Re: [Lsr] Temporary addition of links to flooding topology in dynamic flooding

Hi Robert,

On 11/03/2019 22:28 , Robert Raszuk wrote:
> Hi,
>
> As of now at the event of failure of any of the FT enabled link
> additional links are being added in more or less random fashion by nodes
> directly connected to the failed links.

above statement is incorrect. It is absolutely NOT TRUE that "at the 
event of failure of any of the FT enabled link additional links are 
being added".

Temporary additions of the links to the FT has its strict rules:

6.7.5. Failures of Link On the Flooding Topology

   "If the failed local link represented the only connection to the
    flooding topology on the node where the link failed, the node MUST
    enable temporary flooding on a subset of its local links."

6.7.9.  Treatment of Disconnected Adjacent Nodes

    Every time there is a change in the flooding topology a node MUST
    check if there are any adjacent nodes that are disconnected from the
    current flooding topology.  Temporary flooding MUST be enabled
    towards a subset of the disconnected nodes.

So we are only performing temporary flooding if either we or one of our 
neighbors got isolated from the FT, which given the bi-connectivity of 
the FT itself is an unlikely event.

thanks,
Peter

>
> In the event of 100s of links on such nodes and advisable rate limiting
> addition of those links it seems that repair of FT may take some time.
>
> In order to reduce such time interval better then random addition of
> remaining links seems recommended. How about we hint participating nodes
> to execute purely in control plane of FT an LFA algorithm for possible
> future event of active link failure and use results of the LFA
> computation to prioritize links which will be first temporary additions
> upon active flooding links failures ?
>
> Such optimization is local and optional and does not require any changes
> to proposed protocol signalling.
>
> _Therefor how about just one sentence addition to section 6.7.1
> of draft-ietf-lsr-dynamic-flooding:_
>
> /Temporary additions of links to flooding topology could be more
> educated if given node runs a pure control plane LFA ahead of any FT
> failure on active FT links completely detached from potential LFA runs
> for data plane topology. /
>
> Kind regards,
> R.
> /
> /
>
>
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