Re: [mpls] [netmod] [Technical Errata Reported] RFC8349 (6251)

["Rob Wilton (rwilton)" <[e-mail]>]

Hi Acee, Tarek, Tom,

Thank for all for your time and help in resolving this issue.

I will reject the erratum.

Regards,
Rob


> -----Original Message-----
> From: Tarek Saad <[e-mail]>
> Sent: 14 August 2020 17:30
> To: Acee Lindem (acee) <acee=[e-mail]>; Tarek Saad
> <[e-mail]>; tom petch <[e-mail]>; Rob Wilton (rwilton)
> <[e-mail]>; RFC Errata System <[e-mail]>;
> [e-mail]; [e-mail]; [e-mail]
> Cc: [e-mail]; [e-mail]; [e-mail]; draft-ietf-
> [e-mail]
> Subject: Re: [mpls] [netmod] [Technical Errata Reported] RFC8349 (6251)
> 
> Thanks Acee. Yes, will do in the next rev we'll push soon.
> 
> Regards,
> Tarek
> 
> On 8/14/20, 12:29 PM, "mpls on behalf of Acee Lindem (acee)" <mpls-
> [e-mail] on behalf of acee=[e-mail]> wrote:
> 
>     Hi Tarek,
>     Can you also add the description of the native MPLS RIB to the text?
>     Thanks,
>     Acee
> 
>     On 8/14/20, 12:27 PM, "mpls on behalf of Acee Lindem (acee)" <mpls-
> [e-mail] on behalf of acee=[e-mail]> wrote:
> 
>         Hi Tarek,
>         This works for me.
>         Thanks,
>         Acee
> 
>         On 8/14/20, 12:25 PM, "Tarek Saad" <[e-mail]> wrote:
> 
>             Hi Acee and Tom,
> 
>             The authors of ID: draft-ietf-mpls-base-yang met and we
> discussed the points below.
>             We understand that RFC8349 defines an AF-agnostic model for
> RIBs. RFC8349 defined only two types of RIBs (IPv4 and IPv6 RIBs), but we
> envision other types of RIBs too (e.g. L2 RIB, MCAST RIB, etc.), in
> addition to MPLS RIB -- and we hope all such RIBs indeed leverage the
> generic RIB model introduced in RFC8349.
> 
>             We revisited Acee's suggestion and made a small modification
> (on top of it) that makes IP routes, MPLS routes (and possibly L2 or MCAST
> routes in future) - all have similar MPLS augmentation (in terms of local-
> label) while still adhering with RFC8349 to augment with leaf destination-
> prefix.
> 
>             augment "/rt:routing/rt:ribs/rt:rib/rt:routes/rt:route" {
>               when "derived-from-or-self(../../rt:address-family, "
>                  + "'mpls:mpls')" {
>                 description
>                   "This augment is valid only for native MPLS routes.";
>               }
>               description
>                 "This leaf augments a native MPLS route.";
>               leaf destination-prefix {
>                 type leafref {
>                   path "../local-label";
>                 }
>                 description
>                   "MPLS destination prefix.";
>               }
>             }
> 
>             We follow same approach for the active route RPC and continue
> to use a leaf "destination-address" as input (that points to a local-label
> leaf).
>             If this is acceptable, we believe the errata 6251 can be
> rejected and we'll proceed with the change in the MPLS RIB model.
> 
>             Regards,
>             Tarek (for authors)
> 
>             On 8/11/20, 9:08 AM, "Acee Lindem (acee)" <[e-mail]>
> wrote:
> 
>                 [External Email. Be cautious of content]
> 
> 
>                 Hi Tom, Draft Authors,
> 
>                 The draft could easily be fixed. You just need to:
> 
>                   1. Expand on the single sentence in section 2.1 on the
> need for non-IP MPLS routes. Given that the draft wasn't modeled
> correctly, this wasn't apparent to most of the reviewers.
>                   2. Add an MPLS AF only augmentation (enforced via a when
> statement) to each route for the MPLS AF specific destination-prefix or
> destination-address.
>                   3. Limit the current local-label augmentation to non-
> MPLS AFs.
>                   4. Limit the active-route augmentation to AF MPLS and
> change the input to destination-address.
> 
>                 Thanks,
>                 Acee
> 
>                 On 8/11/20, 6:10 AM, "tom petch" <[e-mail]>
> wrote:
> 
>                     From: Acee Lindem (acee) <[e-mail]>
>                     Sent: 11 August 2020 10:47
> 
>                     Hi Tom,
>                     I fully understood your original comment. There are
> other problems with this model. See inline.
> 
>                     On 8/11/20, 4:59 AM, "tom petch" <[e-mail]>
> wrote:
> 
>                         Tarek
> 
>                         Picking up on an earlier point,
> 
>                         ________________________________________
>                         From: Tarek Saad <[e-mail]>
>                         Sent: 10 August 2020 21:23
> 
>                         Hi Acee,
> 
>                         The existing RPC is used to query (defined
> AFIs=IPv4/IPv6) RIB to return the matching active route identified by a
> "destination address".
>                         The MPLS module is trying to reuse this RPC so to
> query the MPLS RIB to return the matching active route identified by a
> "local label".
>                         The RPC defined in RFC 8349 readily accepts MPLS
> AFI in it (/rt:routing/rt:ribs/rt:rib/rt:active-route) - unless we augment
> and suppress it with a "when check".
>                         IMO, it is reusable as-is but the text below is
> limiting the leaf name that identifies an entry in RIB to "destination-
> address" only - in MPLS RIB the entry leaf name that identifies an entry
> is "local-label".
> 
>                     It is not reusable as is since the augmentation RPC
> augmentation must have a when statement restricting it to AF MPLS. Also,
> local-label is a leaf which is applicable to all address families. It
> cannot be the AF MPLS destination-prefix. This augmentation is missing.
> 
>                     <tp>
>                     I am probably getting out of my depth here,  On 1may20
> I raised the issue of why the 'MUST' in the description in RFC8349 was not
> enforced in the YANG and 5may20 Martin explained that there is a rule in
> the YANG ABNF of input-stmt that makes the obvious impossible:-(  You are
> raising more profound issues about the RIB that I had not perceived when I
> reviewed mpls-base-yang for which I, and I hope everyone else, will be
> grateful.
> 
>                     If this mpls I-D is to proceed in the immediate
> future, it looks like the action may have to be deferred for future study.
> 
>                     More generally, I think that the interaction of
> forward by address and forward by label is challenging.  When first I
> looked at the MPLS I-D I was surprised at the way RFC8349 was augmented.
> I had not seen MPLS as an alternative to IPv4 or IPv6 or ... in the way in
> which the RFC is used although the RFC does state that it can be; rather,
> to me, labels are a different animal, but I assumed that everyone knew
> what they were doing.
> 
>                     Tom Petch
> 
> 
>                     Thanks,
>                     Acee
> 
> 
>                         <tp>
>                         There should be a 'when' check to enforce the
> 'MUST' but the rules of YANG do not allow it in this structure.  I raised
> this on the NETMOD list at the time of WGLC and Martin pointed me to a
> rule in the ABNF which prohibits such a check.  He also said that the rule
> was not needed and would be a candidate to remove when YANG is revised.
> 
>                         Hence I have always thought of this MUST in the
> documentation as a constraint that must be enforced in the YANG
> 
>                         Tom Petch
>                                 >            action active-route {
>                                 >              description
>                                 >                "Return the active RIB
> route that is used for the
>                                 >                 destination address.
>                                 >
>                                 >                 Address-family-specific
> modules MUST augment input
>                                 >                 parameters with a leaf
> named 'destination-address'.";
> 
>                         Regards,
>                         Tarek
> 
>                         On 8/10/20, 3:27 PM, "Acee Lindem (acee)"
> <[e-mail]> wrote:
> 
>                             [External Email. Be cautious of content]
> 
> 
>                             All (Speaking as an author of RFC 8349),
>                             I just looked at this in more detail and I
> don't think the ietf-mpls.yang model should be augmenting the
> /rt:routing/rt:ribs/rt:rib/rt:active-route RPC. The intent of the RPC is
> to return the address-family specific active-route corresponding to the
> destination-address. This model attempts to overload this RPC with a
> different action all together - returning a route that has the local-label
> as an optional attribute. I'd reject the Errata and believe the
> augmentation should be removed from ietf-mpl.yang. Whether it is replaced
> with a different one is up to the co-authors of ietf-mpls.yang.
>                             Thanks,
>                             Acee
> 
>                             On 8/10/20, 2:29 PM, "Rob Wilton (rwilton)"
> <[e-mail]> wrote:
> 
>                                 [Resend to hopefully pass recipient limit
> filter]
> 
>                                 Hi Tom,
> 
>                                 I would be interested to hear from the
> original authors.
> 
>                                 My impression is that this is a
> technically reasonable change, but I don't think that an erratum can
> create a new revision of a YANG module.
> 
>                                 If this erratum was processed as "Hold for
> document update" then would that be sufficient to do the right thing in
> the MPLS YANG module?
> 
>                                 Regards,
>                                 Rob
> 
> 
>                                 > -----Original Message-----
>                                 > From: tom petch <[e-mail]>
>                                 > Sent: 10 August 2020 17:32
>                                 > To: RFC Errata System <rfc-editor@rfc-
> editor.org>; [e-mail]; Acee
>                                 > Lindem (acee) <[e-mail]>;
> [e-mail]; [e-mail];
>                                 > Rob Wilton (rwilton)
> <[e-mail]>; [e-mail];
>                                 > [e-mail]; [e-mail]
>                                 > Cc: [e-mail]; [e-mail]
>                                 > Subject: Re: [netmod] [Technical Errata
> Reported] RFC8349 (6251)
>                                 >
>                                 > From: netmod <[e-mail]>
> on behalf of RFC Errata System
>                                 > <[e-mail]>
>                                 > Sent: 07 August 2020 16:45
>                                 >
>                                 > <tp>
>                                 > This is the erratum of whose arrival I
> speculated on this list on June
>                                 > 16th.
>                                 >
>                                 > There is a degree of urgency about it.
> The I-D in question is mpls-base-
>                                 > yang, currently in IETF Last Call, which
> is a Normative dependency of bfd-
>                                 > yang which is a Normative dependency for
> a small mountain of I-D which
>                                 > have been waiting a year or so (e.g.
> ospf-yang).
>                                 >
>                                 > I suspect that the technically perfect
> solution would involve a YANG
>                                 > union, choice or some such structure but
> as I said in my Last Call comment
>                                 > I can live with a label that contains
> such as 'address' encompassing such
>                                 > as 'label' in the context of forwarding.
> I take labels to mean what
>                                 > labels mean rather than what I might
> find in a work of reference.
>                                 >
>                                 > Tom Petch
>                                 >
>                                 > The following errata report has been
> submitted for RFC8349,
>                                 > "A YANG Data Model for Routing
> Management (NMDA Version)".
>                                 >
>                                 > --------------------------------------
>                                 > You may review the report below and at:
>                                 >
> https://urldefense.com/v3/__https://www.rfc-
> editor.org/errata/eid6251__;!!NEt6yMaO-
> gk!URK5WVsqD5g7WpzCU1VuzKJA0AUiawXBFLB_gENlsYMrpiMqDtyFoxw8DnSr2A$
>                                 >
>                                 > --------------------------------------
>                                 > Type: Technical
>                                 > Reported by: Tarek Saad
> <[e-mail]>
>                                 >
>                                 > Section: 7
>                                 >
>                                 > Original Text
>                                 > -------------
>                                 > The RPC "active-route" is used to
> retrieve the active route in a RIB.
>                                 > RFC8349 defined two AFIs (v4/v6).
>                                 >
>                                 > draft-ietf-mpls-base-yang is defining a
> new RIB AFI for MPLS as per
>                                 > section 3 in RFC8349.
>                                 >
>                                 > The RPC has a "MUST" statement that all
> RIBs must augment input
>                                 > parameters with a leaf named
> 'destination-address'.
>                                 >
>                                 > For MPLS RIB, it makes sense to augment
> with leaf named 'local-label'
>                                 > since MPLS routes are identified by MPLS
> label.
>                                 >
>                                 > We ask to make the following change:
>                                 >
>                                 > OLD:
>                                 >            action active-route {
>                                 >              description
>                                 >                "Return the active RIB
> route that is used for the
>                                 >                 destination address.
>                                 >
>                                 >                 Address-family-specific
> modules MUST augment input
>                                 >                 parameters with a leaf
> named 'destination-address'.";
>                                 >
>                                 >
>                                 > Corrected Text
>                                 > --------------
>                                 > NEW:
>                                 >            action active-route {
>                                 >              description
>                                 >                "Return the active RIB
> route that is used for the
>                                 >                 destination address.
>                                 >
>                                 >                 Address-family-specific
> modules MUST augment input
>                                 >                 parameters with a
> suitable leaf that identifies the
>                                 > route.";
>                                 >
>                                 >
>                                 > Notes
>                                 > -----
>                                 >
>                                 >
>                                 > Instructions:
>                                 > -------------
>                                 > This erratum is currently posted as
> "Reported". If necessary, please
>                                 > use "Reply All" to discuss whether it
> should be verified or
>                                 > rejected. When a decision is reached,
> the verifying party
>                                 > can log in to change the status and edit
> the report, if necessary.
>                                 >
>                                 > --------------------------------------
>                                 > RFC8349 (draft-ietf-netmod-rfc8022bis-
> 11)
>                                 > --------------------------------------
>                                 > Title               : A YANG Data Model
> for Routing Management (NMDA
>                                 > Version)
>                                 > Publication Date    : March 2018
>                                 > Author(s)           : L. Lhotka, A.
> Lindem, Y. Qu
>                                 > Category            : PROPOSED STANDARD
>                                 > Source              : Network Modeling
>                                 > Area                : Operations and
> Management
>                                 > Stream              : IETF
>                                 > Verifying Party     : IESG
>                                 >
>                                 >
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> 
> 
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