Hi Tom,

Since you responded to both mails (from me and from Dhruv) together, I'll 
respond here.

Please see inline <S2>.

Regards,
Samuel

-----Original Message-----
From: tom petch <ie...@btconnect.com> 
Sent: Thursday, January 11, 2024 1:25 PM
To: Dhruv Dhody <dhruv.i...@gmail.com>
Cc: Samuel Sidor (ssidor) <ssi...@cisco.com>; pce@ietf.org
Subject: Re: [Pce] Any missed comments for draft-ietf-pce-sid-algo

inline <tp2>

________________________________________
From: Dhruv Dhody <dhruv.i...@gmail.com>
Sent: 10 January 2024 13:06

Hi Tom, WG,

Speaking as a WG member...

On Wed, Jan 10, 2024 at 4:30 PM tom petch 
<ie...@btconnect.com<mailto:ie...@btconnect.com>> wrote:
Sent: 10 January 2024 10:18

Hi PCE WG,

I would like to ask for WG LC for draft-ietf-pce-sid-algo on behalf of authors. 
Are there any remaining issues/comments/questions which I (or co-authors) 
missed and which are not handled yet?

URL: https://datatracker.ietf.org/doc/draft-ietf-pce-sid-algo/

<tp>
Well new to the PCE list may be I fear but I have a basic problem about 
'algorithm'.

You reference RFC8665 and RFC 8667.  In those it is always SR-Algorithm so I 
think that that should be the spelling here.


Dhruv: The container is SR-ERO and SRv6-ERO where the field "Algorithm" is 
being added. To me it is clear it is an SR-Algorithm. You will find the similar 
usage in other RFC i.e.the TLV is called SR-Algorithm TLV but the field inside 
is just Algorithm.

<tp2>
You miss my point. in the two RFC it is always SR-Algorithm and never SR 
Algorithm.  The I-D has 53 or so uses of SR Algorithm. I think that they all 
need changing to SR-Algorithm.  This is not grammar; this is being consistent 
in terminology across the IETF.

<S2> Ack, in my previous mail I confirmed that I can change it. I'm for 
consistency here as well (and especially since it does not cost us anything 
now). 

More fundamentally,  8665 sets up an IANA registry with two values, 0 and 1, 
which tells me that 8665 is out of date as soon as it is published and that all 
references should be  to IANA and not the RFC.  The update policy is Standards 
Action.  ADs regard additions to IANA registries as not updating the RFC 
creating the registry so reading 8665 will not tell you that it is out of date 
unless you read between the lines of the IANA Considerations and go see what is 
current.


Dhruv: It is usual for one to reference the RFC that created the registry, it 
is evident there will be future RFCs or documents that add more codepoints; the 
reference to the original RFC that created the registry is still valid. I don't 
recall anyone asking to explicitly reference the registry. That said, there is 
no harm in adding an additional reference to IANA.

<tp2>
Well I have been around long enough to see multiple IETF WG get into a tangle 
over IANA registries and then spend a lot of effort trying to clear the 
confusion.  When this I-D is specifying the values that must appear in a 
protocol field from an IANA registry, e.g. s.3.2, then the reference  must be 
to the IANA registry.  The RFC setting up the registry will likeleyo contain 
additional information about the values and their uses so the RFC should be 
referenced, sometimes even after the RFC is obsoleted, but not for the protocol 
field; that way brings trouble in the future from those who are not thorough 
enough to spot the use of a IANA registry and understand the implications 
therof.

<S2> In my previous response, I confirmed that I should add explicit reference 
to registry itself. I originally added reference to RFC8665/RFC8667 as those 
are describing purpose and details of SR-Algorithm, but I agree that finally 
any value from IANA registry can be used in PCEP as well, so we need to 
reference registry itself as well. 

It gets more problematic.  The IANA registry was updated by RFC9350 which keeps 
the same update criteria  but splits the range into two 0-127 and 128-255, the 
latter being flexible.

s.4.2.1 talks of Flexible Algorithm with a Normative reference to RFC9350 which 
begs the question as to the relationship between SR Algorithm and Flexible 
Algorithm when used in this document. Either/or, Synonyms?

Here and  now it may all be obvious but in years to come with multiple 
algorithms in use it will likely be unclear what you are referencing in s.3.2, 
s.3.3, s.3.4; is it the range 0-127 or 0-255 or 128-255 or...?


Dhruv: It is 0-255! Authors can make that explicit in the I-D.
<tp2>
Well yes and no.  I think but am not sure that Flexible Algorithm is values 
128-255 and s.3.4 supports that view, at least  implicitly.  I think that 4.2.1 
should be explicit e.g.
'When the value of fthe  Algorithm is in the range 128-255, i.e. Flexible 
Algorithm, ...'

Tom Petch
</tp2>
<S2> This document is by default talking about complete SR-Algorithm range. 
Only exception is s.4.2.1, which is specified to 128-255 and that is already 
clarified in s.3.4 (which is explicitly excluding 0-127 and explicitly pointing 
to s.4.2.1). I can still add explicit statement to the beginning of s.4.2.1 to 
limit scope to Flexible Algorithms.

To summarize - changes to be done to this draft:
        - replace "SR algorithm" with "SR-Algorithm"
        - add explicit reference to IANA registry on top of existing references 
to RFCs, which are defining values in that registry
        - add explicit statement to beginning of s.4.2.1 to clarify that it is 
applicable to 128-255 range only

Would that work for you?

</S2>

Thanks!
Dhruv


Tom Petch



Thanks a lot,
Samuel

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