L2 Multicast Path Tracing via Augmented Response Blocks
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Solution Overview
Problem
Current multicast tracing technologies, such as Mtrace, are limited to Layer 3 (L3) networks and cannot provide information about Layer 2 (L2) switches, which are common in campus multicast networks, leading to incomplete path tracing and difficulties in monitoring multicast network performance.
Innovation Solution
The implementation of L2-enhanced multicast path tracing, where the Last-Hop Router (LHR) performs both L3 Mtrace and L2 multicast trace operations, using Augmented Response Blocks (ARBs) to gather information from L2 switches and client devices, and aggregates this data to provide a complete multicast path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If Mtrace is used for multicast path tracing, then L3 network path information can be obtained, but L2 switch information is missing and path tracing is incomplete
Solution Approach 1:
The patent creates a universal tracing mechanism that operates across both L3 and L2 networks. The LHR performs dual operations: L3 Mtrace for router path information and L2 multicast trace for switch information. This multi-functional approach allows a single tracing system to gather comprehensive path information across different network layers, making the system adaptable to both L3 and L2 environments.
Solution Approach 2:
The patent divides the tracing process into two distinct segments: L3 Mtrace operation for obtaining router path information and L2 multicast trace operation for obtaining switch information. By segmenting the tracing function into layer-specific operations, the system can collect information from different network layers independently and then aggregate them into a complete path trace, resolving the information loss problem.
2Loss of information
If L2-enhanced multicast path tracing is implemented, then complete path information including L2 switches is obtained, but system complexity increases due to dual L3 and L2 operations
Solution Approach 1:
The patent merges the L3 Mtrace operation and L2 multicast trace operation into a unified L2-enhanced multicast path tracing process. The LHR coordinates both operations, aggregates their results, and presents a complete path trace to the client. This merging approach consolidates multiple tracing mechanisms into a single system interface, reducing the apparent complexity for users while maintaining comprehensive tracing capabilities.
Solution Approach 2:
The LHR acts as an intermediary that manages the complexity of dual L3 and L2 operations. It receives the trace query from the client, initiates both L3 Mtrace and L2 multicast trace operations, collects results from both domains, and aggregates them into a unified response. This intermediary role shields the client from the underlying complexity while enabling complete path tracing.
3Reliability
If dual L3 Mtrace and L2 multicast trace operations are performed, then comprehensive diagnostics are enabled, but processing time and resources increase
Solution Approach 1:
The patent performs preliminary actions by having the LHR initiate both L3 Mtrace and L2 multicast trace operations simultaneously or in an optimized sequence, rather than sequentially. The LHR prepares the trace request to be processed across both layers, and coordinates the aggregation of results. This preliminary coordination reduces the total tracing time compared to performing separate sequential traces, while maintaining comprehensive diagnostic reliability.
Data Source
AI summary
During operation, a layer-3 (L3) router can receive a trace query to trace multicast paths associated with a multicast group. In response to detecting a layer-2 (L2) switch coupled to the L3 router, the L3 router can construct a request packet and send the request packet to the coupled L2 switch. The request packet comprises a first data block indicating that the request packet is an L2 multicast trace request, thereby causing the L2 switch to propagate the request packet to downstream L2 switches until the request packet reaches a last-hop L2 switch. The L3 router can receive, from the last-hop L2 switch, a reply packet responsive to the L2 multicast trace request, the reply packet comprising one or more data blocks, with each data block comprising information about an L2 switch or client device present on a traversed multicast path for the multicast group.