Packet Fragmentation Outer Header Overlay Tunnel
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Solution Overview
Problem
In software-defined networking environments, existing packet fragmentation methods lead to inefficiencies, particularly when packets larger than the maximum transmission unit size are fragmented, causing issues with flow identification and reassembly, resulting in dropped packets and performance degradation.
Innovation Solution
The system fragments packets into inner fragments, encapsulates them with an outer header, and inserts fragmentation information in a specific portion of the header, allowing tunnel endpoints to identify and reassemble the original packet without indicating fragmentation to devices in the path, ensuring seamless flow association and reassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If packets are fragmented using existing methods, then the packets can be transmitted over paths with smaller MTU, but flow identification and reassembly become problematic causing dropped packets
Solution Approach 1:
The packet is divided into multiple inner fragments that are then encapsulated with outer headers. Each fragment is a separate unit that can be transmitted independently through the network path with smaller MTU, while the outer header provides unified identification for reassembly at the destination.
Solution Approach 2:
The inner packet fragments are nested within outer headers to create encapsulated packets. This nested structure allows the fragmentation information to be carried within the outer header without exposing the fragmentation status to intermediate devices, enabling both small MTU traversal and reliable reassembly.
2Difficulty of detecting and measuring
If fragmentation information is indicated in the outer header, then tunnel endpoints can identify fragments for reassembly, but devices in the path may drop the packets
Solution Approach 1:
The outer header is designed with different properties for different purposes: it provides unified flow identification for tunnel endpoints while avoiding indication of fragmentation status to path devices. The header structure locally adapts its characteristics to serve tunnel endpoints without triggering harmful responses from intermediate devices.
Solution Approach 2:
The outer header acts as an intermediary that carries fragmentation information privately to tunnel endpoints without exposing this information to devices in the network path. This intermediary structure enables reassembly capability while preventing packet dropping by path devices that would otherwise see the fragmentation indicators.
3Productivity
If outer fragmentation is used, then packets can be transmitted, but services cannot detect that packets are fragments leading to performance degradation
Solution Approach 1:
The outer header serves multiple functions simultaneously: it provides flow identification for tunnel endpoints, carries fragmentation information for reassembly, and presents a unified appearance to path devices and services. This multi-functional design enables packet transmission while maintaining service processing efficiency by avoiding fragmentation indicators.
Data Source
AI summary
In some embodiments, a method fragments a first packet into a plurality of fragments when a length of an encapsulated first packet is larger than a maximum transmission unit size. For each fragment in the plurality of fragments, fragmentation information is generated. The method encapsulates each fragment in the plurality of fragments with an outer header to form a plurality of encapsulated packets. The respective fragmentation information for each fragment is inserted in a portion of the outer header that is processed by endpoints of an overlay tunnel and not processed by a device along a path of the overlay tunnel. The plurality of encapsulated packets are sent via the overlay tunnel.