# Gunter Van de Velde, RTG AD, comments for draft-ietf-lsr-ospf-admin-tags-22

# The referenced line numbers are derived from the idnits tool:
https://author-tools.ietf.org/api/idnits?url=https://www.ietf.org/archive/id/draft-ietf-lsr-ospf-admin-tags-22.txt

# Many thanks for this write-up. The document is well written and was a 
pleasure to read.

# idnits tool comes up clean

# Many thanks to Christian Hopps for the Shepherd write-up, Russ White for the 
RTGDIR review and Qiufang Ma for the YANGDOCTORS review

#DETAILED COMMENTS
#==================

139           Type     A 16-bit field set to TBD.

GV> From readability, maybe call out that there is a:
TBD1: "OSPF Extended Prefix TLV Sub-TLV" Registry
TBD2: "OSPFv3 Extended-LSA Sub-TLV" Registry
TBD3: "OSPFv3 SRv6 Locator LSA Sub-TLVs" Registry

210        action.  Whether or not tag A precedes or succeeds tag B SHOULD NOT
211        change the meaning of the tag set.  The number of tags supported MAY

GV> the "tag set" wording may be unclear and confusing. Is it the "tag that is 
set" or the "set of tags".
What about:

"
Regardless of whether tag A precedes or follows tag B, the meaning of the tag 
SHOULD NOT be affected.
"

211        change the meaning of the tag set.  The number of tags supported MAY
212        limit the number of tags that are propagated.  When propagating

GV> I suspect that this is referencing to the number of tags on the ABR and/or 
the router originating the prefix with its associated tags?
Is this something that can be further accurately explained? What about:

"
The number of supported tags on the router originating the prefix or on an ABR 
MAY limit the number of tags that are ultimately propagated.
"

217        For configured area ranges, NSSA ranges, and configured aggregation
218        of redistributed routes, tags from component routes SHOULD NOT be
219        propagated to the summary.  Implementations SHOULD provide a
220        mechanism to configure multiple tags for area ranges, NSSA ranges,
221        and redistributed route summaries.

GV> Why is this a SHOULD NOT instead of a MUST NOT? What breaks or causes 
issues if tags would be propagated to a summary?

226        these LSAs will all have different tags.  In this situation, the OSPF
227        router MUST associate the tags from one of the LSAs contributing a
228        path and, if the implementation supports multiple tags, MAY associate
229        tags from multiple contributing LSAs up to the maximum number of tags
230        supported.  It is RECOMMENDED that tags from LSAs are added to the

GV> It displays "multiple tags supported", however it is unclear by which 
router this observation must be applied

247        However, the default behavior SHOULD be to advertise or propagate the
248        lesser number of all the tags associated with the prefix or the
249        maximum number of tags supported by the implementation.

GV> I managed to get confused with what the "lesser number" exactly means? is 
this the number of tags according to the policy? 

GV> Would it be allowed for ABRs to impose additional tags upon prefixes for 
management reasons? Or can only the router that originates a specific prefix 
set one or multiple tags

251        Both the support of this specification and the number of tags
252        supported by OSPF routers within an OSPF routing domain will limit
253        the usefulness and deployment of applications utilizing tags.

GV> Is it expected that all routers in the routing domain support the same 
number of tags?

742     9.  IANA Considerations
743
744        The following values should be allocated from the "OSPF Extended
745        Prefix TLV Sub-TLV" Registry [RFC7684]:
746
747        *  TBD - Administrative Tag Sub-TLV
748
749        The following values should be allocated from the "OSPFv3 Extended-
750        LSA Sub-TLV" Registry [RFC8362]:
751
752        *  TBD - Administrative Tag Sub-TLV
753
754        The following values should be allocated from the "OSPFv3 SRv6
755        Locator LSA Sub-TLVs" Registry [RFC9513]:
756
757        *  TBD - Administrative Tag Sub-TLV

GV> maybe call out that there are three TBDs (TBD1, TBD2 and TBD3) as seen from 
section 2

Brgds,
G/


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