Re: [mpls] I-D Action: draft-ietf-mpls-bfd-directed-22.txt

[Dhruv Dhody <[e-mail]>]

Hi,

Please find some comments on the I-D -

## Minor

* Section 1

    * IP/MPLS LSP reads a bit weird; Should this be only MPLS LSP instead
of IP/MPLS?

    * Some text for experimental status should be added in terms of scope
of the experiment, what are the next steps etc.

* Section 3.1

    * LSP Ping [RFC 7110] uses the term Reply Path, is that usage different
from Reverse Path in this I-D? It might also be a good idea to talk about
RFC 7110 in the introduction. BTW is there any relationship between the
two?  (I later saw you have some text in Section 5 but it lacks any context)

    * For the Target FEC Stack sub-TLV we need references. Is the use of
non-multicast clear for the reader, do we need to be more specific? Looking
at the registry, is this the correct list ? Not all of them use the term
multicast!

        * RSVP P2MP IPv4 Session

        * RSVP P2MP IPv6 Session

        * Multicast P2MP LDP FEC Stack

        * Multicast MP2MP LDP FEC Stack

        * P2MP Pseudowire sub-TLV

        * P2MP Policy MPLS Candidate Path

    * Suggest to use MUST NOT here -> "Multicast Target FEC Stack sub-TLVs
SHOULD NOT be included but .." because you further state that on receiving
it MUST send echo reply as error!

    * In the text "For example, if the egress LSR cannot find the path
specified in the Reverse Path TLV, it MAY establish the BFD session over an
IP network, as defined in [RFC5884]."; it is inappropriate to use MAY for
an example of a configuration option

* Section 4

    * Here as well as section 2 highlights co-routed cases only. But one
can use any reverse path including of a different FEC type. Do we have a
usecase to highlight the need to support different reverse paths? If not
the logical question would be - should one limit the usage?

* Section 6.2

    * The range 192-247 is RFC required and thus you should not say the
allocation is via "Standards Action"! This I-D is also experimental.

* Section 7 should refer to and follow the template of RFC 7942 including
the boilerplate text!

## Nits

* Abstract

    * s/extension to MPLS LSP echo request/extension to the MPLS LSP echo
request/

    * s/system request that the remote BFD peer transmits/system requests
that the remote BFD peer transmits/

    * Expand LSP

* Section 3.2

    * I suggest to not use MUST in this section. It has already been stated
in Section 3.1, this section works best as a listing of return codes

* Section 6.1

    * s/"TLVs and sub-TLVs" sub-registry/"TLVs" sub-registry/

Thanks!
Dhruv

On Mon, Mar 27, 2023 at 2:32 PM <[e-mail]> wrote:

>
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories. This Internet-Draft is a work item of the Multiprotocol Label
> Switching (MPLS) WG of the IETF.
>
>    Title           : Bidirectional Forwarding Detection (BFD) Directed
> Return Path for MPLS Label Switched Paths (LSPs)
>    Authors         : Greg Mirsky
>                      Jeff  Tantsura
>                      Ilya Varlashkin
>                      Mach(Guoyi) Chen
>    Filename        : draft-ietf-mpls-bfd-directed-22.txt
>    Pages           : 9
>    Date            : 2023-03-27
>
> Abstract:
>    Bidirectional Forwarding Detection (BFD) is expected to be able to
>    monitor a wide variety of encapsulations of paths between systems.
>    When a BFD session monitors an explicitly routed unidirectional path
>    there may be a need to direct egress BFD peer to use a specific path
>    for the reverse direction of the BFD session.  This document
>    describes an extension to MPLS LSP echo request that allows a BFD
>    system request that the remote BFD peer transmits BFD control packets
>    over the specified LSP.
>
> The IETF datatracker status page for this Internet-Draft is:
> https://datatracker.ietf.org/doc/draft-ietf-mpls-bfd-directed/
>
> There is also an HTML version available at:
> https://www.ietf.org/archive/id/draft-ietf-mpls-bfd-directed-22.html
>
> A diff from the previous version is available at:
> https://author-tools.ietf.org/iddiff?url2=draft-ietf-mpls-bfd-directed-22
>
> Internet-Drafts are also available by rsync at rsync.ietf.org:
> :internet-drafts
>
>
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