Re: [Idr] BGP-LS and the like ...

[Eric C Rosen <[e-mail]>]

On 6/25/2018 11:17 AM, Susan Hares wrote:
>
> [Sue]:
>
> 1^st - If you provide a “hint”, then we get into a recursive problem 
> of the hint accelerating the solution the controller provides.  See 
> the earliest ARPANET where the hints of performance causes the 
> solution to grow dramatically without bounds in an algorithm.   If it 
> is suggesting how many local labels it is allocating, it is suggesting 
> something that may impact.
>

I don't understand this objection.    Typically, when a node receives a 
SAFI-4 update, and has to propagate that update on an EBGP session, it 
changes the label value and the next hop value before propagation.  The 
"hint" tells you what to change the label value to.  Without the hint, 
you make a local choice of what to change the label value to.  There is 
nothing here that is "growing without bounds" or causing a "recursive" 
problem.

Also, I don't understand what ARPANET phenomenon is being referenced ;-)

> 2^nd - If you use a transitive BGP Prefix SID Attribute, then you are 
> not within a single AS. You cannot use the AS boundary to guarantee 
> the administrative SR domain.   If the configured SR Domain ID is 
> someplace (configuration, etc), then how do we check it to determine 
> SR domain boundares.
>

The problem here is that the notion of "AS boundary" as "administrative 
boundary" has long been obsolete.  The attribute under discussion is 
just one of a whole set of attributes that could benefit from a general 
"attribute scoping" solution, assuming someone could figure out a 
solution that is general enough to make sense and not too costly to 
deploy.  You can't expect this particular draft to address that problem.