Hi Dave, Thank you for your observations. My explanations are inline below with prefix [HC].
>From: David Allan I [mailto:[email protected]] >Sent: Friday, April 12, 2019 8:57 AM >To: Huaimo Chen <[email protected]>; [email protected] >Cc: [email protected] >Subject: RE: [Lsr] Min Links for Multiple Failures on Flooding Topology > >Hi > >A couple of quick observations…. > 1) The alternate backup path would appear to also require the criteria of being link diverse with the FT if the goal is to protect against multiple failures. [HC]: Can you give some more details about this? 2) If node failures are considered, I’m not sure what criteria is used to deem a backup path as useful….. [HC]: Regarding to the failure of a node X on the FT, suppose that there are multiple (i.e., two or more) nodes that were connected to the failed node X through the links on the FT. For each pair of these multiple nodes, a backup path between this pair is computed and enabled for temporary flooding. Thus the backup paths will connect these multiple nodes on the FT, and the FT partition caused by multiple failures including the failure of node X is fixed through the backup paths for the failed node X and the backup paths for the other failures. For example, if the failed node X was connected to two nodes Ri and Rj (assume that Ri’s ID < Rj’s ID) by the links on the FT before node X fails, there is only one pair of nodes: (Ri, Rj). A unique backup path from Ri to Rj is computed and enabled for temporary flooding. This backup path will connect Ri and Rj on the FT and fix the FT partition caused by multiple failures with the backup paths for the other failures. In another example, if the failed node X was connected to three nodes Ri, Rj and Rk (assume that Ri’s ID < Rj’s ID < Rk’s ID) by the links on the FT before node X fails, there are three pairs of nodes: (Ri, Rj), (Ri, Rk) and (Rj, Rk). A unique backup path from Ri to Rj, a unique backup path from Ri to Rk, and a unique backup path from Rj to Rk are computed and enabled for temporary flooding. These three backup paths will connect three nodes Ri, Rj and Rk on the FT, and fix the FT partition caused by multiple failures with the backup paths for the other failures. Best Regards, Huaimo >Hope this helps >Dave
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