I concur with Stewart regarding a simple advice to the operator. In most cases a link that goes down will not repair itself without some external intervention.
And if we deal with a flapping link, it is a probkem by abd of itself, and probably should be disabled until the underlying problem is fixed.
My 2c,
Sasha Vainshtein
On Thu, Sep 21, 2017 at 11:21, Stewart Bryant<stewart.bryant@xxxxxxxxx> wrote:
The draft states that
" The proposed mechanism is limited to the link down event in order to
keep the mechanism simple."
Since a link that goes down will normally also come up again, the draft
ought to provide some guidance to the operator on how they should handle
that situation. Applications that care about the disruption caused by
microloops presumably have no care as to whether they are cause by link
up or link down, and so would prefer a complete elimination of that
disruption. However I accept that complete elimination has wider network
impact and that this approach which is really microloop mitigation has
utility.
The advice might be as simple as keeping the link out of service until a
quiet time, or the loss of connectivity has moved to the network to a
state of fragility such that disruption is acceptable.
- Stewart
On 20/09/2017 19:44, The IESG wrote:
> The IESG has received a request from the Routing Area Working Group WG
> (rtgwg) to consider the following document: - 'Micro-loop prevention by
> introducing a local convergence delay'
> <draft-ietf-rtgwg-uloop-delay-06.txt> as Proposed Standard
>
> The IESG plans to make a decision in the next few weeks, and solicits final
> comments on this action. Please send substantive comments to the
> ietf@xxxxxxxx mailing lists by 2017-10-04. Exceptionally, comments may be
> sent to iesg@xxxxxxxx instead. In either case, please retain the beginning of
> the Subject line to allow automated sorting.
>
> Abstract
>
>
> This document describes a mechanism for link-state routing protocols
> to prevent local transient forwarding loops in case of link failure.
> This mechanism proposes a two-step convergence by introducing a delay
> between the convergence of the node adjacent to the topology change
> and the network wide convergence.
>
> As this mechanism delays the IGP convergence it may only be used for
> planned maintenance or when fast reroute protects the traffic between
> the link failure time and the IGP convergence.
>
> The proposed mechanism is limited to the link down event in order to
> keep the mechanism simple.
>
> Simulations using real network topologies have been performed and
> show that local loops are a significant portion (>50%) of the total
> forwarding loops.
>
>
>
>
>
> The file can be obtained via
> https://datatracker.ietf.org/doc/draft-ietf-rtgwg-uloop-delay/
>
> IESG discussion can be tracked via
> https://datatracker.ietf.org/doc/draft-ietf-rtgwg-uloop-delay/ballot/
>
> The following IPR Declarations may be related to this I-D:
>
> https://datatracker.ietf.org/ipr/2565/
>
>
>
>
>
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