Mohamed Boucadair has entered the following ballot position for
draft-ietf-lsr-anycast-flag-09: No Objection

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COMMENT:
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Hi Ran, Detao, Peter, Ketan, and Changwang,

Thank you for the effort put into this specification, which is about mirroring
a functionality already specified for IS-IS and OSPFv3.

Thanks to Juergen for the OPSDIR review and Ran for engaging. Some of the
replies in the thread are better if echoed in the document (e.g., backward
compatibility mention).

I would ballot Yes if two first points below were addressed.

I have two main points and a set of more low-level comments:

# Summarization

CURRENT:
   The AC-flag MUST be preserved when re-advertising the prefix across
   areas.

Wouldn’t that be lost if the prefix is covered a summarized adv by an ABR?

Maybe tweak this as?

NEW:
    The AC-flag MUST be preserved when the
    OSPFv2 Extended Prefix Opaque LSA is propagated between areas.

# Operational Considerations

## Consistent configuration

In addition to the backward compatibility mentioned above, I would add a brief
discussion that basically say that anycast prefixes should be consistently
managed through the network. Stale configuration of a prefix tagged as anycast
may have implications as that value will take precedence over other same prefix
announcement with AC-flag set to 0.

## Anomalies

You may also add a point retrieval of a router configuration having N-flag and
AC-flag set to 1 for a given prefix should be used as an indication of
configuration anomaly.

Alos, consider adding a point that receipt of adv with both N-flag and AC-flag
set to 1 can be used as an indication of configuration anomaly. This can be
used by a network controller.

BTW, how such function is supposed to be done using the YANG-based interface?
Is retrieval of prefix flags from peers covered by the base YANG OSPF module?
If so, please add a mention of the data nodes used for that purpose.

## Please find below some additional comments, fwiw:

## Identifier

CURRENT:
   It is useful for other
   routers to know that the advertisement is for an anycast identifier.

I appreciate this text is grabbed from SR OSPF/IS-IS extension, but I would
s/anycast identifier/ anycast prefix

## Mention the YANG augmentation in the abstract

OLD:
   This document defines a new flag in the OSPFv2 Extended Prefix TLV
   Flags to advertise the anycast property.

NEW:
   This document defines a new flag in the OSPFv2 Extended Prefix TLV
   Flags to advertise the anycast property. The document also specifies
   a companion YANG module for managing this function.

You may consider a mention in the introduction as well.

## set/clear

You may add a mention to say that “set” meant “set to 1” and “clear” means “set
to 0”.

## Curiosity

CURRENT:
  When a prefix is configured as anycast, the AC-flag MUST be set

Just out of curiosity, why the WG went for a distinct behavior for the IS-IS
part as RFC9352 has: “When the prefix/SRv6 Locator is configured as anycast,
the A-flag SHOULD be set”

## Manage vs configure

OLD:
   This section defines a YANG data model that can be used to configure
   and manage the usage of OSPFv2 Anycast Property as defined in this

NEW:
   This section defines a YANG data model that can be used to manage
   the usage of OSPFv2 Anycast Property as defined in this

“configure” is one of the management (FCAPS) function

## nit

OLD: The following show the tree diagram of the module:

NEW: The following shows the tree diagram of the module:

## No need to have the NMDA mention in the module (*)

Consider deleting:

CURRENT:
        This YANG module conforms to the Network Management
        Datastore Architecture (NMDA) as described in RFC 8342.

## The module is not only about configuration, but also retrieval (*)

(1)

OLD:
       "This YANG module adds the support of configuring an OSPFv2
        prefix as anycast.

NEW:
       "This YANG module adds the support of managing an OSPFv2
        prefix as anycast.

(2) Delete:

OLD:
/* Configuration */

(3)

OLD: "This augments the OSPFv2 interface configuration.";

NEW: "This augments the OSPFv2 interface.";

(4)

OLD: "This augments OSPFv2 interface configuration with anycast

NEW: "This augments OSPFv2 interface with anycast

## Update to follow the IETF template + no need to have a reference clause

OLD:
        This version of this YANG module is part of RFC XXXX;
        see the RFC itself for full legal notices.";
     reference
       "RFC XXXX";

NEW:
        All revisions of IETF and IANA published modules can be found
        at the YANG Parameters registry group
        (https://www.iana.org/assignments/yang-parameters).

        This version of this YANG module is part of RFC XXXX; see
        the RFC itself for full legal notices.";

## This is an identity, not a boolean

“when set” does not parse here.

OLD:
       description
         "Anycast flag.  When set, it indicates that the prefix
          is configured as anycast.";

NEW:
       description
         "Indicates that the prefix is configured as anycast.";

## Data node description

OLD:
       leaf anycast-flag {
         type boolean;
         default "false";
         description
           "Sets the prefix as an anycast address.";

NEW:
       leaf anycast-flag {
         type boolean;
         default "false";
         description
            “Indicates that the prefix is an anycast address, if set to 1.
             It indicates a node-specific prefix if set to 0.";

## Please update Section 6 to follow the template at
https://datatracker.ietf.org/doc/html/draft-ietf-netmod-rfc8407bis-28#name-security-considerations-sect

## These are not normative

### Move RFC6241 and RFC8040 to be listed as Informative

### I don’t think RFC9085 is normative, but I leave it to you to double check.

Cheers,
Med



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