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From: Robert Raszuk <robert@raszuk.net>
Date: Mon, 7 Jul 2025 22:59:18 +0200
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To: sekrier@cisco.com, "Jakub Horn (jakuhorn)" <jakuhorn@cisco.com>,
 mihai.ciurea@swisscom.com
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Hi,

Allow me to observe before even further commenting on the draft that
motivation for the IGP UPA work was based on the trigger of node down event
(planned or unplanned) in one non backbone areas.

With that the analogy in the BGP world is not to advertise all atomic
prefixes which may have become unreachable, but instead quickly propagate
information about the next hop down event which is by design shared across
all such prefixes/locators.

I along with few collegues in 2005 we wrote a draft -
https://www.ietf.org/archive/id/draft-raszuk-aggr-withdraw-00.txt

At that time there was no sufficient interest in signalling such events in
BGP.

If you think that times have changed I recommend you take a look at this
draft and possibly respin it or reuse it.

Thx a lot,
Robert

PS. After a quick read I do have a number of comments on the text in the
draft however before we go down that path let's consider the alternative
approach.


---------- Forwarded message ---------
From: <internet-drafts@ietf.org>
Date: Mon, Jul 7, 2025 at 7:41=E2=80=AFPM
Subject: I-D Action: draft-krierhorn-idr-upa-00.txt
To: <i-d-announce@ietf.org>


Internet-Draft draft-krierhorn-idr-upa-00.txt is now available.

   Title:   SRv6 BGP Unreachable Prefix Announcement (UPA)
   Authors: Serge Krier
            Jakub Horn
            Mihai Ciurea
   Name:    draft-krierhorn-idr-upa-00.txt
   Pages:   8
   Dates:   2025-07-07

Abstract:

   Summarization is often used in multi-domain networks to improve
   network efficiency and scalability.  With summarization in place,
   there is a need to signal loss of reachability to an individual
   prefix covered by the summary.  This enables fast convergence by
   steering traffic away from the node which owns the prefix and is no
   longer reachable.

   This mechanism, referred to as Unreachable Prefix Announcement (UPA),
   has been specified for IGPs.  This document specifies an and
   equivalent BGP mechanism for multi-AS networks where BGP is used to
   carry summary routes.

The IETF datatracker status page for this Internet-Draft is:
https://datatracker.ietf.org/doc/draft-krierhorn-idr-upa/

There is also an HTML version available at:
https://www.ietf.org/archive/id/draft-krierhorn-idr-upa-00.html

Internet-Drafts are also available by rsync at:
rsync.ietf.org::internet-drafts


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<div dir=3D"ltr"><div>Hi,</div><div><br></div><div>Allow me to observe befo=
re even further commenting on the draft that motivation for the IGP UPA wor=
k was based on the trigger of node down event (planned or unplanned) in one=
 non backbone areas.=C2=A0</div><div><br></div><div>With that the analogy i=
n the BGP world is not to advertise all atomic prefixes which may have beco=
me unreachable, but instead quickly propagate information about the next ho=
p down event which is by design shared across all such prefixes/locators.=
=C2=A0</div><div><br></div><div>I along with few collegues in 2005 we wrote=
 a draft -=C2=A0<a href=3D"https://www.ietf.org/archive/id/draft-raszuk-agg=
r-withdraw-00.txt">https://www.ietf.org/archive/id/draft-raszuk-aggr-withdr=
aw-00.txt</a></div><div><br></div><div>At that time there was no sufficient=
 interest in signalling such events in BGP.=C2=A0</div><div><br></div><div>=
If you think that times have changed I recommend you take a look at this dr=
aft and possibly respin it or reuse it.=C2=A0</div><div><br></div><div>Thx =
a lot,</div><div>Robert</div><div><br></div><div>PS. After a quick read I d=
o have a number of comments on the text in the draft however before we go d=
own that path let&#39;s consider the alternative approach.=C2=A0</div><div>=
<br></div><br><div class=3D"gmail_quote gmail_quote_container"><div dir=3D"=
ltr" class=3D"gmail_attr">---------- Forwarded message ---------<br>From: <=
span dir=3D"auto">&lt;<a href=3D"mailto:internet-drafts@ietf.org">internet-=
drafts@ietf.org</a>&gt;</span><br>Date: Mon, Jul 7, 2025 at 7:41=E2=80=AFPM=
<br>Subject: I-D Action: draft-krierhorn-idr-upa-00.txt<br>To:  &lt;<a href=
=3D"mailto:i-d-announce@ietf.org">i-d-announce@ietf.org</a>&gt;<br></div><b=
r><br>Internet-Draft draft-krierhorn-idr-upa-00.txt is now available.<br>
<br>
=C2=A0 =C2=A0Title:=C2=A0 =C2=A0SRv6 BGP Unreachable Prefix Announcement (U=
PA)<br>
=C2=A0 =C2=A0Authors: Serge Krier<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Jakub Horn<br>
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 Mihai Ciurea<br>
=C2=A0 =C2=A0Name:=C2=A0 =C2=A0 draft-krierhorn-idr-upa-00.txt<br>
=C2=A0 =C2=A0Pages:=C2=A0 =C2=A08<br>
=C2=A0 =C2=A0Dates:=C2=A0 =C2=A02025-07-07<br>
<br>
Abstract:<br>
<br>
=C2=A0 =C2=A0Summarization is often used in multi-domain networks to improv=
e<br>
=C2=A0 =C2=A0network efficiency and scalability.=C2=A0 With summarization i=
n place,<br>
=C2=A0 =C2=A0there is a need to signal loss of reachability to an individua=
l<br>
=C2=A0 =C2=A0prefix covered by the summary.=C2=A0 This enables fast converg=
ence by<br>
=C2=A0 =C2=A0steering traffic away from the node which owns the prefix and =
is no<br>
=C2=A0 =C2=A0longer reachable.<br>
<br>
=C2=A0 =C2=A0This mechanism, referred to as Unreachable Prefix Announcement=
 (UPA),<br>
=C2=A0 =C2=A0has been specified for IGPs.=C2=A0 This document specifies an =
and<br>
=C2=A0 =C2=A0equivalent BGP mechanism for multi-AS networks where BGP is us=
ed to<br>
=C2=A0 =C2=A0carry summary routes.<br>
<br>
The IETF datatracker status page for this Internet-Draft is:<br>
<a href=3D"https://datatracker.ietf.org/doc/draft-krierhorn-idr-upa/" rel=
=3D"noreferrer" target=3D"_blank">https://datatracker.ietf.org/doc/draft-kr=
ierhorn-idr-upa/</a><br>
<br>
There is also an HTML version available at:<br>
<a href=3D"https://www.ietf.org/archive/id/draft-krierhorn-idr-upa-00.html"=
 rel=3D"noreferrer" target=3D"_blank">https://www.ietf.org/archive/id/draft=
-krierhorn-idr-upa-00.html</a><br>
<br>
Internet-Drafts are also available by rsync at:<br>
rsync.ietf.org::internet-drafts<br>
<br>
<br>
_______________________________________________<br>
I-D-Announce mailing list -- <a href=3D"mailto:i-d-announce@ietf.org" targe=
t=3D"_blank">i-d-announce@ietf.org</a><br>
To unsubscribe send an email to <a href=3D"mailto:i-d-announce-leave@ietf.o=
rg" target=3D"_blank">i-d-announce-leave@ietf.org</a><br>
</div></div>

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