ISIS LSP Flooding via Distribution Tree
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In large-scale networks, the periodic updates of Link State Protocol Data Units (LSPs) under the Intermediate System to Intermediate System (ISIS) routing protocol lead to excessive resource occupation, causing network bandwidth and CPU usage issues due to redundant LSP packet synchronization, which affects network performance.
Innovation Solution
The method involves designating a pre-appointed Intermediate System as the tree root, computing an unpruned distribution tree using the Shortest Path First (SPF) algorithm, and classifying LSP packets as important or unimportant to optimize flooding along the distribution tree, reducing redundant sending from unnecessary interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LSP packets are periodically updated and flooded on all interfaces, then IP reachability information is synchronized across the network, but network bandwidth resources are excessively occupied and CPU resources are overwhelmed
Solution Approach 1:
The patent segments LSP packets into two categories: those containing topology information (Level-1 LSPs, Level-2 LSPs with neighbor TLV) and those containing only IP reachability information (Level-1 LSPs with non-zero IP prefix length). Different flooding strategies are applied to each segment, with topology-critical packets flooded on all interfaces and reachability-only packets flooded selectively based on distribution trees, thereby reducing overall bandwidth consumption while maintaining synchronization reliability
Solution Approach 2:
The patent implements local quality by applying different flooding behaviors to different types of LSP packets based on their content characteristics. Packets containing topology information are flooded universally on all interfaces to ensure network-wide consistency, while packets containing only IP reachability information are flooded selectively along pre-computed distribution trees, optimizing bandwidth usage according to the specific needs of each packet type
2Loss of information
If LSP packets are flooded on all interfaces, then complete network topology information is distributed, but CPU resources are excessively occupied and Hello keep-alive packets cannot be sent in time
Solution Approach 1:
The patent segments the flooding process based on LSP packet content, separating topology-critical packets from reachability-only packets. This segmentation allows the system to process and flood only the necessary packets on all interfaces, reducing CPU overhead while maintaining complete topology information distribution through selective flooding of Level-1 LSPs and Level-2 LSPs with neighbor TLV
Solution Approach 2:
The patent performs preliminary action by pre-computing distribution trees before LSP flooding. The SPF algorithm is executed in advance to establish optimal flooding paths, and these pre-computed trees are stored for subsequent use. This preliminary computation reduces real-time CPU processing requirements during LSP flooding operations, allowing Hello keep-alive packets to be sent timely while still achieving complete topology information distribution
3Speed
If SPF algorithm computes distribution tree for each LSP update, then optimal flooding paths are determined, but excessive computation time is consumed
Solution Approach 1:
The patent applies preliminary action by computing the distribution tree once using the SPF algorithm and storing it for repeated use during LSP flooding operations. Instead of re-computing the distribution tree for each LSP update, the pre-computed tree is retrieved and applied, significantly reducing computation time while maintaining optimal flooding paths for rapid LSP propagation
Solution Approach 2:
The patent implements partial action by computing only the necessary distribution tree once, rather than performing full SPF computation for each LSP update. The pre-computed distribution tree provides sufficient information for efficient LSP flooding without requiring excessive re-computation, achieving the right balance between flooding speed and computation time
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Disclosed are an ISIS-based flooding method and device, herein the method includes: an IS in a network topology taking a pre-appointed IS in the network topology as a tree root, and executing an SPF algorithm to compute an unpruned distribution tree that reaches all ISs in the network topology; and the IS in the network topology performing flooding on an LSP packet along the distribution tree. Through the present invention, the problem that excessive resources are occupied by LSPs in the existing technology is solved, the redundant sending from unnecessary interfaces during synchronization of a great number of LSPs is eliminated, the overall data stream load of a network is reduced, the processing resources occupied by an IS device to send a great number of LSPs from all interfaces are reduced and the overall performance of the IS device is improved.