Re: [Lsr] New Version Notification for draft-wang-lsr-prefix-unreachable-annoucement-03.txt

[Robert Raszuk <[e-mail]>]

Hi,

Imagine I have two ABRs connecting area 1 to area 0. One is signalling
transition to down for subset of summary and the other does not .. maybe it
is slow ... maybe it does not support this new feature.

So all routers in the area 0 are receiving a full summary from one ABR and
a summary with hole from the other one. Should that be logical AND or OR ?

Then on the other side there is area 2. Should the transition to down be
leaked ? If so in a nicely stable network we may see instead of few /20
summaries jump to 1M transitions to down yet summary continues - would that
not have a bit negative effect on the entire network ? Where would ABR
remove summary itself - when all atomic routes subsumed by the summary
transition to down ?

- - -

I am supportive of the idea to signal unreachable network elements. But I
am not sure if we should do it in IGP and BGP or only in BGP.

Thx,
R.


On Thu, Jul 30, 2020 at 6:08 PM Huzhibo <[e-mail]> wrote:

> HI acee：
>
> PUA does not advertise reachable or unreachable details, it advertise
> events with prefix from up to down.
>
>
> thanks
>
> Zhibo
>
>
>
>
> --------------------------------------------------
> 胡志波 Hu Zhibo
> Mobile: [phone]
> Email: [e-mail]
> *发件人：*Acee Lindem (acee) <[e-mail]>
> *收件人：*Peter Psenak <ppsenak=[e-mail]>;Robert Raszuk <
> [e-mail]>
> *抄 送：*Aijun Wang <[e-mail]>;Xiaoyaqun <[e-mail]>;Huzhibo
> <[e-mail]>;Aijun Wang <[e-mail]>;lsr <
> [e-mail]>
> *时 间：*2020-07-31 00:04:02
> *主 题：*Re: [Lsr] New Version Notification for
> draft-wang-lsr-prefix-unreachable-annoucement-03.txt
>
> So, how do we define a reachable route - is it any route subsumed by the
> summary LSA that we knew about in the past that becomes unreachable? When
> the PUA is withdrawn, how do we know whether it is because of expiration of
> the interval or the route becoming reachable again? This is a slippery
> slope.
> Thanks,
> Acee
>
> On 7/30/20, 10:34 AM, "Lsr on behalf of Peter Psenak" <
> [e-mail] on behalf of ppsenak=[e-mail]>
> wrote:
>
>     On 30/07/2020 16:30, Robert Raszuk wrote:
>     > Hey Peter,
>     >
>     > Not sure how smart you really want to be here but keep in mind that
> BGP
>     > say option C may never hear about it all the way to the egress PE in
>     > other domain or area ... It is almost always incongruent with IGP.
>     >
>     > So if the BGP path is installed it will indeed be at risk to resolve
> via
>     > less specific when it is still active BGP path and you too quickly
>     > remove info about unreachability.
>
>     again, if you are smart you can use this info to your advantage, even
>     without putting it in the forwarding and leaving the less specific
> stuff
>     intact.
>
>     Peter
>
>
>     >
>     > Thx
>     > R.
>     >
>     > On Thu, Jul 30, 2020 at 4:21 PM Peter Psenak <[e-mail]
>     > <mailto:[e-mail] <[e-mail]>>> wrote:
>     >
>     >     On 30/07/2020 16:14, Robert Raszuk wrote:
>     >      >      > 2：For bgp example，when the pe node down，the bgp peer
>     >     must down
>     >      >     within
>     >      >      > 30 mintus，It will not get it up via cancle advertise
> pua.
>     >      >
>     >      >     for the above it is sufficient to advertise the
>     >     unreachability for few
>     >      >     seconds from each ABR independently. That would be a much
>     >     more solid
>     >      >     proposal.
>     >      >
>     >      >
>     >      > Not sure about "few seconds" ... IBGP def hold time in number
> of
>     >      > implementations is 180 sec :) .. but few minutes will work
> for sure.
>     >
>     >     depends how you use it.
>     >
>     >     If you can use the unreachable info in a smart way, it's
> sufficient if
>     >     it is present for a very short time interval.
>     >
>     >     thanks,
>     >     Peter
>     >
>     >      >
>     >      > Thx,
>     >      > R.
>     >      >
>     >
>
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