Dynamic Flooding on Dense Graphs
draft-ietf-lsr-dynamic-flooding-18

# Internet AD comments for draft-ietf-lsr-dynamic-flooding-17
CC @ekline

* comment syntax:
  - https://github.com/mnot/ietf-comments/blob/main/format.md

* "Handling Ballot Positions":
  - https://ietf.org/about/groups/iesg/statements/handling-ballot-positions/

## Comments

### S4

* Just as an observation: a diagram or two might have been helpful (if any
  are actually usefully expressible in our publication format(s)).

# Gunter Van de Velde, RTG AD, comments for draft-ietf-lsr-dynamic-flooding-17
# Intended RFC status: Experimental

Thank you for the work put into this document. This document is a joy to read and documents an elegant solution to a well known IGP problem problem space.

Please find https://www.ietf.org/blog/handling-iesg-ballot-positions/ documenting the handling of ballots.

Special thanks to Acee Lindem for the shepherd's write-up and to Sue Hares for the Routing Directorate review.

before jumping into some idnits and comment review details, i wanted to express that it was entertaining to read about terminology used within  graph theory discussing Hamiltonian cycle, bipartite graph, K5,9 etc. 

Please find some observations and COMMENTS which appeared during my ballot review process. I hope it can help or contribute with the quality of the draft-ietf-lsr-dynamic-flooding-17 document.

409	   Similarly, if additional redundancy is added to the flooding
410	   topology, specific nodes in that topology may end up with a very high
411	   degree.  This could result in overloading the control plane of those

The text reads smooth, until the term 'degree' pops up without explanation what it entails. I (non-native English speaker) suspect it is terminology from graph theory. I do recall it being mentioned within the presentations about this draft in LSR WG. Maybe a short line explaining what degree in graph theory is may help with the document for non-native English speakers.

In my search for some level of understanding on what to understand of degree:

"In graph theory, the degree of a vertex refers to the number of edges connected to that vertex. For undirected graphs, this simply means the count of edges touching the vertex. For directed graphs, you can distinguish between the "in-degree" and the "out-degree" of a vertex: the in-degree is the number of edges coming into the vertex, and the out-degree is the number of edges going out from the vertex.

For example, in an undirected graph, if a vertex has three edges connected to it, its degree is 3. In a directed graph, if a vertex has two arrows pointing to it and one arrow pointing away, its in-degree is 2 and its out-degree is 1."

417	   If the leader chooses to include a multi-access broadcast LAN segment
418	   as part of the flooding topology, all of the links in that LAN
419	   segment should be included as well.  Once updates are flooded on the
420	   LAN, they will be received by every attached node.

The links mentioned here seem to not correspond to the physical links but instead to the graph links.
I assume a link here is from each unique router on the LAN segment to the DR/DIS and from the DR/DIS to each unique router connected on the LAN segment?
Or is the term link referencing to something else?

422	4.4.  Topologies on Complete Bipartite Graphs

I agree with the comments from others that a short drawing would make the topology descriptions easier to comprehend

493	   If two nodes are adjacent on the flooding topology and there are a
494	   set of parallel links between them, then any given update MUST be
495	   flooded over a single one of those links.  The selection of the

small proposed re-edit for reading clarity:

"If two nodes are adjacent in the flooding topology and there is a set of parallel links between them, then any given update MUST be flooded over only one of those links"
 
513	   these edges is optional.  Note that this may result in the
514	   possibility of "hidden nodes" which are part of the flooding topology

I have sometimes seen the term "stealth" used for hidden nodes or devices

525	   Other encodings are certainly possible.  We have attempted to make a
526	   useful trade-off between simplicity, generality, and space.

Not sure who is 'we'? i have seen mostly in IETF style suggestions avoiding it in favor of more 
direct or passive constructions to maintain formal tone and objectivity.

662	5.1.3.  IS-IS Area Node IDs TLV

Not sure it is clear from the text paragraph where this TLV is inserted in the hierarchy of TLVs.
For example, for the "IS-IS Dynamic Flooding Sub-TLV" it is explicitly mentioned.
(TLVs in section 5.1.4/5.1.5/5.1.6 do not have a explicit indication of place in the TLV hierarchy either)

693	      Length: 3 + ((System ID Length + 1) * (number of node IDs))

Should it be mentioned that the unit is octets? if ever a yang is created it will be in there documented anyway
why does length start with '3'? I am missing a calculation logic

826	   In support of advertising which edges are currently enabled in the
827	   flooding topology, an implementation MAY indicate that a link is part
828	   of the flooding topology by advertising a bit-value in the Link
829	   Attributes sub-TLV defined by [RFC5029].

The register is standards action. and that seems according RFC8126 section 4 (https://www.rfc-editor.org/rfc/rfc8126.html#section-4) to require a standards track document or a BCP. This document is target to be experimental.

4.9.  Standards Action

   For the Standards Action policy, values are assigned only through
   Standards Track or Best Current Practice RFCs in the IETF Stream.

1978	   IANA is requested to set up a registry called "IGP Algorithm Type For
1979	   Computing Flooding Topology" under the existing "Interior Gateway
1980	   Protocol (IGP) Parameters" IANA registry.

Not explicit mentioned here, but which IANA a Registration Policy is implied? 
https://www.rfc-editor.org/rfc/rfc8126.html#section-4

Thank you to Reese Enghardt for the GENART review.