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/