Inter-area LDP Node Protection via Bypass LSP
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Solution Overview
Problem
Traditional link state protocols in computer networks take a long time to adapt to link and node failures, leading to delays in traffic rerouting and potential packet loss due to the need for each router to recalculate the shortest path.
Innovation Solution
Implementing a point of local repair (PLR) network device that uses Interior Gateway Protocol (IGP) topology information to automatically establish a bypass Label Switched Path (LSP) and targeted LDP session, allowing for intra-area and inter-area node protection without requiring extensions to the Label Distribution Protocol (LDP).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional link state protocols are used for routing, then routing information can be exchanged and topology can be maintained, but convergence time is long and packet loss occurs during failure recovery
Solution Approach 1:
The patent pre-computes and establishes bypass LSPs (Label Switched Paths) before any failure occurs. The PLR (Point of Local Repair) router identifies backup next-hop routers and establishes alternative paths in advance, so when a failure happens, traffic can be immediately redirected without waiting for full convergence. This preliminary action eliminates the convergence delay problem.
Solution Approach 2:
The patent segments the backup path computation into different scopes: intra-area bypass LSPs for failures within the same IGP area, and inter-area bypass LSPs for failures involving area border routers. This segmentation allows more targeted and efficient backup path establishment, improving reliability without requiring complete network re-computation.
2Reliability
If bypass LSPs are established for node protection, then packet loss is reduced during failure, but device complexity increases due to additional LDP sessions and topology processing
Solution Approach 1:
The PLR router automatically identifies backup next-hop routers and establishes bypass LSPs without requiring manual configuration or external control. The router uses its own IGP topology information to autonomously compute and set up protection paths, reducing operational complexity while improving reliability.
Solution Approach 2:
The patent makes the PLR router handle multiple functions: it processes IGP topology information, identifies protected nodes, computes backup paths, establishes LDP sessions, and manages both intra-area and inter-area bypass LSPs. This multi-functionality consolidates complexity into a single device role rather than requiring multiple specialized components.
3Adaptability or versatility
If node protection is implemented in all network topologies, then fast reroute is available more widely, but LDP protocol complexity increases
Solution Approach 1:
The patent uses IGP (Interior Gateway Protocol) topology information as an intermediary to enable LDP node protection. Instead of modifying LDP directly to handle all protection logic, the system leverages existing IGP routing data to identify backup paths and establish LDP sessions. This intermediary approach allows node protection to work in most topologies without adding complex protocol extensions to LDP.
Data Source
AI summary
Techniques are described for providing fast reroute inter-area node protection for label switched paths (LSPs) using label distribution protocol (LDP). In one example, a network device may be configured to determine that a protected node is an area border router, and use network topology information, obtained by an Interior Gateway Protocol (IGP) executing on the network device, to identify a second area border router in the same IGP area as the protected node, to which to automatically establish a bypass LSP and a targeted LDP session.