Public Network Forwarding Device TRACE Detection
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Solution Overview
Problem
In IP address tunnel forwarding networks, the source Customer Edge (CE) cannot detect public network forwarding devices due to response messages being sent only to the head node of the public network IP tunnel, making it difficult to establish a clear data transmission network topological graph.
Innovation Solution
A method and device for detecting public network forwarding devices, where a TRACE message is received, analyzed for the Hop Limit (HL) value, and a response message is generated with the source IP set as the public network forwarding device's IP, allowing the message to be encapsulated and sent back to the source CE, enabling detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If response messages are sent only to the head node of the public network IP tunnel, then the tunnel forwarding mechanism is simplified, but the source CE cannot detect public network forwarding devices
Solution Approach 1:
The patent introduces an intermediary mechanism where the PE device acts as a mediator to forward detection response messages from the tunnel head node back to the source CE. The PE device receives the response message at the tunnel head, extracts the source CE identifier, and forwards a new response message back through the tunnel to the source CE, enabling detection without changing the original tunnel forwarding simplification.
2Loss of information
If the source CE sends TRACE messages through the PE to public network forwarding devices, then topological graph establishment is enabled, but response messages cannot reach the source CE
Solution Approach 1:
The patent applies inversion by reversing the traditional response message path. Instead of the response message following the same tunnel path back to the source CE, the response is generated at the tunnel head node and sent back through the PE device using a different path - specifically, the PE device reconstructs and forwards the response message back through the tunnel to the source CE, ensuring reliable delivery.
3Adaptability or versatility
If outer layer encapsulation is used for TRACE messages in the public network, then protocol compatibility is improved, but the source IP identification becomes complex
Solution Approach 1:
The patent applies preliminary action by having the PE device extract and store the source CE identifier (inner IP address) before forwarding the encapsulated TRACE message through the tunnel. This pre-extraction and storage of identification information simplifies the subsequent response message routing, as the PE device already has the source identifier ready when the response needs to be sent back.
Data Source
AI summary
Provided are a method for detecting a public network forwarding device receiving a TRACE message performed by outer layer encapsulation based on a preset protocol, and analyzing an HL value from the outer layer encapsulation; analyzing the TRACE message if the HL value indicates that the last hop has been reached, and acquiring a source IP carried in the TRACE message; generating a response message, setting a destination IP in the response message as the source IP in the TRACE message, and setting a source IP in the response message as an IP of a public network forwarding device; and performing outer layer encapsulation on the response message based on the preset protocol, respectively setting the source IP and the destination IP in the outer layer encapsulation of the response message as the source IP and a destination IP in the outer layer encapsulation of the TRACE message.