Re: [Lsr] Fwd: Open issues with Dynamic Flooding

["Les Ginsberg (ginsberg)" <[e-mail]>]

Tony -

Here is my take.

Regarding Issue #2 below, we had a healthy thread on this since Prague and I believe have consensus that we WILL support LANs in the encoding of the flooding topology (centralized mode). Authors need to agree on changes to the draft which we will take offline and then publish an update.

Regarding Issue #1 below, we did have a thread on this BEFORE Prague and seemed to reach consensus on:

<snip>
Let me propose that we add something to sections 6.7.5, 6.7.9, and 6.7.11 like:

Addition of temporary flooding should be done with caution, as the addition of excessive connectivity to the flooding topology may trigger unwanted behavior. Routers SHOULD add temporary flooding in a rate limited manner, if not configured otherwise.

<end snip>

(See attached email)

Again, authors need to address this in the next draft revision but I believe we have agreement in principle.

So I think we can consider these matters resolved - pending WG feedback on the updated draft whenever it becomes available.

   Les


> -----Original Message-----
> From: Lsr <[e-mail]> On Behalf Of [e-mail]
> Sent: Monday, April 08, 2019 7:27 AM
> To: [e-mail]
> Subject: [Lsr] Fwd: Open issues with Dynamic Flooding
> 
> 
> Hi all,
> 
> It’s been another week and we’ve had a few more very interesting
> conversations, but we seem to have not moved very far.
> 
> Have we converged?
> 
> Tony
> 
> 
> 
> > Hi all,
> >
> > I hope that everyone had a safe and uneventful trip home from Prague and
> that no one else had the seat right in front of the screaming baby.  ;-)
> >
> > I would like to re-open the discussion on the mailing list. Based on the off-
> line discussions that I had with folks, I believe that we’re leaning towards
> including the LANs in the signaling and rate limiting link addition during repair.
> >
> > Dissent? Discussion?
> >
> > Tony
> >
> >
> >> On Mar 4, 2019, at 9:54 AM, [e-mail] wrote:
> >>
> >>
> >> Hello,
> >>
> >> There are still two issues that need to be discussed and I was hoping that
> we could make progress on the mailing list before Prague.
> >>
> >> 1) Temporary additions to the flooding topology
> >>
> >>   There are several cases where we would like to make temporary
> additions to the flooding topology: repairing a partition of the flooding
> topology or adding a node to the base topology for the first time. We can:
> >>
> >>   (a) Temporarily add all of the links that would appear to remedy the
> partition. This has the advantage that it is very likely to heal the partition and
> will do so in the minimal amount of convergence time.
> >>
> >>   (b) For each node adjacent to the partition, add no more than a single
> link across the partition.  If that does not repair the partition in a while (LSP
> propagation time + SPF time), then add another link.
> >>        Iterate as necessary. This has the advantage that it minimizes the risk
> of creating a cascade failure.
> >>
> >> 2) Inclusion of pseduonodes in the System IDs TLV
> >>
> >>   In the general case, a topology can include LANs. If a LAN is in parallel
> with a P2P link, the Area Leader cannot currently distinguish between the
> two links. This can be of importance if there are other
> >>   systems also on the LAN that should be using their LAN interface for
> flooding.
> >>
> >>   We propose to change the System IDs TLV to include a pseudo-node ID
> as well as the system ID.  It would also make sense to rename the TLV to be
> the “IS-IS Area Node IDs TLV”.
> >>
> >>   Behaviorally, we should add a requirement that if the Area Leader
> includes a pseudonode in the flooding topology, then all systems with an
> adjacency on that LAN should use the LAN as part of the
> >>   flooding topology, whether or not they are explicitly listed as adjacent to
> the LAN in the Flooding Path TLV.
> >>
> >> Thoughts? Comments? Flames?
> >>
> >> Regards,
> >> Tony
> >>
> >
> 
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--- Begin Message ---

>> I agree that optimal is probably unknowable. The question then is what
>> do we say in the document?  How about something about rate limiting?
> 
> yes, something of that nature, with possible config option.


Let me propose that we add something to sections 6.7.5, 6.7.9, and 6.7.11 like:

Addition of temporary flooding should be done with caution, as the addition of excessive connectivity to the flooding topology may trigger unwanted behavior. Routers SHOULD add temporary flooding in a rate limited manner, if not configured otherwise.


> the trick is that "all" nodes would comply, where we may only need one/subset to do...


This is the addition of one link, and in particular the onus is really on the DIS to drive synchronization.  Per your above arguments, I’m comfortable with this.

Tony

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--- End Message ---