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

Greg Mirsky <gregimirsky@gmail.com> Mon, 24 April 2023 18:00 UTC

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From: Greg Mirsky <gregimirsky@gmail.com>
Date: Mon, 24 Apr 2023 10:59:55 -0700
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To: "Matthew Bocci (Nokia)" <matthew.bocci@nokia.com>
Cc: Ketan Talaulikar <ketant.ietf@gmail.com>, spring <spring@ietf.org>, "spring-chairs@ietf.org" <spring-chairs@ietf.org>
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Subject: Re: [spring] Pending work items on draft-ietf-spring-bfd
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Hi Ketan and Matthew,
thank you for your insights into the applicability of the S-BFD application
in Segment Routing. I would greatly appreciate it if you could help me
understand the relationship between the general statement "S-BFD is used to
monitor SR Policy" and its application if SR-based SFC as described in
draft-ietf-spring-nsh-sr
<https://datatracker.ietf.org/doc/draft-ietf-spring-nsh-sr/>. I interpret
the statement "S-BFD is used to monitor an SR Policy" as applicable to all
scenarios with all behaviors. If that is the case, how would the SR part of
the encapsulation of the S-BFD Control message look in SR-based SFC? Would
it be identical to the encapsulation of a data packet that includes NSH?
Thank you for your help.

Regards,
Greg

On Fri, Mar 31, 2023 at 10:23 AM Matthew Bocci (Nokia) <
matthew.bocci@nokia.com> wrote:

> 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
>
> ------------------------------
> *From:* spring <spring-bounces@ietf.org> on behalf of Greg Mirsky <
> gregimirsky@gmail.com>
> *Sent:* Wednesday, March 29, 2023 3:19:47 AM
> *To:* Ketan Talaulikar <ketant.ietf@gmail.com>
> *Cc:* spring <spring@ietf.org>; spring-chairs@ietf.org <
> spring-chairs@ietf.org>
> *Subject:* Re: [spring] Pending work items on draft-ietf-spring-bfd
>
>
> CAUTION: This is an external email. Please be very careful when clicking
> links or opening attachments. See http://nok.it/ext for additional
> information.
>
>
> 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 <ketant.ietf@gmail.com>
> 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 <gregimirsky@gmail.com> 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: <internet-drafts@ietf.org>
> Date: Mon, Mar 27, 2023 at 6:00 PM
> Subject: New Version Notification for draft-ietf-spring-bfd-06.txt
> To: Mach Chen (Guoyi) <mach.chen@huawei.com>, Greg Mirsky <
> gregimirsky@gmail.com>, Ilya Varlashkin <imv@google.com>, Jeff Tantsura <
> jefftant.ietf@gmail.com>, Jiang Wenying <jiangwenying@chinamobile.com>
>
>
>
> 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.
>
>
>
>
> The IETF Secretariat
>
>
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