Re: [Idr] Opsdir early review of draft-ietf-idr-bgp-optimal-route-reflection-21

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Dan,

Thanks for your review and comments.
Please see inline [Bruno]

> From: Dan Romascanu via Datatracker [mailto:[e-mail]]
> Sent: Thursday, December 3, 2020 11:43 AM
> 
> Reviewer: Dan Romascanu
> Review result: Has Issues
> 
> This document defines an extension to BGP route reflectors by which BGP
> route
> selection is modified in order to choose the best path for their clients
> standpoint, rather than from the route reflectors standpoint. The
> Introduction
> includes text that describes in what situations these extensions are
> applicable.
> 
> >From the operators perspective, Section 4 and Section 6 includes important
> recommendations for SP operators, as well as deployment considerations.
> 
> The document is Almost Ready from an OPS perspective. I would suggest
> however
> to clarify the following two issues before approval:
> 
> 1. In Section 3:
> 
> > Both modifications rely upon all route reflectors learning all paths
>    that are eligible for consideration.  In order to satisfy this
>    requirement, path diversity enhancing mechanisms such as add-path may
>    need to be deployed between route reflectors.
> 
> What are the consequences of this condition not being met? Are there any
> requirements or recommendations for operators in deployment? Some
> clarification
> text would be useful, did I miss something?

[Bruno] Good point.

I'd propose the following change:
OLD:
<t>Both modifications rely upon all route reflectors learning all paths 
that are eligible for consideration. In order to 
satisfy this requirement, path diversity enhancing mechanisms such as 
add-path may need to be deployed between route 
reflectors.</t>

NEW:
<t>For both modifications, the achievement of optimal routing relies upon all route reflectors learning all paths 
that are eligible for consideration. In order to 
satisfy this requirement, path diversity enhancing mechanisms such as 
BGP add-path <xref target="RFC7911" /> may need to be deployed between route 
reflectors.</t>


Do you think that the consequences of not doing so (i.e. not achieving optimal routing) are clear enough, or should we add another sentence?
As this text if for network operator more than implementers, I would propose to move it to section " 6.  Advantages and Deployment Considerations". More specifically after the first paragraph. I which case I would remove " For both modifications," which act as a liaison with previous text in section 3.

> 2. In Section 3.1:
> 
> > In addition to the change specified in [RFC4456] section 9, the BGP
>    Decision Process Tie Breaking rules ([RFC4271] Sect.  9.1.2.2) are
>    modified as follows.
> 
> Should not the document UPDATE RFC 4271 (when approved)?
 
[Bruno] I don't believe so.
- In the sense that people implementing 4271 but not implementing this document do not need to be aware of this document.
- This document is primarily an extension of BGP Route Reflector [1].  BGP Route Reflector did change the decision process but  did not update 4271.

That been said, I leave this to the AD/IESG.

[1] https://tools.ietf.org/html/rfc4456


Somewhat related I moved RFC 4456 (BGP RR) from Informative to Normative Reference.

Thanks,

--Bruno



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