Re: [Lsr] I-D Action: draft-ietf-lsr-isis-srv6-extensions-10.txt

[Joel Halpern <[e-mail]>]

The announcement prompted me to look again and think about an 
interaction between this and the network programming draft.  To be 
clear, I am NOT objecting to either this or the network programming 
draft.  I am just wondering what I am missing.

The NP draft, and the advertisement mechanism allows a router to 
advertise the number of bits for the ARG portion of a SID.

Q1: The point presumably is to avoid needing to advertise each of the 
individual values?

An example of this is, I think, and ARG for the table selection where 
the ARG is the table number for the packet to be looked up in?

Q2: If so, how does the head end know what table number corresponds to 
what meaning?    If this requires a separate advertisement there seems 
to be no savings.  if this requires out-of-band knowledge then we seem 
to have lost the benefit of advertising all of this in the routing protocol.

I suspect I am simply missing a piece.  can someone explain please?

Thank you,
Joel

On 9/23/2020 4:40 PM, [e-mail] wrote:
> 
> A New Internet-Draft is available from the on-line Internet-Drafts directories.
> This draft is a work item of the Link State Routing WG of the IETF.
> 
>          Title           : IS-IS Extension to Support Segment Routing over IPv6 Dataplane
>          Authors         : Peter Psenak
>                            Clarence Filsfils
>                            Ahmed Bashandy
>                            Bruno Decraene
>                            Zhibo Hu
> 	Filename        : draft-ietf-lsr-isis-srv6-extensions-10.txt
> 	Pages           : 25
> 	Date            : 2020-09-23
> 
> Abstract:
>     Segment Routing (SR) allows for a flexible definition of end-to-end
>     paths by encoding paths as sequences of topological sub-paths, called
>     "segments".  Segment routing architecture can be implemented over an
>     MPLS data plane as well as an IPv6 data plane.  This draft describes
>     the IS-IS extensions required to support Segment Routing over an IPv6
>     data plane.
> 
>