Re: [spring] Pending work items on draft-ietf-spring-bfd

["Matthew Bocci (Nokia)" <[e-mail]>]

Hi Greg

I see S-BFD as the most prevalent flavour of BFD for monitoring SR Policies,  avoiding the need for LSP Ping bootstrapping. Nokia has an implementation for both MPLS and SRv6 SR Policies, and I am aware of others out there.

Given the widespread implementation of S-BFD for SR Policy, it would make sense to incorporate S-BFD as a mechanism in the SPRING BFD draft.

Regards


Matthew

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From: spring <[e-mail]> on behalf of Greg Mirsky <[e-mail]>
Sent: Wednesday, March 29, 2023 3:19:47 AM
To: Ketan Talaulikar <[e-mail]>
Cc: spring <[e-mail]>; [e-mail] <[e-mail]>
Subject: Re: [spring] Pending work items on draft-ietf-spring-bfd


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Hi Ketan,
thank you for sharing your comments about the state of draft-ietf-spring-bfd. Please find my notes in-line below under the GIM>> tag.

Regards,
Greg

On Wed, Mar 29, 2023 at 11:11 AM Ketan Talaulikar <[e-mail]<mailto:[e-mail]>> wrote:
Hi Greg/Authors,

I believe this draft still needs work before it is ready for WGLC.

Specifically, it does not cover the use of S-BFD for the monitoring of SR Policies and AFAIK this is the more widely used than the mechanism specified in the draft currently (i.e. than the bootstrap via LSP Ping to setup a "normal" BFD session).
GIM>> Can you clarify how BFD or S-BFD can monitor an SR Policy? As defined in RFC 5880, the scope of BFD is:
   a protocol intended to detect faults in the
   bidirectional path between two forwarding engines, including
   interfaces, data link(s), and to the extent possible the forwarding
   engines themselves, with potentially very low latency.
At the same time, I believe that an SR policy can be monitored using LSP Ping with the corresponding Target FEC.

I am not saying that the mechanism in the draft cannot be used, but progressing this document toward publication without reflecting the other alternate mechanism that IMO is far more widely implemented and deployed will provide a somewhat misleading picture.

My request to the authors is to consider inclusion of text from https://datatracker.ietf.org/doc/draft-ali-spring-bfd-sr-policy/ in this WG document. We can discuss f2f during this week if you agree.
GIM>> Thank you for your suggestion. Let us discuss the applicability of a BFD-based mechanism in monitoring an SR policy.

I would like us to seek inputs from implementers and operators on which of these two mechanisms they prefer/use. Including this in the document would also be helpful.
GIM>> I wholeheartedly agree and welcome anyone to share their experiences of monitoring SR policies with MPLS OAM tools.

Thanks,
Ketan

On Mon, Mar 27, 2023 at 6:04 PM Greg Mirsky <[e-mail]<mailto:[e-mail]>> wrote:
Refresh and to update author's contact information.

Dear All,
the draft is stable and the authors believe it is ready for the WG LC. We appreciate the WG Chairs' consideration for starting the WG LC.

Regards,
Greg (on behalf of the authors)

---------- Forwarded message ---------
From: <[e-mail]<mailto:[e-mail]>>
Date: Mon, Mar 27, 2023 at 6:00 PM
Subject: New Version Notification for draft-ietf-spring-bfd-06.txt
To: Mach Chen (Guoyi) <[e-mail]<mailto:[e-mail]>>, Greg Mirsky <[e-mail]<mailto:[e-mail]>>, Ilya Varlashkin <[e-mail]<mailto:[e-mail]>>, Jeff Tantsura <[e-mail]<mailto:[e-mail]>>, Jiang Wenying <[e-mail]<mailto:[e-mail]>>



A new version of I-D, draft-ietf-spring-bfd-06.txt
has been successfully submitted by Greg Mirsky and posted to the
IETF repository.

Name:           draft-ietf-spring-bfd
Revision:       06
Title:          Bidirectional Forwarding Detection (BFD) in Segment Routing Networks Using MPLS Dataplane
Document date:  2023-03-27
Group:          spring
Pages:          14
URL:            https://www.ietf.org/archive/id/draft-ietf-spring-bfd-06.txt
Status:         https://datatracker.ietf.org/doc/draft-ietf-spring-bfd/
Html:           https://www.ietf.org/archive/id/draft-ietf-spring-bfd-06.html
Htmlized:       https://datatracker.ietf.org/doc/html/draft-ietf-spring-bfd
Diff:           https://author-tools.ietf.org/iddiff?url2=draft-ietf-spring-bfd-06

Abstract:
   Segment Routing (SR) architecture leverages the paradigm of source
   routing.  It can be realized in the Multiprotocol Label Switching
   (MPLS) network without any change to the data plane.  A segment is
   encoded as an MPLS label, and an ordered list of segments is encoded
   as a stack of labels.  Bidirectional Forwarding Detection (BFD) is
   expected to monitor any existing path between systems.  This document
   defines how to use Label Switched Path Ping to bootstrap a BFD
   session, control an SR Policy in the reverse direction of the SR-MPLS
   tunnel, and applicability of BFD Demand mode in the SR-MPLS domain.
   Also, the document describes the use of BFD Echo with BFD Control
   packet payload.




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