Hi Les, > Discussion of how to make BFD failure detection more robust belongs in the BFD WG > If you do not want the BFD session to come back up too quickly after a failure
Nothing I suggested is related to any of the above. Let me perhaps provide a very simple example. BFD being used is *AS*IS*. All the operator wants is to run it for say X sec without ever going down before bringing OSPF adj up. That timer and its consistency on both ends clearly belongs to OSPF not to BFD. Now what happens within those 30 sec, what BFD packets are formed and how they are exchanged is all BFD business - but I am not suggesting to include any of those in this draft. Do we have a common understanding so far ? Hint: Albert already stated that he needs that timer and that both vendors provided it via cfg. All that confirms is that timer is needed. All I am suggesting (even before being aware of the manual cfg for it) was to synchronize the value or pick lower configured between two peers. Kind regards, R. On Sat, Jan 29, 2022 at 9:08 PM Les Ginsberg (ginsberg) <ginsb...@cisco.com> wrote: > Robert – > > > > It is good that you take an active interest in this technology – but I > think the suggestions you are making should not be targeted at IGP use of > BFD. > > > > Discussion of how to make BFD failure detection more robust belongs in the > BFD WG – and – as you know – that WG has taken an interest in such problems > e.g., MTU. > > > > In regards to “dampening” = which I think is the relevant term for the > timer related suggestions you are making - this also does not belong in the > IGP. If you do not want the BFD session to come back up too quickly after a > failure, the proper place to put timers is either at the interface layer or > in the BFD implementation. > > I am familiar with implementations which apply this timer at the protocol > level (AKA BFD client in this context) and this is done precisely because > the protocol does NOT have the functionality being defined in this draft. > Once you have implemented “wait-for-BFD” logic as defined in this draft you > do not need additional delay timers in the protocol. > > > > I don’t think the suggestions you are making belong in this document. > > > > Les > > > > > > *From:* Lsr <lsr-boun...@ietf.org> *On Behalf Of * Robert Raszuk > *Sent:* Saturday, January 29, 2022 11:25 AM > *To:* Acee Lindem (acee) <a...@cisco.com> > *Cc:* Ketan Talaulikar <ketant.i...@gmail.com>; > draft-ietf-lsr-ospf-bfd-strict-m...@ietf.org; Albert Fu < > af...@bloomberg.net>; lsr <lsr@ietf.org> > *Subject:* Re: [Lsr] Working Group Last Call for "OSPF Strict-Mode for > BFD" - draft-ietf-lsr-ospf-bfd-strict-mode-04 > > > > Hi Acee, > > > > Can you suggest text which with you’d be happy? I’m sure the authors would > add you to the acknowledgements. > > > > Actually instead of suggesting any new text I would suggest to delete the > two below sentences and it will be fine: > > > > *"In certain other scenarios, a degraded or poor quality link will allow > OSPF adjacency formation to succeed* > > *but the BFD session establishment will fail or the BFD session > will flap. In this case, traffic that gets * > > *forwarded over such a link may experience packet drops while the failure > of the BFD session establishment * > > *would not enable fast routing convergence if the link were to go down or > flap."* > > > > This could be described but I don’t think it should be normative. This > begs the question as to why a hold down timer is not a part of the BFD > protocol itself. > > > > There is one - BFD calls it multiplier. > > > > But the timer I am suggesting is not related to BFD operation, but to OSPF > (and/or ISIS). It is not about BFD sessions being UP or DOWN. It is about > allowing BFD for more testing (with various parameters (for example > increasing test packet size in some discrete steps) before OSPF is happy to > bring the adj. up. > > > > Thx, > > R. >
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