Proxy Path MTU Detection for TCP Performance

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Solution Overview

Problem

Existing Performance Enhancing Proxies (PEPs) for computer networks face challenges such as high resource requirements, disruption to existing network protocols, and inefficiencies in handling varying network conditions, leading to performance limitations and increased latency.

Innovation Solution

A method is introduced to detect the maximum transmission unit (MTU) of a path between two performance enhancing proxies, allowing for dynamic repacketization and minimal latency, while maintaining compatibility with standard TCP/IP protocols and minimizing changes to existing network infrastructure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If PEPs are deployed as separate processing nodes to enhance TCP performance, then performance enhancement is achieved, but device complexity and resource overhead increase

Engineering Contradiction:

ImproveTCP performanceVSAvoidnetwork processing node

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent combines the PEP functionality with existing network infrastructure elements (routers, switches, or end systems) rather than deploying separate dedicated PEP nodes. This merging approach allows TCP performance enhancement to be achieved while avoiding the device complexity and resource overhead of standalone PEP processing nodes.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent enables existing network infrastructure to perform multiple functions - serving both as standard network routing/switching equipment and as PEP for TCP performance enhancement. This multi-functionality eliminates the need for dedicated PEP hardware, reducing overall device complexity while maintaining performance enhancement capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Productivity

If PEPs are deployed as separate processing nodes, then performance enhancement is achieved, but administrative overhead increases

Engineering Contradiction:

ImproveTCP performanceVSAvoidadministrative overhead

Core Design Contradiction:

ProductivityVSEase of operation

Solution Approach 1:

By merging PEP functionality into existing network infrastructure that is already deployed and managed, the patent eliminates the need for separate administrative management of PEP nodes. Network administrators continue to manage the same infrastructure elements they already oversee, reducing administrative overhead while achieving TCP performance enhancement.

Inventive Principle:

Principle #5Merging (Combining)

3Adaptability or versatility

If PEPs are inserted into software driver stacks, then integration is improved, but changes to operating system are required

Engineering Contradiction:

ImproveintegrationVSAvoidoperating system changes

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The patent employs an intermediary approach by implementing PEP functionality at the network infrastructure level rather than requiring modifications to end-system operating systems. This intermediary placement allows integration with TCP traffic flow without necessitating changes to operating system source code or requiring customized OS versions.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Productivity

If packet size is increased to improve bandwidth utilization, then throughput increases, but packet loss increases due to fragmentation

Engineering Contradiction:

Improvebandwidth utilizationVSAvoidpacket loss

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent performs preliminary Path MTU discovery before establishing data transmission. By determining the maximum transmission unit size in advance through probe packets with the DF flag set, the system identifies the largest packet size that can traverse the path without fragmentation. This preliminary action enables subsequent data packets to be sized appropriately, achieving high bandwidth utilization while preventing packet loss from fragmentation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements feedback mechanisms where ICMP messages regarding fragmentation are monitored and used to adjust packet sizing decisions. When fragmentation issues are detected through ICMP feedback, the system adapts its packet size selection to avoid problematic sizes, thereby reducing packet loss while maintaining optimal bandwidth utilization.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS7542471B2Method of determining path maximum transmission unit

Publication Date: 2009.06.02 CITRIX SYSTEMS INC

AI summary

Network endpoints using TCP/IP operate to determine the maximum transmission unit (MTU) of the path between them. This determination is done so as to avoid the expensive IP fragmentation that will occur when transitioning links with a smaller MTU size. The standard method of determining the path MTU (PMTU) has several known deficiencies, including: inefficient use of bandwidth as proper operation will likely result in the loss of one or more packets and difficulty of implementation as the reverse channel communication mechanism, reception of ICMP messages indicating the discarding of unfragmentable packets, is frequently blocked by firewalls and other security apparatus. A method of determining the PMTU between intermediate proxies is disclosed that does not require reception of ICMP messages or the inefficient use of bandwidth due to the presumed dropping of packets with valid data.