Re: [Lsr] Fwd: New Version Notification for draft-ietf-lsr-isis-area-proxy-02.txt

[[e-mail]]

Les,

From: Les Ginsberg (ginsberg) [mailto:[e-mail]]
Sent: Thursday, July 30, 2020 7:29 PM
To: DECRAENE Bruno TGI/OLN <[e-mail]>; [e-mail]; [e-mail]
Subject: RE: [Lsr] Fwd: New Version Notification for draft-ietf-lsr-isis-area-proxy-02.txt

Bruno –

One of the reasons to use the Binding TLV to advertise the Area SID was that it has been suggested that other use cases for Area SID – unrelated to Area Proxy – may come along.
Therefore tying the advertisement to an Area Proxy TLV seems not the best option if we want to allow for these other use cases (admittedly currently unknown).

Thoughts??

I have no problem with the format or the name of the IS-IS extension used to advertise the Area SID to external L2 nodes. Binding TLV works for me.
I think that the area SID is useful to external L2 nodes, including to nodes not supporting this extension. Hence the proposal to (also) advertise it in a regular Node SID. I’ll detail the use case in a subsequent email to be sent today. Writing it done will also be beneficial to me.

Thanks,
--Bruno


   Les


From: Lsr <[e-mail]<mailto:[e-mail]>> On Behalf Of [e-mail]<mailto:[e-mail]>
Sent: Thursday, July 30, 2020 9:22 AM
To: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Subject: Re: [Lsr] Fwd: New Version Notification for draft-ietf-lsr-isis-area-proxy-02.txt

Hi Tony,

Thanks for the updated draft.

“ The Area SID Sub-TLV allows the Area Leader to advertise a SID that
   represents the entirety of the Inside Area to the Outside Area.  This
   sub-TLV is learned by all of the Inside Edge Nodes who should consume
   this SID at forwarding time.”

Excellent, from my perspective.

Ø  - The Area Segment SID TLV has been replaced by extending the Binding SID TLV.


“When SR is enabled, it may be useful to advertise an Area SID which

   will direct traffic to any of the Inside Edge Routers.  The Binding/

   MT Binding TLVs described in RFC 8667 Section 2.4<https://tools.ietf.org/html/rfc8667#section-2.4> are used to

   advertise such a SID.



   The following extensions to the Binding TLV are defined in order to

   support Area SID:



      A new flag is defined:



         T-flag: The SID directs traffic to an area.  (Bit 5) »




This works.
However I may have a different deployment environment than the one you have in mind. Even if those issues may be mine, allow me to share them with you.
In many WAN networks than I’m used to, there are routers from different vendors, platforms, software, generations. Requiring all those routers to support the new Binding SID TLV T-Flag will take time. Some platform may even be end of engineering (evolutions) so would never support such new features.
In my environment, ideally, I would prefer a solution which do not require any new feature on external L2 nodes, while all existing L2 features keep working, in particular SR, SR-TE, TI-LFA, SR uloop avoidance… This would require the Proxy LSP to be not (significantly) different than the LSP of a vanilla L2 node. For SR, I think that this would require this Proxy LSP to advertise a Prefix/Node SID with the Area SID attached. One drawback is that a Node-SID is advertised with an IP address that would need to be provisioned.

Both approaches are not mutually exclusives. I’d be happy enough with an option for the Proxy LSP to advertise an Area Node SID with the Area SID attached.

Finally, there is no requirement to make me happy ;-) . The above could also be a local implementation knob not mentioned in the draft.

Thanks,
--Bruno

From: Lsr [mailto:[e-mail]] On Behalf Of [e-mail]<mailto:[e-mail]>
Sent: Sunday, July 26, 2020 3:49 AM
To: [e-mail]<mailto:[e-mail]>
Subject: [Lsr] Fwd: New Version Notification for draft-ietf-lsr-isis-area-proxy-02.txt


Hi folks,

This version of the draft reflects major changes in line with the discussions that we’ve had so far.

To wit:
- The Area Proxy TLV is now moved to be in L2 LSPs and indicates that the advertising node is an Inside Node and Area Proxy is active.
- The Area Proxy Router Capability has been removed.
- The Inside Node TLV has been removed.
- The Area Segment SID TLV has been replaced by extending the Binding SID TLV.

We know that some folks disagree with this last point, so we welcome discussion on this. We would like to reach consensus as quickly as possible.

Thanks,
Tony


Begin forwarded message:

From: [e-mail]<mailto:[e-mail]>
Subject: New Version Notification for draft-ietf-lsr-isis-area-proxy-02.txt
Date: July 25, 2020 at 6:46:05 PM PDT
To: "Vivek Ilangovan" <[e-mail]<mailto:[e-mail]>>, "Sarah Chen" <[e-mail]<mailto:[e-mail]>>, "Gyan S. Mishra" <[e-mail]<mailto:[e-mail]>>, "Gyan Mishra" <[e-mail]<mailto:[e-mail]>>, "Yunxia Chen" <[e-mail]<mailto:[e-mail]>>, "Tony Li" <[e-mail]<mailto:[e-mail]>>


A new version of I-D, draft-ietf-lsr-isis-area-proxy-02.txt
has been successfully submitted by Tony Li and posted to the
IETF repository.

Name:                     draft-ietf-lsr-isis-area-proxy
Revision:     02
Title:                        Area Proxy for IS-IS
Document date:      2020-07-25
Group:                     lsr
Pages:                      20
URL:            https://www.ietf.org/internet-drafts/draft-ietf-lsr-isis-area-proxy-02.txt
Status:         https://datatracker.ietf.org/doc/draft-ietf-lsr-isis-area-proxy/
Htmlized:       https://tools.ietf.org/html/draft-ietf-lsr-isis-area-proxy-02
Htmlized:       https://datatracker.ietf.org/doc/html/draft-ietf-lsr-isis-area-proxy
Diff:           https://www.ietf.org/rfcdiff?url2=draft-ietf-lsr-isis-area-proxy-02

Abstract:
  Link state routing protocols have hierarchical abstraction already
  built into them.  However, when lower levels are used for transit,
  they must expose their internal topologies to each other, leading to
  scale issues.

  To avoid this, this document discusses extensions to the IS-IS
  routing protocol that would allow level 1 areas to provide transit,
  yet only inject an abstraction of the level 1 topology into level 2.
  Each level 1 area is represented as a single level 2 node, thereby
  enabling greater scale.




Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org<http://tools.ietf.org>.

The IETF Secretariat


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