In-band Telemetry Path MTU Determination
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Solution Overview
Problem
Conventional path MTU discovery operations are time-consuming and fail when Layer 2 switch devices are involved, as they do not support ICMP fragmentation messages, leading to iterative and inefficient packet size adjustments.
Innovation Solution
An Information Handling System (IHS) with a processing system and memory that includes instructions for a Maximum Transmission Unit (MTU) size reporting engine, which generates and forwards a path MTU size discovery packet with an In-band Network Telemetry (INT) header, allowing switch devices to report their supported MTU sizes, enabling the determination of the lowest MTU size supported in the network path without iterative adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional path MTU discovery operations using ICMP fragmentation messages are used, then path MTU size can be determined for Layer 3 switch devices, but the operations are time-consuming and fail when Layer 2 switch devices are involved
Solution Approach 1:
The patent introduces an In-band Network Telemetry (INT) header as an intermediary mechanism to carry MTU size information from switch devices back to the source device. This INT header acts as a mediator that enables Layer 2 switch devices to participate in path MTU discovery without requiring ICMP support, thereby improving reliability and reducing discovery time by eliminating iterative operations
Solution Approach 2:
The patent changes the communication parameter from ICMP fragmentation messages (Layer 3 protocol) to INT headers embedded in data packets (Layer 2.5 telemetry). This parameter change allows MTU information to be conveyed in-band with data traffic, enabling both Layer 2 and Layer 3 switch devices to report their MTU capabilities efficiently in a single pass
2Adaptability or versatility
If iterative path MTU discovery operations are performed to accommodate Layer 2 switch devices with smaller MTU sizes, then path MTU can eventually be determined, but the process requires multiple packet transmissions and adjustments
Solution Approach 1:
The patent implements preliminary action by having switch devices along the network path proactively report their MTU sizes to the source device before data transmission begins. The INT header carries pre-collected MTU information from all switches in the path, allowing the source device to determine the path MTU in advance without iterative trial-and-error operations, thereby improving productivity
Data Source
AI summary
A path MTU size determination system includes a source host device that generates and transmits a path MTU size discovery packet. A plurality of switch devices in the path MTU size determination system provide a network path that couples a destination host device to the source host device. Each of the switch devices is configured to receive the path MTU size discovery packet transmitted by the source host device, provide a switch identity of that switch device and a MTU size supported by that switch device in a MTU size reporting header included in the MTU size discovery packet, and forward the path MTU size discovery packet. One of the switch devices will operate to determine a lowest MTU size in the MTU size reporting header, and another of the switch devices will cause the source host device to provide the lowest MTU size as its path MTU size.