Hi Tony,
On 04/03/2019 18:54 , [email protected] 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.
I prefer (a) because of the faster convergence.
Adding all links on a single node to the flooding topology is not going
to cause issues to flooding IMHO.
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.
given that the flooding on the LAN in both OSPF and ISIS is done as
multicast, there is currently no way to enable flooding, either
permanent or temporary, towards a subset of the neighbors on the LAN. So
if the flooding is enabled on a LAN it is done towards all routers
connected to the it.
Given that all links between routers are p2p these days, I would vote
for simplicity and make the LAN always part of the FT.
thanks,
Peter
Thoughts? Comments? Flames?
Regards,
Tony
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