Multi-Segment Pseudo-Wire Connectivity Verification Using TTL Control
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Solution Overview
Problem
Current methods for verifying connectivity in multi-segment pseudo-wires (MS-PWs) are inefficient, as VCCV packets follow the same path as data packets, consuming processing capacity and time at each node, and there is a lack of effective end-to-end fault detection and diagnostic mechanisms for MS-PW services.
Innovation Solution
A method involving echo request and reply messages with a control word and a time-to-live (TTL) value set for the inner label, allowing only the terminating nodes to inspect and process VCCV messages, thereby reducing processing load on intermediate nodes and enabling effective end-to-end connectivity verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If VCCV packets follow the same path as data packets through all nodes, then connectivity verification is thorough, but processing capacity and time at each node is consumed
Solution Approach 1:
The patent segments the MS-PW into multiple sections and uses TTL values to control which nodes process VCCV packets. Different sections can be verified independently by different terminating nodes, dividing the verification workload and avoiding unnecessary processing at intermediate nodes while maintaining thorough connectivity verification for each segment.
Solution Approach 2:
The patent applies different processing rules to different nodes along the MS-PW path. Terminating nodes are configured to inspect and process VCCV messages based on TTL values, while intermediate nodes simply forward packets without inspection. This local differentiation reduces overall processing load while maintaining verification effectiveness.
2Difficulty of detecting and measuring
If all nodes inspect VCCV messages, then fault detection is comprehensive, but processing time increases
Solution Approach 1:
The patent sets TTL values in advance for VCCV packets before transmission. The TTL is configured to expire at specific terminating nodes, which triggers the inspection and processing of VCCV messages only at those predetermined locations. This preliminary configuration avoids time-consuming inspections at all nodes while ensuring comprehensive fault detection at critical points.
Solution Approach 2:
The patent uses TTL parameter changes to control VCCV packet processing behavior. As the TTL value decrements with each hop and reaches zero at specific terminating nodes, the packet processing behavior changes from simple forwarding to inspection and response. This parameter-based control enables comprehensive fault detection at key points without increasing overall processing time.
3Measurement precision
If VCCV messages are processed at every node, then connectivity verification is detailed, but line rate is reduced
Solution Approach 1:
The patent extracts the VCCV message processing function from intermediate nodes and concentrates it only at terminating nodes. Intermediate nodes perform only simple packet forwarding without inspection, maintaining line rate transmission speed. Terminating nodes perform detailed connectivity verification by inspecting VCCV messages when TTL expires, providing measurement precision without sacrificing transmission speed.
Data Source
AI summary
A method for testing connectivity of a multi-segment pseudo-wire (“MS-PW”) in a network, the method comprising: sending an echo request message from a first provider edge (“PE”) device to a second provider edge (“PE”) device for a section of the multi-segment pseudo-wire (“MS-PW”) between the first provider edge (“PE”) device and the second provider edge (“PE”) device; the echo request message being identified as such by a control word contained therein; an inner label of the echo request message having a time-to-live (“TTL”) value set to a number of segments in the section; the time-to-live (“TTL”) value for determining whether the control word is to be inspected as it traverses the section; upon the echo request message arriving at the second provider edge (“PE”) device, the second provider edge (“PE”) device recognizing the echo request message as such by inspecting the control word contained therein; and, receiving an echo reply message from the second provider edge (“PE”) device in response to the echo request message, the echo reply message confirming connectivity of the section.