Neighbor-Label Distribution Protocol for Backup Coverage
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Solution Overview
Problem
In computer networks, routers often lack effective backup coverage and load balancing due to the limitations of hop-by-hop Interior Gateway Protocol (IGP) paths, particularly in scenarios where loop-free alternate (LFA) paths are not viable, leading to inadequate traffic forwarding in case of link or node failures.
Innovation Solution
The extension of Label Distribution Protocol (LDP) to enable the distribution of neighbor-label mappings for directly connected neighbor routers, allowing traffic to be switched irrespective of hop-by-hop IGP paths, thereby improving backup coverage and load balancing by establishing segmented LSP tunnels using neighbor-labels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hop-by-hop IGP paths are used for traffic forwarding, then routing information is maintained accurately, but backup coverage is insufficient when LFA paths are not viable
Solution Approach 1:
The patent introduces neighbor-labels as an intermediary mechanism that enables direct traffic forwarding to neighbor routers without relying on traditional LFA paths. The neighbor-label mapping messages act as mediators that carry labeling information between LDP peers, allowing ingress routers to establish direct label-switched paths to neighbors even when metric-based LFA paths are unavailable. This resolves the contradiction by providing backup coverage through a different mechanism rather than through traditional metric-based routing.
Solution Approach 2:
The patent segments the traffic forwarding function into two independent components: (1) traditional IGP-based routing for path determination, and (2) neighbor-label-based forwarding for direct traffic delivery. By separating these functions, the system can maintain accurate routing information through IGP while simultaneously enabling flexible backup forwarding through neighbor-labels, thus resolving the contradiction between reliability and adaptability.
2Productivity
If traditional LFA paths based on link metrics are used, then loop-free routing is ensured, but load balancing is limited when alternative paths are unavailable
Solution Approach 1:
The neighbor-label mechanism serves as an intermediary that enables load balancing by providing alternative forwarding paths independent of IGP metrics. Multiple neighbor-labels can be distributed to different LDP peers, allowing the ingress router to distribute traffic across multiple neighbors for load balancing while each neighbor independently ensures loop-free delivery to its connected routers.
Solution Approach 2:
The patent adds a new dimension to routing by introducing neighbor-label-based forwarding that operates independently from the traditional metric-based IGP dimension. This creates a two-dimensional routing space where traffic can be balanced across multiple neighbors in one dimension while maintaining loop-free guarantees through the label-switched path mechanism in another dimension.
3Adaptability or versatility
If LDP label mappings are distributed hop-by-hop, then routing accuracy is maintained, but neighbor-label distribution requires extended protocol functionality
Solution Approach 1:
The patent makes LDP peers universal by enabling them to perform multiple functions: (1) traditional hop-by-hop label mapping distribution, and (2) neighbor-label mapping distribution to non-adjacent peers. The same LDP protocol infrastructure and message formats are used for both functions, reducing the need for separate complex mechanisms and minimizing additional device complexity while maximizing adaptability.
Data Source
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AI summary
Label Distribution Protocol (LDP) extensions are described that enable distribution of neighbor-label mappings for directly connected neighbor routers. A router capable of supporting the LDP extensions distributes neighbor-labels to be used by the router to label switch traffic destined for the directly connected neighbor router irrespective of a hop-by-hop Interior Gateway Protocol (IGP) path determined based on link metrics. In some examples, the neighbor-labels may increase backup coverage, e.g., link protection and/or node protection, in a network that, due to link metrics, does not have a viable loop-free alternate (LFA) path between an ingress router and an egress router of a label switched path (LSP). In other examples, the neighbor-labels may improve load balancing by enabling an ingress router in a first autonomous system (AS) to select a particular remote link on which to send traffic destined for remote routers in a second AS.