSS) values for Transmission Control Protocol (TCP) SYN packets based on tunneling overhead associated with encryption parameters, replacing the original MSS values to ensure accurate packet sizing across multiple tunnels, thereby preventing fragmentation and optimizing communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If gateways support multiple tunnels with different encryption parameters, then network connectivity and functionality are improved, but packet size management becomes complex due to varying tunneling overheads
Solution Approach 1:
The gateway applies different MSS values to packets traversing different tunnels based on their specific encryption parameters and overhead requirements. Each tunnel receives customized packet size management rather than a uniform approach, resolving the complexity of managing varying overheads across multiple tunnels.
Solution Approach 2:
The system dynamically adjusts the MSS parameter based on the encryption parameters and tunneling overhead of each specific tunnel. By changing the MSS parameter according to tunnel characteristics, the gateway optimizes packet transmission for each tunnel while maintaining overall system versatility.
2Device complexity
If gateways use common network interface for multiple tunnels, then device simplicity is improved, but accurate MSS determination becomes difficult due to shared interface
Solution Approach 1:
The gateway segments the packet processing by identifying which specific tunnel each packet should traverse, then applies the appropriate MSS value for that tunnel. This segmentation allows accurate MSS determination despite using a common network interface, as each packet is handled according to its destination tunnel's requirements.
Solution Approach 2:
The gateway acts as an intermediary that sits between the common network interface and the multiple tunnels. It receives packets on the common interface, determines the appropriate tunnel and MSS value, and then processes packets with the correct size parameters. This intermediary role resolves the conflict between interface simplicity and measurement precision.
3Productivity
If original MSS values from computing nodes are used, then processing speed is improved, but packet fragmentation occurs due to encapsulation overhead
Solution Approach 1:
The gateway performs preliminary adjustment of the MSS value before packet encapsulation and transmission through the tunnel. By calculating and applying the correct MSS value that accounts for tunneling overhead in advance, the system prevents packet fragmentation from occurring during transmission, thereby maintaining both processing efficiency and transmission reliability.
Solution Approach 2:
The gateway applies a preliminary correction to the MSS value to counteract the fragmentation problem that would otherwise occur during encapsulation. By preemptively adjusting the MSS to compensate for the overhead that will be added, the system prevents the harmful effect of fragmentation before it can occur, maintaining packet transmission integrity.
Data Source
AI summary
Described herein are systems, methods, and software to manage maximum segment size (MSS) values associated with multiple tunnels according to an implementation. In one implementation, a gateway may obtain a Transmission Control Protocol (TCP) synchronize (SYN) packet from a computing node. The gateway may identify a tunnel associated with the TCP SYN packet, determine a maximum segment size (MSS) value based on the overhead associated with the tunnel, and replace a first MSS value in the TCP SYN packet with the MSS value determined by the gateway. Once added, the gateway may encapsulate the TCP SYN packet and communicate the packet to a second gateway.