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Acee - From: Acee Lindem (acee) Hi Les, From: "Les Ginsberg (ginsberg)" <ginsberg@xxxxxxxxx>
That is not the use case - you are going to take the link down. It is not going to be the "link of last resort”, it is the currently the “link of last resort” and will imminently be taken down. [Les:]
https://tools.ietf.org/html/draft-ietf-ospf-link-overload-11#section-2 <snip> 2. Motivation … 4. Allow the link to be used as last resort link to prevent traffic disruption when alternate paths are not available. <end snip> This is the real value of the protocol extension. If the intention was to take the link out of service the extension would not be worth much as the behavioral difference between (normal
metric->max metric->down) vs (normal metric->down) is very small. This is also consistent with my recollection of the service providers motivation when the early versions of isis-reverse-metric were presented. The question was asked “why don’t you simply
take the link down?” and the response was “We don’t want to take the link down – we want it to be the link of last resort so that if all else fails we can still use the link to get to the node.” (As an aside, if the idea was to more gracefully redirect traffic away from the link in preparation for taking the link down you would need to use a metric offset as the isis-reverse-metric
draft does. Then you could direct traffic away from the link in incremental steps. I don’t mean to suggest this will be a common use case of reverse-metric – but it would at least be useful if the intent was to take the link down in a short while). Les
Agreed. Thanks, Acee
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