[Idr] Benjamin Kaduk's No Objection on draft-ietf-idr-bgp-optimal-route-reflection-25: (with COMMENT)

Benjamin Kaduk via Datatracker <noreply@ietf.org> Wed, 16 June 2021 16:19 UTC

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Subject: [Idr] Benjamin Kaduk's No Objection on draft-ietf-idr-bgp-optimal-route-reflection-25: (with COMMENT)
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Benjamin Kaduk has entered the following ballot position for
draft-ietf-idr-bgp-optimal-route-reflection-25: No Objection

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COMMENT:
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Thank you for this document; it gives a clear explanation of what is to
be done and why, and I basically only have nit-level comments, with the
exception of the first remark.

Section 4

   This solution can be deployed in traditional hop-by-hop forwarding
   networks as well as in end-to-end tunneled environments.  In networks
   where there are multiple route reflectors and hop-by-hop forwarding
   without encapsulation, such optimizations SHOULD be consistently
   enabled on all route reflectors.  Otherwise, clients may receive an
   inconsistent view of the network, in turn leading to intra-domain
   forwarding loops.

The scope of "forwarding loops" as a potential problem makes me wonder
if the "SHOULD"-level requirement for this avoidance mechanism is the
right choice.

Section 5

Thank you for accepting the wording suggestion from Roman; it's a good
improvement.

I might consider reiterating that there are risks if multiple route
reflectors are present but using different policy/procedures, though the
earlier discussion may suffice.

Section 9.2

Whether RFC 7911 should be normative or informative seems potentially
subject to debate, if deployment of add-path is required in order for
correct operation of optimal route reflectors.

NITS

                                                    This ability enables
   the route reflector to send to a given set of clients routes with
   shortest distance to the next hops from the position of the selected
   IGP location.  [...]

This feels a bit like a garden-path sentence that makes the reader
backtrack to fix their parse tree; commas around "to a given set of
clients" might help but a more substantive restructuring might be
preferred.

                  This provides for freedom of route reflector physical
   location, and allows transient or permanent migration of this network
   control plane function to an arbitrary location.

Pedantically, such a migration seems like it would always have been
possible, just with a potentially significant impact on performance and
route quality; I'd suggest appending a phrase such as "with negligible
impact on performance".

   The choice of specific granularity (route reflector, set of clients,
   or client) is configured by the network operator.  An implementation
   is considered compliant with this document if it supports at least
   one listed grouping of IGP location.

It's not entirely clear to me how a "listed grouping of IGP location"
maps to the previous text.

Section 3.2

   If the required routing optimization is limited to the IGP cost to
   the BGP Next-Hop, only step e) and below as defined [RFC4271] section
   9.1.2.2, needs to be run multiple times.

I think maybe s/and below/and subsequent steps/, and s/as defined/as
defined in/.

Section 4

   route reflectors.  More specifically, the choice of BGP path factors
   in either the IGP cost between the client and the NEXT_HOP (rather

I suggest s/factors in/takes into account/, since "factors in" is
something of a colloquialism.

   Modifying the IGP location of BGP ORR does not interfere with
   policies enforced before IGP tie-breaking (step e) in the BGP
   Decision Process Route.

I think "step e" has to be scoped to §9.1.2.2 of RFC 4271.

                                                          Similarly, if
   an IGP location is selected for the whole routing instance, the
   lowest precision is achieved, but the performance impact is minimal
   (both should be equal to the [RFC4456] ones).  [...]

The phrasing in the parenthetical seems surpising to me -- what does
"both" refer to?  I can only see the one "performance of the
single-IGP-location-for-the-whole-routing-instance" situation, which of
course should have equivalent performance to the stock RFC 4456 case.

Section 5

   This extension provides a new metric value using additional
   information for computing routes for BGP router reflectors.  While

s/router/route/