Hi Bruno

>From an operators perspective your creative  idea of using the existing SR
machinery using the node SID to advertise the Area SID in the Proxy LSP is
very attractive to be able to support the feature immediately without
requiring a feature upgrade to support.

This idea really helps the area proxy concept  come to fruition without
impacting operations.



On Wed, Aug 5, 2020 at 4:08 PM Tony Li <tony1ath...@gmail.com> wrote:

> Les,
> *a)Advertise the “Area Prefix” in the Area Proxy TLV – much as we do a
> router-id today in the Router-ID TLV.*
> This would make the Area Prefix mandatory for Area Proxy, which is not
> desired.  We would prefer it to remain optional and thus part of the Area
> SID sub-TLV.
> *b)The remaining info (reachability and SID) can then be provided using
> existing Prefix Reachability advertisements – no need for new sub-TLV for
> “Area SID”. This eliminates any potential issues if the SID advertised by
> “Area SID sub-TLV” were to differ from the SID advertised in Prefix
> Reachability for the same prefix.*
> As we discussed privately, we view this as a non-issue.  The Area Leader
> is the one advertising both the Area SID sub-TLV and the Proxy LSP. If
> there’s a coding error, there’s a coding error. There is a single source of
> truth (the Area Leader’s config) and we cannot protect against every
> possible coding error.  Reconciling the prefix with a separate
> advertisement has a non-trivial chance of being broken too, and IMHO, much
> larger.
>  *There then remains the question as to whether the “Area Prefix” is
> anycast or unicast i.e., is it common to all IERs or is it unique to
> whomever gets elected Area Leader?*
> Does it matter? We have no clear semantics for this prefix. A difference
> that makes no difference is no difference.
> Tony
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*Gyan Mishra*

*Network Solutions A**rchitect *

*M 301 502-134713101 Columbia Pike *Silver Spring, MD
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