VPN Router PMTU Handling via Source Address Replacement
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Solution Overview
Problem
Existing group VPN implementations face challenges in effectively handling Path Maximum Transmission Unit (PMTU) messages due to address preservation techniques that can lead to packet size issues across different network paths, resulting in inefficient communication and additional processing overhead.
Innovation Solution
The proposed solution involves modifying address preservation techniques by including only the destination IP address in the outer IP header and using a new source IP address for encapsulation, allowing PMTU messages to be sent directly to the group member performing encapsulation, which then generates a new PMTU message with a reduced value to ensure packet size compliance with network path limits, and maintaining a database of PMTU values for efficient packet transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If address preservation techniques are used in group VPN implementations, then packet routing is simplified, but packet size issues occur across different network paths resulting in inefficient communication
Solution Approach 1:
The patent segments the address preservation function by separating the destination address (preserved for routing) from the source address (replaced with router's address). This allows PMTU messages to be properly routed to the encapsulating router while maintaining efficient packet forwarding for regular traffic.
Solution Approach 2:
The patent introduces the encapsulating router as an intermediary that receives PMTU messages intended for the original source, processes them, and generates new PMTU messages with correct size limits. This intermediary role resolves the conflict between simplified routing and proper PMTU message delivery.
2Ease of operation
If address preservation techniques are used in group VPN implementations, then packet routing is simplified, but additional processing overhead occurs due to PMTU message handling
Solution Approach 1:
The patent enables the encapsulating router to self-serve by directly receiving PMTU messages through its interface, eliminating the need for complex message forwarding mechanisms. The router independently processes these messages and generates appropriate responses, reducing processing overhead.
Solution Approach 2:
The patent performs preliminary encapsulation with the router's source address before packets traverse the network. This preliminary action ensures that PMTU messages are automatically directed to the correct router without requiring additional processing or message interception later in the transmission path.
3Speed
If packets are transmitted without size adjustment, then transmission speed is maintained, but packet size exceeds network path limits causing transmission failures
Solution Approach 1:
The patent implements a feedback mechanism where PMTU messages provide information about the maximum transmission unit size for each network path. The source device uses this feedback to adjust packet sizes before transmission, ensuring reliability while maintaining optimal transmission speed through the correct packet size selection.
Solution Approach 2:
The patent dynamically changes the packet size parameter based on PMTU information received from the network path. By adjusting this critical parameter, the system ensures packets fit within network path limits while maintaining efficient transmission, resolving the contradiction between speed and reliability.
Data Source
AI summary
Techniques are described herein for optimizing communications in a network. At a router in a virtual private network, a packet is received from a device in a subnetwork protected by the router. The router examines the packet to determine a source address that identifies the device and a destination address that identifies a destination network device for the packet. The router also analyzes the packet to determine a size of the packet and determines whether or not the size of the packet is larger than a maximum transmission unit size. If the size of the packet is larger than the maximum transmission unit size, the router encapsulates the packet with a header that includes the destination address and a new source address that identifies the router.